How Many Spiders?

I’ve been sick for a few days now, so I haven’t put any real time into the “what are these fossils” article I promised last time. Instead, let’s look at something comparatively simple. I picked up my son from Kindergarten yesterday. Normally, since I was home and it’s only about a quarter mile, we’d have walked. But, like I said, I’ve been sick. So he’s in the back seat excitedly telling me about his Valentine’s Day party. “Dad?” he asks as we pull into our garage.

“Yes, son?” I respond.

“How many spiders can you carry?”

No, I have no idea where that came from. But I’ve gotten used to that by now. “Well,” I say, “that depends on how big they are, and how cooperative they are.”

So, how many could you carry?

“I could carry a hundred spiders!” he declares.

“Maybe,” I tell him. “If you could put them in a box. Or if they were tiny and well-trained.”

So, how many could you carry? Like I said, it depends on the spider. The good people at Guinness World Records say the Patu marplesi is the smallest spider, while Wikipedia contradicts them and states that a related species – the Patu digua is the smallest. Either way, it’s a tiny spider – the body size is only 0.37 mm – and the author of Catalog of Organisms states that “If one of these spiders crawled into your ear while you were sleeping, it could probably slip into your Eustachian tubes and tap on the back of your eyeballs.” So try not to think too hard about that.

patu-digua

“Peek-a-boo!”

I couldn’t find anything at all about how much (little?) this critter weighs. So, I’m going to run the risk of estimating. Here’s what I did, so that you can play the home game. I found an article titled “Estimating Live Spider Weight Using Preserved Specimens” from The Journal of Arachnology in 1996. It provides a formula for calculating weight from length for spiders: ln weight = 1.844 + 2.711(ln length), and seems to indicate that the weight is read in milligrams (mg) and the length in millimeters (mm). So, that would give us ln weight = -1.844 + 2.711(ln 0.37). That works out to… let’s see…

  1. ln weight = -1.844 + 2.711(ln 0.37)
  2. ln weight = -1.844 + -2.695
  3. ln weight = -4.539
  4. e^ln weight = e^-4.539
  5. weight = 0.010684 mg

So, one 0.37 mm spider appears to weigh 0.01 mg. How many of these could we move? Let’s find out?

Bare Hands

My palm is, roughly speaking, a 9 cm by 9 cm (90 mm by 90 mm) square. That gives me 8,100 mm of surface area, so I could stack a single layer of 8,100/0.37 = 21,891 well behaved Patu digua on one hand. Using both hands, I could carry 43,782 of them. The two-hand load would come out to 0.43782 grams, or 0.0015 ounces of spider.

Let’s try and do more. If I cup my hands, I get a sort of rounded cone that’s 7 cm (70 mm) in diameter by 7 cm (70 mm) deep. That gives me a volume of 359,189 cubic mm. Now, let’s assume that the Patu digua takes up the same volume as a sphere 0.37 mm in diameter. That’s 0.212175 cubic mm. So, in my cupped hands, I could carry 359,189/0.212175 = 1,692,890 Patu digua. Those guys would weigh in at 18.0868 grams (0.63799 ounces).

We’re not savages, you know

Yes, I know. So let’s fill a box. A standard U-Haul shipping box is 41.5″ (1054.1 mm) x 38.5″ (977.9 mm) x 18.75″ (476.25), for a volume of 429,072,327.3375 cubic mm. That means I could carry 429,072,327.3375/0.212175 = 202,256,756 of the little spiders – 21.606 kg (47.6 pounds) of Patu digua. My son weighs more than that, so I know for a fact that I could easily carry that box of spiders from my house to my car, and then from the car to the Post Office, and then from the Post Office back to my car because the USPS would most likely refuse to accept that package.

Cool. What about big spiders?

National Geographic informs me that the South African Goliath Birdeater Tarantula is the biggest spider in the world as measured by body size. Nothing I could find gave me an explicit size, but terms like “puppy sized” and “the size of a dinner plate” were bandied about with distressing familiarity. National Geographic also states that:

Many of the locals in northeastern South America regard T. blondi as a tasty snack. They first singe off the urticating hairs, then wrap the spider in banana leaves to roast it. Tarantula expert Rick West, who once sat down for a meal of these spiders with the local Piaroa people of Amazonas in Venezuela, says T. blondi can be surprisingly tasty and moist. (Also see “UN Urges Eating Insects; 8 Popular Bugs to Try.”)

“The white muscle ‘meat’ tastes like smoky prawns, while the gooey abdominal contents is hard-boiled in a rolled leaf and tastes gritty and bitter,” West says. “The three-quarter-inch [two-centimeter] fangs are used after the meal as toothpicks to remove T. blondi exocuticle from between one’s teeth.”

goliath

“I’m tasty!”

