Sviluppo preimmaginale in Euplectus sanguineus Denny (Coleoptera Pselaphidae)

Abstract

PREIMAGINAL DEVELOPMENT OF EUPLECTUS SANGUINEUS DENNY (COLEOPTERA PSELAPHIDAE)

Some 400 wintering adults of Euplectus sanguineus were selected from a single mass of plant debris of agricultural origin (dregs of pressed grapes) in a locality of Southern Italy; they were stored in jars to obtain oviposition. Eggs were discharged in February-March and hatched after 9-10 days; according to the rule in pselaphids, they did change in both shape and corion sculpture meanwhile they developed.

Larvae were fed with collembola (Poduridae) included in a small amount of debris selected from the field substrate. Their development required as many days as follows: 3-4 for first-instar, 3-4 for second-instar, 24- 25 for third-instar. Full-grown larvae led active life for about 20 days; then, they hid among debris on the jar ground and stayed immobile for 4-5 days before pupation. Neither a pupal cell nor a cocoon was built. Pupal time was evaluated on 6 individuals; it was 14-15 days long.

Uova, larve e pupe di Euplectus sanguineus Denny sono state ottenute in laboratorio, a partire da adulti raccolti d’inverno (febbraio-marzo) in un cumulo di vinaccia. Le ovideposizioni sono avvenute entro 20 giorni dalla cattura degli adulti, e le uova sono schiuse dopo 9-10 giorni.

Gli ulteriori dati ottenuti riguardano i seguenti aspetti: (a) variazioni di forma e scultura delle uova in sviluppo, (b) numero e durata degli stadi larvali, (c) attività trofica delle larve, (d) comportamento delle larve in fase di impupamento, (e) differenze morfologiche fra le larve dei tre stadi.

A fronte della constatata presenza di femmine ovideponenti, nessuna larva di pselafide è risultata presente nel medesimo cumulo di vinaccia.

Parole chiave: uovo, larve, pupa, tempi di sviluppo, comportamento.

As those of Euplectus sp. (described elsewhere), larvae of E. sanguineus lack exsertile head organs. Shape and length of their urogomphi are useful characters to recognize each instar.

Key words: egg, larvae, pupa, development time, behaviour.