In my opinion these photos show details of Psocoptera (or Corrodentia), not of larvae of Coleoptera. Psocoptera don't live in water, but they can fall down from branches of trees near rivers, lakes an so on, or can be transferred by the wind on the water surface, so becoming prey for fishes. Unlike Coleoptera, Psocoptera are heterometabolous insects (with gradual metamorphosis), so it is difficut to say if the pictures of these fragments regard adult(s) or juvenile stage(s) (nymph(s)). What are the features which suggest my interpretation? A) the shape of the head, the position of eyes, the prominent and rounded postclypeus (see photo 1); the morphology of the antennae, rather well developed (photos 1-3) (and perhaps suggesting a young individual). B) the sclerotization (confused dark spot) within the mouth cavity (Psocoptera have an internal mechanism for chopping solid food), and the shape of the mandibles (photos 1-3). C) diagnostic is, furthermore, the shape of the maxillary lacinia, long and narrow ('baculiform'), in this case clearly bifurcate at the anterior end (see photo 3, on the left side); this is a very peculiar characteristic of the mouthparts in Psocoptera. Finally, also the dimensions are compatible with the size useful for the diet of a very small, young fish: Psocoptera are small insects, adult length is at most a few millimeters, and young individuals, of course, are also smaller than the respective adults. Regards,

Rinaldo Nicoli

Hello dear Catherine, hope you have a nice day.

You will have more pictures of the specimen?. Because they not reached distinguish well the characteristics of the insect.

Best regards

Criss

Hi Christian,

I also have these photo's but I'm not sure they are all the same?

Thanks for your help.

Thanks Rinaldo for your advice and for explaining the key ID features! Incredibly useful!

Dear All,

Rinaldo may be right. The antennae, clypeus, mandibulae as well as the palpus maxillaris are similar to those of Psocoptera however, I could not distinguish the maxillas.

I agree, these 4 further photos also show, in my opinion, fragments of Psocoptera. The third photo (a head) is very clear, you can distinguish the prominent and rounded postclypeus and the maxillary laciniae  with the peculiar shape which is to be found only in Psocoptera. Another consideration: in the photo 3 you can observe clearly, on the left side, a compound eye. When you find a compound eye, the insect can be an adult of holometabolous insects (e.g. Coleoptera), or both an adult and a juvenile stage of an ametabolous or heterometabolous insect, but not a juvenile stage (larva) of holometabolous insects: larvae of holometabolous insects have, in fact, only ocelli (stemmata), not compound eyes.   Regards,

Rinaldo Nicoli

Dear Andras,

among sclerites and appendages which form the maxilla in psocopteran chewing mouthparts, only palps and laciniae (inner lobes) are recognizable in some of the pictures above (for the laciniae see photos 3 and 6); other maxillary parts are too little sclerotized or are covered, so they are not distinguishable. Psocopteran lacinia is long, thin, narrow, and often bi- or trifurcate at the apex: photos 3 and 6 allow to see its borders (as darker lines) and the anterior end, without difficulty. Cordial wishes,

Rinaldo

Ar least some of demonstrated fragments clearly belong to Psocoptera

Dear Rinaldo,

You are right, laciniae can be really recognisable. Thanks for the explication.

I think that these fragments could be Psocoptera as Rinaldo, András, and Dmitry said. I learned a lot about the identification of the group with the explanation of Rinaldo, thanks for this information.

Best regards