January 20, 2011 | Armonia Nature Preserve, Limon Province, Costa Rica
What do you make of this exuvia? I found it just like this, sticking out of a large downed tree spanning a small creek.
Not sure if you can tell, but there’s a few small horns on the side and then one larger forked horn extending out from the bottom. Whatever left it squeezed out through a split on the top.
It measured 10mm in diameter, and there’s about 18mm extended out of the tree. I carefully pulled the rest out, and it measured 45mm long overall.
The whole thing
Even the rear end is somewhat bizarre looking.
Rear end
Ever seen anything like it? Any guesses as to what left it? A beetle perhaps?
As far as I can tell, all or nearly all beetles have exarate pupae – this highly modified form suggests maybe Diptera? I’ve seen tabanid and mydid fly pupal exuviae protruding from dead tree trunks with weird spikes and spines on the front end.
Thanks for the tips, Ted. I had to look up “exarate”, but now I understand what you mean. I hadn’t considered Diptera. I skimmed the Diptera section of “How to Know the Immature Insects”, but I didn’t see anything similar. I’ll keep digging. The large size and odd appearance of this exuvia really have me intrigued.
It is a timber fly (Pantophthalmidae)puparium. The larvae feed by boring into living wood.
That’s awesome, thanks! Hopefully, I’ll get an opportunity someday to photograph an adult, described elsewhere on the web as “large and robust”. Indeed!