On the other hand, if you’re measuring by legspan the prize goes to the giant huntsman spider, with a leg span over one foot (30.48 cm) across. No word on how they taste, though.

huntsman

“Come on and have a go, if you think you’re hard enough!”

Without specifics, I can’t tell you how many I could handle. One per hand, maybe, and maybe four in a shipping crate. But, on the other hand?  Oh my god no.

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Who Was The First Person?

That was the question my son asked, from the back seat of my wife’s car. I don’t remember the context, but I think we were talking about his grandparents. Things my dad had done, things my wife’s father had done, sharing family stories. That sort of thing. And then he asked it. “Who was the first person?”

That is a hard, heavy question.

What is a “person”?

Merriam-Webster gives multiple definitions for the word “person”:

  1. human, individual —sometimes used in combination especially by those who prefer to avoid man in compounds applicable to both sexes <chairperson> <spokesperson>
  2. a character or part in or as if in a play : guise
  3. a : one of the three modes of being in the Trinitarian Godhead as understood by Christians; b : the unitary personality of Christ that unites the divine and human natures
  4. a archaic : bodily appearance; b : the body of a human being; also : the body and clothing <unlawful search of the person>
  5. the personality of a human being : self
  6. one (as a human being, a partnership, or a corporation) that is recognized by law as the subject of rights and duties
  7. reference of a segment of discourse to the speaker, to one spoken to, or to one spoken of as indicated by means of certain pronouns or in many languages by verb inflection

For these purposes, we’ll focus on the first definition: “human, individual”. Which shouldn’t be a surprise, as it’s pretty clear from the context that my son’s question should be understood as “who was the first human”.

Human beings are formally known Homo sapiens, with contemporary human beings classified in the subspecies Homo sapiens sapiens – a rather arrogant sounding name, since it means “Wise wise man” when translated from Latin. We are part of family Hominidae (also known as “great apes”), a family that includes Homo (us), Pongo (orangutans), Gorilla (gorillas, go figure), and Pan (chimpanzees). Hominidae is part of the Primates, which is an order of the class Mammalia. At present we are, arguably, the most successful branch of both Primates and Hominidae, as we have a globe-spanning range of habitation. We’re certainly the most successful current branch of Homo, as we’re the only extant branch of that genus.

primate-cladogram-2_med

Our family tree

So, who was the first Homo sapiens?

This is where things get tricky, because “species” is a difficult concept to pin down. You’re probably familiar with some version of Mayr’s Biological Species Concept, which defines a species as “groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups”. The problem with this definition, and this is a problem biologists are well aware of, is that nature is “squishy”. Not all species reproduce sexually, for instance. Does that mean they aren’t a species because this concept doesn’t apply? If two different species can successfully breed, even if they wouldn’t normally do so in the wild, does that make them different speices because they’re usually reproductively isolated or does it make them the same species because they can still produce viable offspring? The answer is the subject of a lot of arguments among biologists.

This “squishiness” combines with evolution to make it impossible to pin down a “first” Homo sapiens, or even to say for certain what was H. sapiens and what was a different Homo species. The Neanderthals, for instance, were Homo neanderthalensis, a different species from Homo sapiens, but there is enough genetic evidence to make an argument that they certainly weren’t reproductively isolated from our species. The jury is still out on that, but given some of the other things humans will do today it’s certainly not unreasonable to assume that our ancient ancestors were open to having sex with another species of Homo.

All we can say for certain is that our species differentiated itself from our direct ancestor species – Homo erectus (“upright man” – somewhere between 1.8 million years ago and 200,000 years ago. Which means that we likely overlapped with H. erectus for a significant amount of time, as the oldest fossils of H. erectus are around 1.9 million years old and the youngest are around 70,000 years old. So, worst case, we overlapped with H. erectus by some 130,000 years, which is significantly longer than recorded human history. But we can certainly speculate. There wouldn’t have been a sharp dividing line between H. erectus and H. sapiens, and certainly no moment where a H. erectus mother looked at her baby and said something like “hey, this is different“, because evolution doesn’t work like that.

The lineage that gave rise to H. sapiens would likely just have started off as just another subspecies of H. erectus, like H. erectus erectus (“Java man”), H. erectus nankinensis (“Nanjinj man”) or H. erectus georgicus. That subspecies would have been somewhat geographically and/or culturally isolated from its neighbors – although possibly still indulging in the occasional opportunistic “gene swapping opportunity” – until, over time, it became different enough that it became a distinct organism. Could the new archaic H. sapiens have successfully interbred with H. erectus at that point? Possibly. We could have interbred with H. neanderthalensis, after all. But since all we have left of H. erectus is fossil bones, we’ll probably never know for sure.

That said, genetic studies have indicated that there is something approximating a “first” human man and a “first” human woman.

