BIOLOGY OF THE TREE-HOLE BREEDING MOSQUITO AEDES-GENICULATUS (OLIVIER) (DIPTERA, CULICIDAE) IN SOUTHERN ENGLAND

The biology of Aedes geniculatus (O1.) was studied in 1967–73 in Monks Wood National Nature Reserve, an oak-ash woodland, in southern England. Adult emergence from tree-holes occurred from May to September, and the sex ratio was approximately 1:1. Catches on man indicated that the maximum biting densities occurred in July and August and that females spend about two minutes obtaining a blood-meal. Significant positive correlations were found between their unfed weight and the weight of the blood-meal and also between female wing length and fecundity. The mean number of eggs per batch was 70. Studies with bamboo pots used as artificial oviposition sites in the field showed that the seasonal peak in oviposition spanned July and August, daily ovipositional activity was greatest in mid-afternoon and evening and ovipositing females preferred oviposition sites positioned within 4 m of the ground. A small proportion of eggs hatched during the summer in which they were laid, but most hatched in the following spring. Continuous or intermittent soaking failed to induce hatching until this time. In 'the laboratory, partially em'bryonated eggs required a minimum relative humidity of 88% to develop fully, but some embryonated eggs survived at 58%. Some eggs survived for 18–24 months in the field. The sampling of preadult stages dn tree-holes showed that larvae in the first two instars occurred almost throughout the year while third- and fourth-instar larvae were present in spring and summer. Pupae occurred only in the summer. It was concluded that A. geniculatus is univoltine in Monks Wood. © 1979, Cambridge University Press. All rights reserved.