Diving beetle larvae care?

[MTA]

I got a larva from my pair of Cybister japonicus, and I was wondering how to care for it, I had a batch of Hydaticus grammicus larvae, but none of them reached pupation and they were fed solely bloodworms, do the larvae need a varied diet?

 

[Ranitomeya]

Assuming you were using frozen bloodworms, they probably did not get sufficient nutrition from them--you need live food for the best results. The larvae of both are fluid-feeders and nutrients in frozen foods either leech out into the water or are diluted by water entering them since freezing and processing damages the exoskeleton. You could just toss crickets or roaches of appropriate size into the water as they will go after drowning terrestrial prey.

Pupation is done out of the water in mud or underneath rocks or debris, so you'll have to provide them with a damp area above the water level for them to go to.

 

[Jacob Ma]

You could try searching some local bait or pet shops for some red crawler worms, minnows (depending on their size), and/or tubifex worms. Larvae do not need a greatly varied diet, but its always nice for non-specific dieted species to have some diversity. Especially since diving beetle larvae and adults will pretty much go after any prey they can find and consume.

As for care, I only have a very general idea on how to care for diving beetles, as I only have cared for a few species. The larva's water should be kept clean, as it may succumb very easily (depending on species) to polluted water, and should be provided with floating and sunken decor/plants for cover and "protection." Temperature-wise, the larva should be kept around room temperature, but as a general rule it should never drop below 58-60 degrees Fahrenheit. Larvae are much more difficult to care for apparently than the adults, so just be aware of their conditions.

Here are two general care sheets:
http://shop.minibeastwildlife.com.au/content/Minibeast Wildlife Care Guide - Diving beetles.pdf
https://edis.ifas.ufl.edu/fr398