It’s fun to stay at the MRCA!

MRCA is the Most Recent Common Ancestor, and it’s exactly what it sounds like: the most recent individual from which all members of a set group are descended. For you and your siblings (if you have any), your MRCA is your father and mother. For you and all of your cousins on your mother’s side of the family, your MRCA is your maternal grandparents. And so on. Generally speaking, the larger the group the further back you have to go to get a MRCA. Also, the paternal and maternal MRCA need not always have lived at the same time. Imagine yourself as having a half-brother because one of your parents divorced and remarried. YOu might share a father with the half-brother, making your father the paternal MRCA for that group. But you might have to go back dozens of generations to find a maternal MRCA.

The maternal MRCA for all of H. sapiens is nicknamed the Mitochondrial Eve, and she lived in Africa quite some time ago. How long? well, depending on the type of analysis applied, it could be as long ago as 234,000 years ago or as recently as 99,000 years ago. I won’t pretend to understand the details of how that was calculated, beyond the simple statement that it has to do with mutation rates in mitochondrial DNA – the DNA of the little organelles that our cells use to convert oxygen and sugar into energy. I’m a stockbroker, after all. Not a geneticist or cell biologist.

Our paternal MRCA has been nicknames the Y-chromosomal Adam, and is currently estimated to have lived around 200,000 years ago. Also in Africa, so there is a slim possibility that our paternal and maternal MRCAs knew each other. Don’t count on it, though.

Why Are They Called Theropods?

Every night, before he goes to bed, my wife and I read a book to my son.  Last night, he picked out one of the books he got from the library.  I don’t recall the title, but it was full of cartoon dinosaurs accompanied by facts about them.  A lot of those facts were things I’ve learned in a lifetime of obsession with the “terrible lizards”, and a good number of them are things he’s learned from Dinosaur Train and from other books we’ve read.  But that really isn’t the point of the evening ritual.  If he learns something, that’s great.  For me, though, it’s the opportunity to read to him.

“What’s a theropod?” my son asks.

“It’s a type of dinosaur,” I say, realizing that I’ve forgotten what a theropod is or what the other type of dinosaur is.

“Why is it called a theropod?” he continues.

“I don’t know,” I tell him.

“Can you find out?”

Of course I can.

Dinosaurs!

Let’s start off with the basics.  You may have heard that dinosaurs aren’t reptiles.  This is not strictly true, as Dinosauria is a clade of the class Reptilia – a class that in modern times includes turtles, crocodilians, snakes, amphisbaenians (aka worm lizards), lizards, and tuatara.  Dinosauria contains two Orders, Ornithischia (primarily herbivorous dinosaurs with a hip structure similar to birds) and Saurischia (primarily carnivorous dinosaurs with a hip structure similar to lizards), although it appears that many contemporary paleontologists classify Ornithischia and Saurischia as clades rather than orders.

Clades?

A clade can be thought of as a branch on the tree of life.

tree-of-life_2000

More specifically, a clade consists of a single ancestor species and all the species that evolved from it.  In broad strokes, all life is a clade because everything traces back to a single organism.

Theropods?

“Theropod” derives from Greek, and means “wild beast foot”, and was coined in 1881 by O. C. Marsh as a suborder to hold Allosaurus.  They are ancestrally bipedal, ancestrally carnivorous dinosaurs – “ancestrally”, because some species of theropods evolved omnivorous or herbivorous diets, or quadrupedal gaits, or both.  Depending on the “age” of the species and the specific lineage they may have had scales or feathers or both.  The order includes many of the famous, “sexy” dinosaurs, such as the Tyrannosaurus Rex, the “four-winged” Microraptor, and chickens.

Chickens?

Yes, chickens.  See, one clade within Theropoda was Averostra (“bird snouts”), and Averostra had a couple of clades survive the Cretaceous–Paleogene extinction event:  Ceratosauria and Orionides.  Within Orionides was the clade Maniraptoriformes, which was the parent clade for Avialae, which was the parent clade for Aves – modern birds.  So, yes, birds are “lizard-hipped” dinosaurs.  Go figure.

dinosaurs

Why Does A Stinkbug Stink?

“Look, dad!” my son shouts, voice excited as he points. “A stinkbug!”

We’re walking up the front stairs to our condo. I glance in the direction he’s pointing, and see nothing.  “Cool,” I tell him.

“Why do stinkbugs stink?” he asks.

I unlock the front door. “I don’t know,” I answer. “I think maybe they spray stinky chemicals.”

What is a stinkbug?

Getting information on stinkbugs in general proved to be a little difficult, as Google just keeps giving me hits for the Brown Marmorated Stink Bug (Halyomorpha halys), an insect native to China and Japan that is an invasive species in North America.  Wikipedia, when you do a search for ‘stink bugs’, takes you to a page about family Pentatomidae, a family of insects belonging to order Hemiptera.  Shield bugs and stink bugs belong to Hemiptera, with stink bugs comprising Pentatomidae.

