Factors influencing the efficiency of the aphidophagous gall midge, Aphidoletes aphidimyza (Rond.) (Diptera, Cecidomyiidae)

Experiments of the efficiency of Aphidoletes aphidimyza (Rond.) were carried out in the laboratory at 21 degrees C and 75 per cent rel. humidity with its natural prey, the green peach aphid, Myzus persicae (Sulz.) reared either on Brussel sprouts (Brassica oleracea var. gemmifera) or on artificial diet. When preying on 1-2 day-old green peach aphids the total food consumption of the female larvae of A. aphidimyza was higher than that of the males. Larvae of both sexes, however, consumed about 50 per cent of their total food requirements in the last day - fourth day - of their development. Three-day-old larvae were inclined to pupate1675 prematurely, if they were exposed to a period of starvation as short as only a few hours. The percentage of premature larvae inclined to pupate increased with extended period of starvation. Newly emerged females transfered reserve substances accumulated during larval development into egg production within the first two days of the adult life. The number of eggs thus produced was independent on the presence or absence of honeydew and males. The number of eggs produced did not change with increasing aging of the females, if they were supplied with only water. Adult midges of A. aphidimyza take in honeydew of the aphids, which is essential for the maintainance of their life. The life span of the males was, however, always shorter than that of the females. Also the total egg production of the females was significantly increased when honeydew was supplied. Under optimal nutritive conditions in both larvae and adult stage the honeydew intake of the females made out 50-60 per cent of the total egg production, if the single females were kept together with only one male. Another 40-50 per cent could be realized through larval food without honeydew intake of the adults. These percentages varied, however, with the quality of the larval food and the proportion of ovipositing fema