Cocoons pupae and cofaqui taxonomy

[Robert Dana]

In a post a while back on the topic of cocoons, pupae, etc., Ron Gatrelle included this in his description of the pupal shelter of M. cofaqui:  "The inside of the tube is lubricated with white powder generated from the larva's liquid waste." 

I have never worked with any megathymids, but in several Hesperiinae I have reared (Hesperia, Atrytone, Polites) last-stage larvae develop a glandular patch on the underside of a couple of abdominal segments that produces a flocculent white material that has a waxy character and is strongly hydrofugic. They coat or impregnate the loose silk shelters or cocoons in which they pupate with this material, which looks like a white "powder". I have assumed that this is to prevent the pupa from drowning, as these cocoons are typically on or close to the soil surface. The pupae remain dry and surrounded by a bubble of air even when the cocoon is fully submerged in water. Interestingly, Hesperia ottoe does not develop this patch; does anyone know how unusual this is in the genus Hesperia? All the other Hesperia spp. I have reared (dacotae, leonardus pawnee, assiniboia, uncas) do have this secretory patch. 

I believe that this phenomenon in the Hesperiinae is well-known. Might the "white powder" in the Megathymus cocoon be the same substance rather than a liquid waste product?

Robert

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Robert Dana, Ph.D.
MN DNR
Natural Heritage and Nongame Research Program
500 Lafayette Rd, Box 25
St. Paul, MN 55155
651 297-2367
Email: robert.dana at dnr.state.mn.us
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