I couldn’t find a list of the species native to North America.  Heck, I couldn’t even find a list of the species of Pentatomidae, end of statement.  But, here’s a brown stink bug that is native to this continent:

native_brown_1242026

That particular bug is Euschistus servus, and it is a common pest throughout southern Canada and the northern United States.  This particular bug is about half an inch long (10 to 15 mm), and lays a bright yellow egg mass (around 60 eggs) that turns pinkish as they get ready to hatch (between four and five weeks after being laid).  Larval stink bugs require about 29 days to reach maturity.  Adults are able to fly, and are primarily omnivores.

Brown stink bugs often feed on the vegetative parts, flowers, stems and foliage of the plant, as well as the seed, nut or fruit, and this makes them important pests of many crops.

Brown stink bugs are found on a variety of hosts, such as shrubs, vines, many broadleaf weeds, especially legumes, as well as cultivated crops such as corn, soybean, sorghum, okra, millet, snap beans, peas and cotton.

Do stinkbugs stink?

Yes, they do.  Here’s what Orkin has to say on the subject:

Their name comes from their smelly defense mechanism. Stink bugs have the ability to emit a strong deterring odor, from their body glands, whenever they feel threatened or injured — much like how a skunk defends itself. The smell varies depending on the species and the person’s olfactory senses, but it has often been compared to strong herbs and spices like cilantro and coriander.

Interesting enough, the composition of the odor is comprised of chemicals commonly used as food additives and is present in cilantro. This smell can linger for hours so, if possible, try to avoid stink bugs or carefully sweep or vacuum them up if they have entered your house, unless you want a face full of intense-smelling herbs and spices.

A more detailed description of the specific chemicals used by one particular species of stink bug may be found in Chemical Defense in the Stink Bug Cosmopepla bimaculata, an article published in the Journal of Chemical Ecology back in 1999 and freely available on the internet.  From the abstract,

Adult Cosmopepla bimaculata discharge a volatile secretion from paired ventral metathoracic glands (MIG) when disturbed. Collected volatiles were similar in both sexes and consisted of n-tridecane (67%), (E)-2-decenal (12%), (E)-2-decenyl acetate (12%), (E)-2-hexenal (3%), hexyl acetate (2%), n-dodecane (2%), a tridecene isomer (l%), and n-undecane, n-tetradecane, and n-pentadecane (all <1%). In addition. undisturbed males produced a novel insect compound. (E)-8-heneicosene. whose function is unknown.

No, I don’t know what any of those are.  But every resource I found agrees on a few things about stink bug spray:

  1. It smells vaguely of spices and cucumber
  2. Despite that, it does not smell good.
  3. No, really, it stinks like old garbage.

So, to answer the original question, why do stink bugs stink?  Because they don’t want to get eaten.  Again, as the abstract of Chemical Defense in the Stink Bug Cosmopepla bimaculata put it, “In feeding trials, killdeer (Charadrius vociferus), starlings (Sturnus vulgaris), robins (Turdus migratorius), and anole lizards (Anolis ccarolinensis) rejected or demonstrated aversion to feeding on the bugs. Furthermore. bugs that lacked the secretion were more susceptible to predation than bugs with secretion, suggesting that the secretion functions in defense against predators.”

 

Why are there bugs in his hair?

My son attends a preschool, and we just found out that head lice are going around. This was a source of some concern for my son, because what he knows about it starts with “bugs in hair, bugs in hair!” and ends with “they make you itch!” So, naturally, he’s had some questions about them. Lots of questions. And, to tell the truth, so do I. Because I remember distinctly that, when I grew up, there was a social stigma associated with having lice. Not just because you had bugs in your hair, but because it meant you were perceived as filthy and dirty.

That’s hardly a fair assumption, of course. My son’s daycare and preschool is a wonderful place and they take hygene seriously. But it’s hard to shake beliefs that get ingrained during childhood. Also, it turns out that I know next to nothing about head lice. Beyond “bugs in hair, bugs in hair!”

What are head lice?

head-lice

That picture up there? That’s a head louse – Pediculus humanus capitis – an obligate ectoparasite of humans, which is a fancy way of saying it’s a parasite that lives on human skin and needs to exploit a host as part of its life cycle. Pediculus humanus capitis feeds by biting the skin and injecting an anti-coagulant in order to suck blood (producing a dark red poop when digested), and generally colonizes the scalp (particularly the nape of the neck and the back of the ears).

lice_lifecycle

According to the CDC,

The life cycle of the head louse has three stages: egg, nymph, and adult.

