Giant Swallowtail Update #1
(click on photos to enlarge)
It’s been 9 days since the Giant Swallowtail (Papilio cresphontes) caterpillars hatched from their eggs. The bad news is that only two survived. The third hatched a day later and after eating part of the eggshell, it half-heartedly nibbled on a leaf and then stopped eating altogether. It remained stationery for several days before it shriveled and died. A number of things could have caused this failure to thrive, among them a viral or bacterial infection passed on by the adult, parasites or just bad genes. The surviving pair are eating well and growing – up to 9 mm at last measure on 4/23. Look at how they’ve changed.
Having shed their birth skins (exoskeletons), the caterpillars have graduated from “first instar” to “second instar.” Since their outer skin can’t expand much, they quickly grow out of it as they gorge themselves on citrus leaves. The only alternative is for the skin to be replaced by a roomier one. The caterpillar stops eating and becomes quiescent for a day while it prepares to replace the tight skin. It does so by splitting along the dorsal (top) surface and then simply crawls out of the old skin. This happens five times during the caterpillar stage.
The photo below shows a second instar caterpillar with the newly-shed first instar skin still semi-attached to the back end.
Leave a Comment