Acquatic insect ID needed Houston, TX

[saleenadam]

I came across a large number of these insects today in a lake I have visited for years that is down to a puddle from our drought. They were swimming right at the waters surface or partially submerged then they would dive below and resurface aanywhere from 5-20 seconds later. They swam very different from any insect i've ever seen by moving back and forth in a diagonal pattern somewhat like a sidewinder rattlesnake. They were incredibly large I would esimate the front (legs/antennae?) to each be about 4-5 inches in length. I have never seen anything like these before. Tried to get a good picture but couldn't get one close for a good focus hoping clear enough for someone to tell what these are. If not will bring a dip net along next weekend to try and catch one for a close up pic.

[thanos]

They look to be nymphs of aquatic Heteroptera in the family Gerridae(Gerris species). These long 'things' on them,are the middle and the hind pair of their legs (not antennae).

Thanos

[bichos]

lol I would have said catfish

[nomihoudai]

Catfish makes sense ! A Gerris sp. of 25 cm legspan ? You sure about that ?

[thanos]

Lol,you are right ! I don't know much about fishes and this 'catfish' hidden in the water,looks like giant Gerris nymphs . The only insect that this resembles is Gerris,so I thought that maybe a big species occurs there.

Thanos

[saturniidave]

I must admit Catfish were the first things to cross my mind. If the pond is down to a muddy puddle they are probably getting a breath of air as the water would be very low in oxygen. Also the 'sidewinder' movement suggests a Catfish with its head on the surface and its body undulating below.
Dave

[saleenadam]

I'd only been able come up with Gerris as well but due to the size and movements had thrown that out. I'll have to try catching one in a net next weekend and see if it actually is a fish below the surface.

[thanos]

saleenadam,no need for trying this - it's definitely a fish .
But I have to say that if someone (like me) doesn't know the position that these catfishes can have in the water in order to breath(as Dave correctly said),with only a small part of their head and the 'moustaches' out of the water to be seen,then he can easily think of Gerris .
I have to admit that,in addition to the very large size for Gerris,before posting about Gerris,some things stuck my mind,like the following: 1.The big distance between the 'legs' of each pair (which are actually the moustaches of the fish here ),which indicates a wide body(actually the head of the fish ),while Gerris have a very slender one.
2.This didn't look like an insect's body. In nature,if I was watching the movements(deeping in the water and again up to the surface),there was no way to confuse it with Gerris of course. When watching at these photos,I was thinking that Gerris stay and move on the surface of the water and don't hide their body in the water.
Anyway,mystery solved,and I learned also something on the catfishes .

Thanos