Click Beetle
I was picking up apples in the side yard[1], and found this grub burrowing into one.
These are commonly referred to as “wireworms”. Unlike most other insect grubs, they have a hard exoskeleton that makes them remarkably durable. They are hard to crush, hard to pull apart, and all in all have about the consistency of a piece of wire. They do have legs, which you can see above, but they barely use them and for the most part their behavior is quite wormlike.
There is an interesting feature of their mouthparts, it almost looks like the mandibles are on top of their head instead of underneath, as can be seen below:
The bottom of the head has a complicated structure that looks like it is designed for scraping (you can tell the picture below is of the bottom of the head, because you can see the legs)
When I find these, they are generally rooting around in rich soil looking for organics, or rummaging around in rotted logs. They obviously like apples.
Wireworms are the larvae of “click beetles”, (family Elateridae) like this one:
I doubt that the wireworm is actually the larva of exactly the same species as the adult here, but it doesn’t really matter because all of the Elateridae larvae look about the same as far as I can see. I think that this adult is in the genus Cardiophorus, although I didn’t work through the relevant identification key to make sure[2].
Click beetles have an interesting feature: the junction between their thorax and abdomen is a mechanism that lets them store energy and release it suddenly with an audible “Click!”. When they are stuck on their backs, like this:
they “arch their backs” to cock their click mechanism[3], and then trigger it. This makes them hop into the air about 6-8 inches, and usually land on their feet. They also use this when you try to pick them up: they will click repeatedly. They are pretty hard and slippery, so this makes them very hard to hang onto[4].
The keys to the click mechanism, are, first, that the junction between the thorax and abdomen is very flexible, almost like a hinge, as can be seen from the top:
and on the bottom of the hinge, there is a prong that catches when the hinge is fully flexed. You can see the prong here (it looks like his front leg is stuck under it for some reason)
In general, insects have three body segments (a head, thorax, and abdomen), but click beetles look like they only have two because the head and thorax are pretty much fused together. Even though they look like they have huge heads, the small bit at the front is actually the head, and the rest is the thorax (the eyes are right up next to the anntennae).
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[1] See! They aren’t all in the house! Some of them are outside, getting into our food crops! Incidentally, I was picking up apples to make applesauce. We have about 20 apple trees, with apples that range from pretty decent to eat out-of-hand, to things that taste kind of like vinegar-soaked cotton. Most of them get used to make apple cider (we have a home-made press that can squeeze three bushels of apples at a whack, and produce up to 15 gallons of cider per batch), although the better apples get used for applesauce and pies.
[2] I was going to, but I rapidly started hitting descriptions like “Body castaneous to rufopiceous”, and realized that I wasn’t going to even be able to comprehend this one without a lot more study, let alone actually apply it.
[3] This happens pretty fast, and I wasn’t able to get a picture. Sorry.
[4] Of course, while the clicking might help them escape from predators, it certainly does make them appealing to small children. I used to play with these for hours.
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