Eggs: Nits are head lice eggs. They are hard to see and are often confused for dandruff or hair spray droplets. Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the scalp. They are 0.8 mm by 0.3 mm, oval and usually yellow to white. Nits take about 1 week to hatch (range 6 to 9 days). Viable eggs are usually located within 6 mm of the scalp.

Nymphs: The egg hatches to release a nymph. The nit shell then becomes a more visible dull yellow and remains attached to the hair shaft. The nymph looks like an adult head louse, but is about the size of a pinhead. Nymphs mature after three molts and become adults about 7 days after hatching.

Adults: The adult louse is about the size of a sesame seed, has 6 legs (each with claws), and is tan to grayish-white The number 5. In persons with dark hair, the adult louse will appear darker. Females are usually larger than males and can lay up to 8 nits per day. Adult lice can live up to 30 days on a person’s head. To live, adult lice need to feed on blood several times daily. Without blood meals, the louse will die within 1 to 2 days off the host.[/quote]

Wikipedia expands on the definition of “nit” a little, stating that “the term nit refers to an egg without embryo or a dead egg”.

Pediculus humanus capitis requires anywhere from 8 to 24 days to mature from a newly-hatched nymph to a sexually mature adult, depending on temperature and access to blood. Once mature, a female can lay 3-4 eggs per day for pretty much rest of her life (which can be up to 30 days from hatching). This is under optimal conditions of course.

Ick. So, how does it spread?

Turning to the Centers for Disease Control once more,

Head lice are mainly spread by direct contact with the hair of an infested person. The most common way to get head lice is by head-to-head contact with a person who already has head lice. Such contact can be common among children during play at:

  •  school,
  • home, and
  • elsewhere (e.g., sports activities, playgrounds, camp, and slumber parties).

Uncommonly, transmission may occur by:

  • wearing clothing, such as hats, scarves, coats, sports uniforms, or hair ribbons worn by an infested person;
  • using infested combs, brushes or towels; or
  • lying on a bed, couch, pillow, carpet, or stuffed animal that has recently been in contact with an infested person.

Reliable data on how many people get head lice each year in the United States are not available; however, an estimated 6 million to 12 million infestations occur each year in the United States among children 3 to 11 years of age. Some studies suggest that girls get head lice more often than boys, probably due to more frequent head-to-head contact.

Interestingly, they note that (in the United States, at least) African-Americans are less likely to have an infestation than other races. They don’t quite know why, but speculate that the most common head louse in the United States is not well adapted to grasping the shape and width of some types of hair. Sadly, if you’re African-American and reading this, you can’t simply assume that you’re immune to head lice infestations. After all, “less likely” is not the same thing as “can’t get it”.

The CDC also states the following: “Head lice move by crawling; they cannot hop or fly. Head lice are spread by direct contact with the hair of an infested person. Anyone who comes in head-to-head contact with someone who already has head lice is at greatest risk. Spread by contact with clothing (such as hats, scarves, coats) or other personal items (such as combs, brushes, or towels) used by an infested person is uncommon. Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice.” To be safe, you probably still don’t want to share hats or combs or the like. But you should really avoid headbutting.

How do I know if I (or someone else) has lice?

Unsurprisingly, the CDC has a lot to say about this. Symptoms include:

  • Tickling feeling of something moving in the hair.
  • Itching, caused by an allergic reaction to the bites of the head louse.
  • Irritability and difficulty sleeping; head lice are most active in the dark.
  • Sores on the head caused by scratching. These sores can sometimes become infected with bacteria found on the person’s skin.

However, they also note that “Misdiagnosis of head lice infestation is common. The diagnosis of head lice infestation is best made by finding a live nymph or adult louse on the scalp or hair of a person…. If crawling lice are not seen, finding nits attached firmly within ¼ inch of the base of hair shafts suggests, but does not confirm, the person is infested. Nits frequently are seen on hair behind the ears and near the back of the neck. Nits that are attached more than ¼ inch from the base of the hair shaft are almost always non-viable (hatched or dead). Head lice and nits can be visible with the naked eye, although use of a magnifying lens may be necessary to find crawling lice or to identify a developing nymph inside a viable nit. Nits are often confused with other particles found in hair such as dandruff, hair spray droplets, and dirt particles.”

Yeah, that’s distinctly a bug. Now what?

Are you shocked to learn that the CDC has information on this as well? No? Me neither. The first thing that they recommend is, after confirming that someone in the household has an active infestation, you should check everyone else in the same household. It’s most likely to spread within a family, after all, as family members have the greatest odds of coming into head-to-head contact.

