One Foot in the Grave

For my job, I routinely have people tell me “oh, I’m too old for this” or “I can’t do this, I’m going to just keel over right here”. We’ll be out on the trail for twenty minutes and already there are the groans and whines and the occasional curses. Sometimes, it’s even the actual elderly folks complaining about being on death’s door.

And after another solid experience with that today, someone claiming they were wholly incapable of walking another inch (they walked another two miles that day, in fact), I remembered something I’d read a long time ago.

Insects feel the same way.

Well, feel might be the wrong term. But they behave that way sometimes. They’ll look at the older folks within their group and try to decide how to best use them in and around the colony. Do you want to put your Auntie Ant in a nice Ant retirement home, safe from the ravages of the world? Perhaps you want to trust Grandma Ant to raise the next generation in her own image with her own words of wisdom?

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This might be the most horrifying thing I’ve ever drawn…

In some Hymenopterans (some honeybees and ant species), there is a pretty firm answer.

They put ‘em to work.

There’s this thing called the Geometric Centrifugal Model of Work, which is a big and fancy sounding thing that breaks down pretty simple.

In essence, the older an individual member of the colony is, the further away from the colony’s center it will do its work. That means essentially the safest jobs are done by the youngest members of the colony, and the most dangerous jobs are done by the oldest members of the colony.

In this case, the safer jobs would be things like brood care or food processing, things that don’t really leave the nest at all. The more dangerous would be things like foraging and defense.

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And when you think about it in an insect context, it makes sense. A lot of time, effort, and resources have been put into taking that individual ant from an egg into a full blown adult. And in some species, they can lose anywhere from 1-10% of the colony in a single day of foraging. Why would you risk hurting that investment before it has a chance to pay the colony back for its resources?

It’s kind of like buying a car. You take it out on the road the first few times and you’re pretty careful. You just made this investment, you want it to last. Maybe you put it into the garage every time a rainstorm is coming. After a few months you skip out on a rainstorm or two, a couple years later you don’t even bother putting it in the garage, and in another decade you’re donating it to a younger member of the family so they have something to beat the snot out of.

For some honeybees it’s a similar system. A typical European honeybee lives about sixty five to eighty days. The first twenty or so of those are spent as an egg, a larvae and a pupa. That’s pretty much when your car is being built in the first place, or when you’re saving up for the car.

From there they will emerge, and spend one or two weeks in brood care (babysitting, yuck) or queen care (still babysitting). After that, its food processing (converting nectar into honey, essentially) then a week or so late they become foragers or field bees. Finally, they will put that sixth foot into the grave and go to the great flower field in the sky.

The vast majority of those field bees will not die of old age. They’ll end up being eaten by something, injured by something, perhaps lost, or caught in some other natural phenomena.

So, long story short, the older you are, the further you go away, and the better chance you have of not making it back. Like a centrifuge, the individual is spun outward away from colony center until eventually they don’t come back.

 

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I need a bigger whiteboard

And to wrap it all up with a nice little bow, it’s all chemically initiated and controlled (at least in bees). That means generally it’s not a big injury or something similar, which in some insects would be a death sentence and in others would just mean you go into retirement. It just happens for no visible reason. It’s almost like that car you just bought had somehow been manufactured to degrade. Like it was planned that this massive investment was to become obsolete.

Wouldn’t it be weird if that actually happened?

 

 

 

Further Reading:

Hölldobler, B., Wilson, E. O., & Nelson, M. C. (2009). The superorganism: the beauty, elegance, and strangeness of insect societies. New York: W.W. Norton.

What is an Insect?

I originally started off writing an article on flight muscles and how exactly an insect stays airborne given the whole “bees break the laws of physics” thing I’ve heard from a few different sources lately, but I don’t want to get too heady too quickly.

Granted, I’d like to get there because I tend to understand things by explaining them, but I don’t want to scare people off just that quick.

We’ll save that to the fifth post or so, aye?

So, let’s make this easy.

This is an insect:

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But this is also an insect:

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And so is this.

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This isn’t.

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Nor is this.

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Colloquially, I hear all of those things called “insects” or “bugs” on a regular basis. And while there are some insects that are technically considered “bugs”, that doesn’t account for all of them. And it definitely doesn’t account for spiders, millipedes, and the like.

So essentially, there are essentially three things that make an insect an insect:

 

  1. Antennae

Heads come in many shapes and sizes, but a lot of creatures have heads. Most of you guys probably all have heads, maybe your house even has a “head” (bathroom). But in this context, the most important features of the head for insect determination are the antennae. They come in a wide variety of shapes and sizes:

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And they all serve important functions, though variable. Many ants will use them a primary means of chemical communication while many dark-adapted insects will use them to make sure they don’t get cornered by similarly dark adapted predators.

 

  1. Six Legs

Sounds pretty straightforward, adult insects should have six legs. Sometimes they are all essentially the same and sometimes the front ones are distinctly different from the back legs, as in a Mantis where the front are designed more like the arms in a monster movie.

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But it’s not always that easy. Take a typical caterpillar for instance, most people would count up their legs and arrive at somewhere higher than eight or ten and be a little perturbed.

But the trick here is that not all of the legs are actually fully functional legs. There are some called “proto-legs” which are less like legs that bend and move (as we’d think of them) and more like a pirate walking around on a peg leg. They serve to help move and balance, but they are not quite the same as having a leg with normal joints.

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  1. Three body segments.

These segments are called the head (the front), the thorax (the middle) and the abdomen (the rear), each with very different shapes, organs, and general styles. The easiest ones to identify are often those of various ants, wasps, beetles, dragonflies and other groups where you can clearly see the distinction between segments.

Again, it’s not always that easy. Things like Stink Bugs, for instance, have a thorax and an abdomen that appear almost fused together. Part of the time that’s purely due to wings covering the spots that would normally be easy to see, and part of the time they just are connected more than others.

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But Chris, there’s “more connected” and then there’s “these are literally the exact same segment all attached”. And there is an explanation for that as well. When a thorax or an abdomen is in different sub-segments of it’s own, it is usually given a letter and number designation. For thoraxes with different parts it’s usually T1, T2 or T3. For the abdomen, the story is the same: A1, A2, A3, A4…

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It’s kind of like humans, really. One person has longer legs, one has a longer torso, one has a squat neck which makes their head seem to be directly attached at the shoulders, and occasionally their waist is skinny enough to appear almost like another section.

It’s hard to make pure 100% true rules for any group of organisms, especially one that has anywhere from half a million to ten million distinct species floating out there in the world.

And of course this whole process can get more complicated. Some insects have two wings, some have four wings, some have no wings, some have wings that don’t really work, some have antennae that are near impossible to see, some mimic non-insects, and some ball up and make it near impossible to tell for sure.

But hopefully this gave you some introduction to the idea of what makes an insect, an insect. Because if you’re going to become a rich (haha) and famous entomologist some day, you should probably figure out what the heck you’re looking for in the first place.

Happy Insecting!