Note morfologiche su adulti e forme giovanili di Allothrips pillichellus (Priesner) con dati preliminari sul ciclo vitale (Thysanoptera Tubulifera)

Abstract

SOME MORPHOLOGICAL REMARKS ON ADULTS AND YOUNGS OF Allothrips pillichellus (PRIESNER) WITH PRELIMINAR DATA ON ITS LIFE-CYCLE (THYSANOPTERA TUBULIFERA)

In June-August 2001, presence of thrips on the ground was monitored in a small forest of Apulia (southern Italy). Samples were collected by raking and sifting about 1 m2 of soil around the trunk of typical plants of Mediterranean maquis; in the laboratory, they were separately introduced in Berlese’s devices.

Males, apterous females, winged females, neanids (= larvae), prepupae and pupae of A. pillichellus were found. In June-July (10 samples: 67 individuals), sex ratio was 1:1,4; in August (28 samples: 323 individuals) it was 1:14.

Winged females (nearly 3% of all females) were found only in June-July. Many neanids were found in the entire observation period, whereas prepupae and pupae were rarely detected. Only pupae of winged females were surely recognized.

Winged females of A. pillichellus were described so far on the basis of a single specimen; usally, they exhibit 1 pair of “mesosternal lateral setae”, opposite to 3 pairs of these setae found in the apterous females.

The high number of neanids in the samples suggests the life cycle of A. pillichellus to be inclusive of a proliferation period at soil from the end of spring to the entire summer.

Key words: Southern Italy, Mediterranean maquis, sex ratio, winged female rate, seasonal proliferation.

In un boschetto residuale di macchia mediterranea è stata trovata una ricca presenza del tubulifero Allothrips pillichellus (Priesner). Da una serie di 38 campioni di suolo prelevati da giugno ad agosto si sono ottenuti circa 340 adulti, numerose neanidi e qualche individuo degli stadi afagi.

In giugno-luglio si raccolse un numero quasi uguale di maschi e femmine. In agosto le femmine sovrabbondavano sui maschi in proporzione di circa 14:1. Le femmine appartenevano in maggioranza alla forma attera. Alcune femmine macrottere (9 individui) furono reperite solo in giugno-luglio. Non sono stati reperiti individui brachitteri.

Il gran numero di neanidi trovate nei campioni indica che la proliferazione della specie avviene a livello del suolo, almeno nel periodo da fine-primavera a fine-estate.

Parole-chiave: Sud Italia, macchia mediterranea, sex ratio, proporzione femmine attere/alate, proliferazione stagionale.