The Natural Control of the Cabbage Caterpillars, Pieris spp.

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Abstract
In New Zealand Pieris rapae is very destructive. A braconid (Apanteles glomeratus), attacking the larvae, and a chalcid (Pteromalus pu-parum), a parasite of the pupae, were imported from England. The efficiency of A. glomeratus in England is largely impaired by hymenopterous hyperparasites. A. rubecula, another parasite of P. rapae, is solitary and emerges when this host is almost half-grown, and the tachinid, Phryxe vulgaris, is viviparous and the larva issues from the chrysalis of P. rapae. P. puparum seems to be invariably a primary parasite. Despite differences in the number of parasite larvae forming the colony, the mature larvae of A. glomeratus almost invariably issued when the hosts had finished feeding and spun their silken carpets on which they normally transform. Host development may be retarded by an increase in the number of parasites attacking ft. Larvae of Pieris brassicae produced an average of 44.7 cocoons; those of P. rapae only 30. The larvae of A. glomeratus consume the fatty reserves of the host but do not inhibit the development of their imaginal rudiments. Factors Limiting oviposition and the numbers of larvae and pupae of Pieris were found to include rain, temp., diseases, insectivorous birds and predacious and parasitic insects. Apparently, the theory of protective coloration does not hold for the pupae of P. rapae.

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