Dear Giuseppe, the stridulation is common in Hydropsyche larvae (Trichoptera). Probably you could interested in this article "Significance of Stridulation in Larval Hydropsychidae (Trichoptera)" Jansson and Vuoristo (1979), Behaviour, 71: 167-185. In this case it seem that the significance of the stridulation in larvae is clear.

Thanks so much.

Dear Dr Montsanto, to answer to the question, I can hypothesize that acustic recalls are udible by the co-specific larvae. If so, it is possible that acustic recalls of larvae that reached a favourable environment may be useful to stimulate other larvae to reach the same environment. Chemical signals give this results in Cirripeds that, as a consequence, adhere in great number to the same substrate. Best regards, Giovanni Pilato.

Many thanks professor Pilato! It's a very interesting discussion, full of details.

A presto e cari saluti,

Gipo

Dear Giuseppe,

if I remember well, larval stidulation is known for Passalidae Coleopterans also, a Group of wood dwelling saproxylics in tropical regions. I need a little more time fo check for this , at the moment I have no access to my library. Best wishes, Pietro 

Thanks so much dear Professor Brandmayr, I'm looking forward to receive some references on Passalidae. Cari saluti, Gipo

G. Grandi (1951, Introd. Studio Entomologia, vol. I, pp. 118-124) reports some cases of sound production in preimaginal stages of insects.  As regards stridulation, beside the case of passalid larvae, it is noteworthy the behaviour of other beetle larvae exhibiting stridulatory organs, e.g. on legs: geotrupid larvae (gen. Geotrupes), lucanid larvae, hybosorid larvae, etc. Among insects which produce sounds by beating or scrubing an area of the body against surrounding surfaces, Grandi reports larvae of the lepidopteran genus Chimabacche (gelechiid moths) and pupae of the lepidopteran genus Eligma (noctuid moths).

The following, more recent publication  deals, for instance, with a geotrupid:

C. Palestrini, M. Zunino, M. Zucchelli, 1990 - Sound production in the larvae of Geotrupes spiniger (Marsham) (Coleoptera: Geotrupidae)  -  Bioacoustics: The International Journal of Animal Sound and its Recording, 2(3): 209-216. DOI: 10.1080/09524622.1990.9753133

 It is less easy to find bibliographic material on the evolutionary and biological meaning of these behaviours.

 Best regards,

 Rinaldo Nicoli

Thank you very much. It's an interesting info. Thanks also for that reference.

Warm regards,

Gipo

larvae of what Giuseppe Montesanto?

Dear Nahid, they're manca stages of terrestrial isopods.