Search

Eggs collected from around the base of cultivated cruciferous crops in north-east Scotland were hatched on suitable media contained in petri dishes, or on plants grown in pots in an outdoor insectary. Breeding in petri dishes was more successful. It was found that Erioischia brassicae (Bouché), the cabbage root fly, and E. floralis (Fall.), the turnip root fly, occur together in swede crops, but only E. brassicae in crops of cabbage and cauliflower. Despite the eggs of both species overlapping in size and the chorion patterns being indistinguishable, plotting mean egg sizes over short consecutive periods showed that the main egg-laying period of E. floralis was during August and September. The measurements of eggs collected before and after 1 August, when plotted on arithmetical probability paper, indicated an appreciable difference in the average size of eggs laid in the two periods, but only at those sites where both species were found. [ABSTRACT FROM AUTHOR]