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ENTOMOLOGICAL

PROBLEMS

A request for observations concerning the distribution of the Essex Skipper (see Schools Supplement, vol. VIII, Pt. IV, p. 12) led to a discussion at Bury St. Edmunds on 5th March, 1955 upon hybridisation between closely related species and upon the Variation between local races that have evolved in isolation. It was pointed out that the cosmopolitan Painted Lady (Vanessa cardui Linn.), which is widespread over the world and which is a great migrant, varies very little. A great deal of experimental work could be done to determine the dispersal of some of the common species during their lifetime. In many species of moths a scent emitted by the female is capable of assembling males from a considerable distance, and the question of the farthest distance to which the scent can cairy was raised. It has been proved that a male Emperpor moth (Saturnia pavonia Linn.) has travelled more than a mile to a " calling " female, but there is no proof that the scent extended to this distance ; and it is possible that the male, Aying about in a haphazard manner, could by chance approach the female and not pick up the scent tili comparatively close to her. Experiments on this problem would be most valuable but would be difficult to devise. Instances have been noted of the same scents being attractive to different species, which sometimes are not closely related to each other. Cannibalism among larvae was another matter for discussion. This is undoubtedly the habit of the Dun-bar moth (Cosmia trapezina Linn.), the larvae of which habitually feed upon the larvae of other species ; but doubt was expressed upon'the reputed cannibalism of some other species. By way of experiment, a few larvae of the Sprawler moth (Brachionycha sphinx Huf.) had been enclosed with other larvae and without any vegetable food; although this species has a bad reputation, the Sprawler larvae slowly starved to death without attempting to eat their companions. It was suggested that some of those mysterious and unaccountable disappearances of larvae in captivity are often blamed, without sufficient evidence, on cannibalism, and the hope was expressed that rearers would be able to make close observations and try to detect larvae in the act of devouring others.

Entomological Problems  
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