Pharmacologically speaking, you can use an over-the-counter or prescription medicine to kill the lice and nits. Be sure to follow the directions and, if the infested individual has long hair, consider more than one treatment. The CDC also recommends not re-washing hair for one to two days after treatment, to allow the residue of the medicine to continue to work. After treatment, comb the infested individual’s hair thoroughly to remove lice and nits and then check them around 8-12 hours after treatment. A few live but sluggish lice found during that time generally doesn’t mean that the treatment failed (some are more resistant than others), and you probably won’t need to retreat. If the lice are still active,, however, you may wish to use a different medicine and/or consult with a health care professional. Also, even after the lice appear gone, you should comb the hair with a nit comb every two to three days for the next two to three weeks to ensure the infestation is gone. Also, if the specific medicine you are using has different instructions, follow them.

Any clothing, bed linens, plush animals, etc that the infested individual came into contact with should be washed on hot (130 degrees F or higher) and then dried on the high heat cycle. Items that are not machine washable can be dry-cleaned instead, or sealed in plastic bags for two weeks. Vacuuming furniture and carpets can remove any lice that have fallen from the infested person, but they generally do not survive long off a human (since they are human-exclusive parasites that need human blood to live) so you don’t have to go to extreme measures to sterilize your home.

Kill it. Kill it with fire!

Generally speaking, you don’t actually kill head lice with fire. Not that it wouldn’t work, mind. But they’re living on your skin, so you don’t really want to apply fire. Instead, you apply neurotoxins.

Yes.  Neurotoxins.

The most common over-the-counter medicines for head lice are pyrethrins, which kill by “targeting the nervous systems of insects”. Specifically, “pyrethrins delay the closure of voltage-gated sodium ion channels in the nerve cells of insects, resulting in repeated and extended nerve firings. This hyperexcitation causes the death of the insect due to loss of motor coordination and paralysis.” So, yes. You’re consigning the little bugs to a slow and agonizing death. But it also functions as an insect repellent, driving survivors from the treated area – sort of the over-the-counter version of displaying your enemies’ heads on pike, I guess.

Note that pyrethrins can affect humans, in sufficient doses. The EPA recommends different daily oral exposure limits for pyrethroids of anywhere from 0.005 to 0.05 mg per kg per day (depending on the specific pyrethroid), and OSHA has set an occupational exposure limit for a standard work day of 5 mg per cubic meter. Note, however, that most lice treatment shampoos run around 0.33% pyrethrins by weight. What does that mean?

well, I weigh 133.35 kg, meaning that my safe limit for daily oral exposure to pyrethroids ranges from 0.66675 mg to 6.6675 mg per day, depending on the specific pyrethroid. Assuming the specific pyrethroid in the medicine is the one in the 0.005 mg per kg limit, I could drink 202 mg of the medicine and generally be all right. (Note: do not do this!) That’s not a whole lot, though, which is why these medications fall under the category of “safe when used as directed“.

Head lice medication cocktails are not a use as directed.

What Do Lobsters Do?

A while back, we were out grocery shopping. My son really enjoys this (sometimes) because I let him get involved. He gets to pick out some of the fruit we buy, and he asks questions, and he gets to go look at the lobster tank. This last part is huge for him, because the lobster tank at the local grocery is a big cylinder sitting out in the aisle. And it has benches next to it, so you can sit and look at the lobsters. Or, if you’re five, so you can climb up and press your face to the plexiglass and stare at the lobsters in fascination. I’ve told him that they’re there so people can buy them and eat them, but he still regards it as a huge aquarium.

So we’re sitting and looking at the lobsters, taking a short break before we get back to the shopping. And he’s tapping on the glass, and staring at the lobsters, and asking questions. “Why are they in there?” “Why do they have rubber bands on their hands?” Things like that, easy questions.

“What do lobsters do?” he asks.

What? What does that even mean? So, I ask him. “What do you mean?”

“What do lobsters do?” he repeats, his voice incredibly patient.

“Like, what do they eat?”

“No, daddy,” he repeats, enunciating. “What do lobsters do?”

That’s a pretty heavy question. Let’s see if I can’t answer it.

What is a lobster?

Let’s start at the beginning. What, exactly, is a lobster?

lobster

This. This is a lobster.

Sure, I’ve seen pictures of them. And I’ve seen them in grocery stores, and at the aquarium. And that’s about as far as my knowledge goes. I think I’ve always assumed that they were oceanic bugs, maybe related to crabs, and then I went on with my day. They never really caught my attention the way dolphins or sharks or cuttlefish ever did.

The answeer is a bit tricky.

