InsectNet forum

A while ago, I posted a question on the possible function of
a flipper-like outgrowth on the base of the abdomen of Limenitis lorquini
chrysalides. Since then, the leps have eclosed. Both sexes have a cluster
of elongated setae on the base of the abdomen, corresponding to that flipper-like
structure of a chrysalis. Any thoughts about the possible function of these setae?

And nobody has ever noticed this???

Interesting. Presumably this 'hump' occurs in both sexes, if so it is not androconial.

Adam.

Yes Adam, both sexes ... and I believe in all Limenitis, certainly in the 4 or 5 species I've reared.

Liminetis arthemis pupae also have this, anyone have adults handy to look at/ photo?

Igarashi & Fukuda (2000 - The Life Histories of Asian Butterflies vol. 2) illustrate pupae of several Asian Limenitis species, and those all have a similar 'hump'. Interestingly, illustrated pupae of Athyma species have a similar protruberance, but rather more ornate. Lebadea and Moduza species also have it, but somewhat smaller.

Adam.

I checked my wild-caught arthemis, astyanax, and archippus. The abdomen is humped there, though few have much in the way of a tuft of hair. I wonder if it's a wear item that gets lost with age/ use. But the astyanax and arthemis, at least, have a consistent hump, which I'd have just written off as the way it dried. Interesting.

Interestingly, even the larvae of Liminites have a "hump", which is roughly corresponding to the “flipper” found in chrysalides and the cluster of setae in adult butterflies. Here: Full-grown larva of the red-spotted purple Limenitis arthemis astyanax (Fabricius). Photograph by Donald Hall, University of Florida (from https://entnemdept.ufl.edu/).

Surely, somebody must have studies and published on this hump. Right? It is rather obvious. I mean, we have people publishing on Tortricidae, and this is far more interesting.