[Ctleps-l] Notes and Questions on Larval Morbidity

Grace Jeschke gjeschke at gmail.com
Sun Aug 5 21:16:42 EDT 2012


My comma caterpillar is sick!



 It had shed its skin by mid-day today (ten days old--3rd or 4th instar? I
lose track). Around 4:30 or 5pm I noticed it had fallen from the leaf it
had been resting on and was lying on its side, unable to grasp with its
legs. There was some green vomit on the leaf and the paper towel where it
had fallen. The thoracic region was extended and the abdominal segments
contracted, and it was heaving slightly and excreting dry frass with
effort. I coaxed the frass out with a paintbrush, and it promptly began
excreting another dry pellet without assistance but with similar effort.
Later it began writhing and contorting into a U. It emitted several drops
of green fluid, and a few orange-brown ones, but I don’t know from which
end. The skin has a greenish tinge where it should be white, but otherwise
it does not look unusual. I’ve attached a photo from today and one from
yesterday for comparison.



Poinar & Thomas, in their 1984 book *Laboratory Guide to Insect Pathogens
and Parasites*, state “loss of appetite, cessation of feeding,diarrhea, gut
paralysis, and regurgitation are characteristic initial stages in many
bacterial infections. Later the insect may appear sluggish (rarely
irritable), have convulsions, and become uncoordinated; a general paralysis
may set in, accompanied by septicemia and death.” This seems a fairly apt
description of my case, but are the symptoms similar in other disease
processes?



Its sibling died in the first 48 hours after barely feeding at all, which
may or may not be related. It was too small to observe much of the events
leading to its demise, except that it also lost grasp in its legs. Could
the pathogen/disease be maternally transmitted, or is ingestion the most
likely route?



I quarantined the caterpillar and removed the vomit, but perhaps not soon
enough. Has anyone tried disinfecting larvae and/or pupae? I have only a
few individuals of common species, but it is always a shame when there’s an
epidemic (fortunately a rare occurrence in my experience). Will the pupae
be susceptible if not infected as caterpillars? I’m probably more inclined
to let nature take its course and hope for the best, but it will be hard to
watch if they all get sick!



Any thoughts or suggestions for a curious observer?



Thanks,



Grace
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