See, lobsters are crustaceans, a class of creature defined by the Encyclopedia of Life as belonging

to the phylum Arthropoda, as do insects, arachnids, and many other groups; all arthropods have hard exoskeletons or shells, segmented bodies, and jointed limbs. Crustaceans are usually distinguishable from the other arthropods in several important ways, chiefly:

  • Biramous appendages. Most crustaceans have appendages or limbs that are split into two, usually segmented, branches. Both branches originate on the same proximal segment.
  • Larvae. Early in development, most crustaceans go through a series of larval stages, the first being the nauplius larva, in which only a few limbs are present, near the front on the body; crustaceans add their more posterior limbs as they grow and develop further. The nauplius larva is unique to Crustacea.
  • Eyes. The early larval stages of crustaceans have a single, simple, median eye composed of three similar, closely opposed parts. This larval eye, or “naupliar eye,” often disappears later in development, but on some crustaceans (e.g., the branchiopod Triops) it is retained even after the adult compound eyes have developed. In all copepod crustaceans, this larval eye is retained throughout their development as the only eye, although the three similar parts may separate and each become associated with their own cuticular lens. In other crustaceans that retain the larval eye into adulthood, up to seven optical units may develop.
  • Labrum. Crustaceans have a lobe-like structure called the labrum anterior to the mouth that partially encloses it.
  • Head. Crustaceans are distinguished by a five-segmented head (cephalon), followed by a long trunk typically regionalized into a thorax and abdomen.
  • “Baby teeth.” Most crustaceans in their early larval stages chew their food with a unique structure called a naupliar arthrite, which is on the second antenna. This chewing tool is lost later in development, and chewing is taken over by the mandibular gnathobase.

Wikipedia adds that crustaceans include crabs, lobsters, crayfish, shrimp, krill, barnacles, and “all animals in the Pancrustacea clade other than hexapods” (with hexapods meaning insects). So, you really could argue that lobsters are bugs. They’re just not insects.

But wait! It gets even more complicated!

True lobsters are part of the Nephropidae family. They’re part of the Animalia kingdom (making them animals), the Arthropoda phylum (meaning they’re invertebrates with exoskeletons and segmented bodies), class Malacostraca, order Decapoda (meaning “ten-footed”). At present, fourteen different genera of Nephropidae are known, with a total of 54 different species. Out of those, if you’ve eaten one, it was most likely Homarus americanus (the American lobster, found on the Atlantic coast from Labrador to New Jersey) or Homarus gammarus (the European lobster, found along the eastern Atlantic coast of Europe, as well as the Mediterranean and Black Seas).

Related Decapodae are the spiny lobsters (family Palinuridae), the slipper lobsters (family Scyllaridae), furry lobsters (family Palinuridae), and squat lobsters (which are actually more closely related to hermit crabs). None of them are considered to be true lobsters.

Great. So what does a lobster [do?

There’s 54 different species, each of which does its own thing. In general they are benthic omnivores, meaning they live on the sea floor and eat whatever they can find. Fish and mollusks make up the majority of their diet, but they’ll eat algae, sea plants, and even other lobsters if they need food – although cannibalism appears to be a response to population pressures and is not believed to be a primary strategy. As benthic animals, they primarily walk (using eight of their ten legs for locomotion). They can swim as well – backwards – as an escape mechanism if needed. Swimming speeds of up to 11 mph (17.7 kph) have been recorded.

Lobsters, like most crustaceans, have to molt (shed their exoskeleton) in order to grow, something which is part of their reproductive cycle – males and females mate after the female has molted and while here carapace is still soft. The female stores the sperm for up to a year before fertalizing and laying eggs, which she will carry curled in her tail her tail for another 9 to 12 months before they hatch. At hatching, the female uncruls her tail and allows the surviving eggs to be exposed to the water so the larvae can float free.

Larval lobsters are planktonic, swimming near the surface as they go through three stages of development (named stages I through III). Stage III ends with the third molt, when the post-larval lobster finally resembles a lobster and settles down to the sea floor. The young adult lobster spends much of its time hiding and feeding at night, when predators are less likely to find and eat it. As they age and grow, they travel further to feed and begin to stake out a territory. Then, once they reach sexual maturity, the process starts over.

So, what do lobsters do? Pretty much what all other animals do: eat, sleep, grow, and breed.

Why Didn’t Buffaloes Go To Heaven?

My son asked me that question right out of the blue one day. I think I might have been cooking dinner, and he just walks over and asks “why didn’t buffaloes go to heaven?” I’m pretty sure my answer was a largely unintelligible “unh?” Followed by some quick thinking – not to mention wondering if this was going to be a “do animals go to heaven” kind of question – and then a counter-question of my own. “What do you mean?”

Hey, they can’t all be winners.

He thinks about that for a moment. “Why didn’t they die when the others did?”

Others? Now I’m even more lost. What on Earth is he talking about?

“The saber-tooths!” he informs me. “Did they run away from the poisonous gas?”

