Corydalidae pupation in captivity

[biggus dickus]

I caught a Nigronia serricornis larvae at a local waterfall ~2 years ago. I have it in a gallon ice cream container with an air bubbler and a rock to squeeze under. It doesnt do much, and I feed it no more than once a month or so. Insect feeders, fish food, blood worms, that kind of thing. I dont change the water, just add more when the level goes down from evaporation. Its shed its skin a few times.

My question is, is it possible to get these to pupate in captivity? or should I just give up on waiting for its behavour to change and throw it back where i found it/ wait for it to die of old age

 

[Salmonsaladsandwich]

Corydalids pupate in a soil chamber on land, so it'll need access to a land area to pupate. Try making a setup with shallow water where you can add some rocks or bricks sticking out of the water covered with dirt and moss for it to burrow in.

It's also possible that it's waiting for certain environmental cues to develop. Putting it in a container of water in a fridge for a few weeks then taking it out might encourage it to start molting and stuff again (the lack of access to a pupation site would obviously be my biggest guess as to why it hasn't pupated, unless it doesn't seem to be near full size).

You also shouldn't underestimate how long it can take stream-dwelling insect larvae to develop. It usually takes several years and I wouldn't be surprised if the life cycle for N. serricornis is naturally more than 2 years. I also wouldn't hold my breath for it to die of "old age", if it keeps being kept in conditions where it survives but can't pupate I can envision it living several more years.

I'm also a little bit surprised its survived so long without water changes considering that N. serricornis seems to only live in habitats with very clean, flowing water. It's possible that the buildup of nitrates from never changing the water could be preventing it from thriving, unless there's live plants/algae in the setup too. I would change the water at least occasionally. It might also appreciate being fed a little more often than once a month, especially if the water temperature is warmer than it would typically experience in a stream.

 

[biggus dickus]

Yes im surprised too with how well its done with so little attention. The water is well oxygenated from the bubbler+there is a healthy layer of gunk, maybe the bacterial community is keeping the water quality acceptable. It just shed recently, thats why its on my mind. I just went and measured it, its 3.5 cm now, which is full size I beleive. I dropped a mealworm in for it.

A set up with sloped gravel going out of the water and some moss on the land he could squeeze under sounds like it would work.

https://downloads.hindawi.com/journals/psyche/1975/051081.pdf this paper says the related species takes 3 years to pupate. If we assume I caught mine in its 1st year, it would pupate this spring. I still dont know what the enviromental cue, if any, needed could be though. temperature? photoperiod? thunderstorms?