Handling the tricky stuff

Handling the tricky stuff

Thursday, September 6, 2012

Pudgy on the Outside, Tough on the Inside

Pudgy on the Outside, Tough on the Inside

The hickory horned devil caterpillars have become large and
scary looking, but really they're sweethearts.

Some updates on my rapidly maturing caterpillars. First, the hickory horned devils are beginning to pupate. Thank God! They eat so much that I have run out of reachable limbs  (even by step ladder) on two different trees. I have four out of about 30 survivors currently pupating and more, I'm sure, to follow soon. The mortality in this brood was higher than I expected, but I'll still get a good crop of live pupas. If you would like me to send you a couple, email me at jbhathaw@uncc.edu. Again, I would prefer to send these to kids and/or parents with kids, but if you want some, let me know.

Other than the die-off (mainly when they were little) the hickory horned devils have been relatively easy to raise. When they are ready to pupate, they very helpfully turn from emerald green to blue-green,  which eliminates all worry that you are putting a caterpillar that still needs to eat more into a pupation cage with nothing but dirt.

Luna caterpillars in about 3rd instar. They're tougher than they

Wish I could say the same for the lunas, which were as hardy as all get-out, yet became ornery as they became older. You wouldn't guess this from the cute little florescent green fatties, but they are one tough bug.

I've been astounded with them regarding their appetite. Lunas don't seem to grow any where near as fast as hickory horned devils -- they're currently only in 3rd or 4th instar and about one quarter the size of full-grown horned devils -- but they seem to eat a lot more per caterpillar. They will frequently eat an entire sleeve full of leaves in less than a day. This is a pain, because changing sleeves is a significant amount of work. If you try growing these, definitely use a full bed sheet sized sleeve, which might allow you to not have to move 50 or so caterpillars more than once a week.

But that's not the only reason for using large, linen sleeves. As I've mentioned before, I decided to use nylon screening for my sleeve material during this project because it's hot here in Charlotte, NC in August, and I thought the better air circulation would lead to healthier caterpillars. But last week I had a surprise -- I went to check the luna sleeve and found it riddled with holes. At first I thought a squirrel or a mouse had been at it, but on closer inspection I realized that the caterpillars (about an inch long at that point) had been chewing through it themselves. I caught several hard at work. About 20 or so had staged a jail break and were busy eating on nearby branches outside the sleeve.
Holes the little buggers chewed. Smart, real smart.

I want to stress that nylon screening is not a delicate material -- it's made to replace wire window screens. These little suckers can chew! They're not so bright though -- by making holes in the sleeves and by spending some time outside its protection, a number of them may have doomed themselves. As I've mentioned, parasitic wasps are major predators of giant silk moth caterpillars, and I have no doubt that a few took advantage and laid eggs in some of the lunas. I've already found one that was dying from parasite infection. So it goes -- in farming you have loses because nature is merciless. I've never had this problem before with linen sleeves, so I'd suggest that anyone reading this who wants to try raising caterpillars use that material -- I don't think the luna mandibles can get an handle on the more densely woven material.

Interestingly, I have had no such problem with the hickory horned devils, though they are much, much larger and stronger. Why not? Well, as usual, I don't know, but I do have a guess.  I think the horned devils are adapted to feed on a relatively few number of species that have relatively tender leaves, while the lunas, with their more northern range and much broader range of food plants, are a much more generalist species, and have adaptions that allow them to handle broader food choices, including leaves from some trees with dense, cold-resistant leaves. In other words, the foods they eat require that these caterpillars, soft and chubby as they look, to have strong, capable jaws. Jaws that can clip handily through nylon screening designed to block tougher  bugs.

As I have alluded to before, the hickory horned devils are all bark and no bite -- just soft southern bugs with big hairdos designed to keep them out of fights. Lunas are northern brawlers -- put them in a cage?   Fuggedaboutit.

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