Hello, I am new to the entomology of aquatic insects. I do enjoy spending time on this site learning about the things I am fishing with. I am confused by the terms used for nymph and larvae. It seems people use the words interchangeably as if they are the same thing. Is this the case? If you take a look at
they show a yellow caddis larvae and the little green rock worm they call a caddis nymph. Thank you for your help.
in general, entomologists in the US use nymph for the non-egg immature stages of hemimetabolous insects. Larvae are the feeding, non-egg immature stages of holometabolous. Stoneflies have eggs, nymphs, and adults (hemimetabolous). Caddisflies have eggs, larvae, pupae and adults (holometabolous). You will still see them both used inconsistently in the fishing literature. And you will often see larva used by entomologists for immature hemimetabolous insects in other countries.
Shawnny3 on Aug 6, 2009August 6th, 2009, 3:46 am EDT
I'm certainly no entomologist, but the distinction easiest for me to remember between these is that the insects that go through a larval stage undergo complete metamorphosis in becoming adults, and those that go through a nymphal stage undergo incomplete metamorphosis. As a fisherman this means to me that nymphs generally look like the adults of that species, whereas larva look way different from the corresponding adults. Even more crudely speaking, the more insect-looking ones are nymphs and the more wormy looking ones are larva.
I'm sure there are lots of entomological shortcomings in my assessment, but that's how I think of them from a flyfishing standpoint.