And suddenly, it all clicks. He knows the dinosaurs went extinct, but he’s settled on the idea that it was poisonous gas that did them in. I think that comes from a dinosaur program we watched (I don’t recall which one) that showed a bunch of dinosaurs dying in a limnic eruption. So, he’s asking why dinosaurs didn’t go extinct when the saber-tooths did. Which is not a bad question at all.

Why did saber-toothed tigers go extinct?

At one point, it was a popular theory that saber-tooth cats went extinct because they were ‘superpredators’ that were too successful and wiped out their prey. After this, they starved. Recent studies, however, seem to contradict this. In Implications of Diet for the Extinction of Saber-Toothed Cats and American Lions, researchers examined wear patterns of teeth and jaws for animals recovered from the famous La Brea tar pits with those of living large carnivores. In tough times, our living large carnivores will put more effort into “bone consumption” – cracking and chewing bone for whatever nutrition can be obtained, and the research team believed it was reasonable to assume that extinct large carnivores would exhibit the same behavior. The results of the study?

DMTA here suggests that extinct carnivorans at La Brea may have utilized carcasses less than do some carnivorans today. This idea is inconsistent with interpretations of high incidences of tooth breakage in extinct Pleistocene carnivorans from La Brea compared with extant taxa. We suggest that tooth breakage data may be recording damage from both carcass utilization and prey-capture, with greater tooth breakage occurring due to increased prey size. Lower mean values for DMTA attributes consistent with greater durophagy (i.e., Asfc and Tfv) in both S. fatalisand P. atrox compared with both P. leo and C. crucuta, suggest that the late Pleistocene at La Brea was not any “tougher” (or perhaps “harder”) than the African savanna is today. Further, dental microwear texture comparisons through time offer no evidence that carcasses were utilized consistently more over time, especially for P. atrox. Thus, DMTA provides no support for the idea that prey-resources became scarcer over time. While competition with humans for prey is unlikely to explain the extinction of P. atrox and S. fatalis via competition for prey resources at La Brea, further work is necessary to assess the situation at other sites. Collectively, there is no evidence for greater carcass utilization during the Pleistocene; however, high levels of anterior tooth breakage could instead result from hunting megafauna and/or conspecific competition at La Brea. Thus, times may have been “tough,” but not as originally proposed.

So, what did kill them?

The Quaternary extinction

The Quaternary extinction is the name given to the mass extinction between 40,000 and 10,000 years ago. It impacted every continent to a greater or lesser degree, and in North America it rendered the majority of all animals over 44 kg (100 lbs) extinct. Nobody’s quite sure why it happened, but there are several hypotheses:

  • Hunting: human predation wiped the megaherbivores out, and then the megapredators starved because they couldn’t eat enough prey to make up for the calorie count of hunting. Like all hypotheses it has supporters and detractors. The supporters point out a strong correlation between human arrival and extinction (particularly in Australia and New Zealand), while detractors point out that (for example) most of the North American megafauna were already extinct before humans are known to have arrived. Also (in North America) one megafaunal species that was a human prey species (bison) did not go extinct.
  • Climate change: either an ice age or the end of an ice age drive the extinctions.
  • Hyperdisease: humans and/or the animals travelling with them brought diseases that the local animals were not able to adapt to.

All of these arguments have multiple and ongoing arguments for and against them. The only clear scientific consensus is that the Quaternary extinction did happen. Barring some sort of smoking gun (aliens calling us and telling us they wiped out all the giant sloths, for instance), there will probably never be a clear consensus. My gut feeling is that it’s some mixture of predation and climate change and disease all hitting in some sort of extinction-level perfect storm, but that’s just me.

Bison

So, with apologies to my son, the better question might be “why didn’t the buffaloes go to heaven?” After all, North America lost 33 of 45 genera of large mammals – including wild horses, tapirs, camels, giant beavers, giant tortises, some really huge birds, and ground sloths. Why did the bison survive?

The answer is that they almost didn’t. Before the Quaternary extinction, there were five distinct species of bison in North America: the ancient bison (Bison antiquus), the long horned (or giant) bison (Bison latifrons), the steppe bison (Bison priscus), the American bison (Bison bison), and Bison occidentalis. The giant bison went extinct between 30 and 20 thousand years ago, during the Quaternary extinction. The ancient bison lived until about 10,000 years ago, and was the ancestor of the American bison, and the steppe bison went extinct around the same time. B. occidentalis went extinct around 5,000 years ago, and was most likely bred out of existence (DNA studies have demonstrated that they interbred with what became the American bison).

Of course, even after surviving the Quaternary extinction, they very nearly still went extinct. By 1900, they had been so extensively hunted that there were only 39 bison left alive in the United States, all residing in Yellowstone National Park. They’ve recovered with extremely careful management, but a population of 75,000 is a minuscule fraction of the pre-European bison population. So maybe the “hunting’ hypothesis for the Quaternary extinction isn’t so outlandish.