LABORATORY STUDIES ON THE LIFE CYCLE AND BREEDING OF THE MIDGES CHIRONOMUS PLUMATISETIGERUS (DIPTERA : CHIRONOMIDAE)

CHALIOW KUVANGKADILOK

ABSTRACT: The adults of Chironomus plumatisetigerus can be bred in the laboratory for at least 9 generations, by using mating cages 37x37x37 cm³, 30.5x30.5x30.5 cm³, 20.5x20.5x20.5 cm³ and 10.5x10.5x10.5 cm3. The adults will mate readily in a cage 10.5x10.5x10.5 cm³ while only some successful matings between individuals have been obtained in the larger cages. In addition, the number of males in the mating cages seemed to affeCt the success of crosses. For the parental crosses and the F1 self-crosses, at least 25 males were required, while for the self-crosses of F2 and the following generations only 10 males were needed. Laboratory egg masses were collected and checked for fertility and hatchability. The fertility and egg hatchability of the egg masses of F1 and the other generations were rather high (>93%), therefore the laboratory conditions did not seem to affeCt the breeding mechanisms of Ch. plumatisetigerus.

The life cycle of Ch. plumatisetigerus has four stages,as found in other dipterous insects, of which the longest is the larval stage. The head capsule structures of the female larvae are larger than those of the male, so it seems that the male and female larvae have different growth rates.

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Department of Biology, Faculty of Science, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand.

Received June 30, 1994