APHIDES.

Hokitika Guardian, 19 March 1925, Page 1

APHIDES.

CURIOUS LIFE STORY. An important step in the solution of one of the most puzzling biological problems that confronts students of crop pests lias been announced in the publication ol the results ol researches on plant lire, carried on by Simon Alareoviteh. entomologist at the Tennessee Stale experiment station.

Riant lire, or aphids, as they are more properly called, have a most peculiar system of reproduction. Each fall, after mating has occurred, the female lays her eggs and dies. In the spring these hatch, and the voting me all females —the plant louse is about the most advanced feminist ill the lower world. These .spring-horn females 11ave III) wings, but may or even all of her first broods of offspring (for she rears many families) may have wings, which enable them to migrate to other plants, frequently at a considerable distance. The really remarkable thing about the spring and summer broods, however, is that the young are produced without lathers. .Males seem to be totally unnecessary in this Adamless insect Ellen all summer long, and these “ pai'thenogenetie ” females have everything to themselves. <" Rartlienogenetie.” by the way, is simply Greek for “ virgin-born.”) But in the fall, when the days grow short, and (hill, males appear among the fatherless children, and the next generation -the eggs that lie in sheltered places over winter—are the results of ordinary matings. ’lhiis tne eyolc is completed. The question has always been, YYhy should males appear in the fall, alter lor. jinr been kept out of the way all summer? The answer commonly accepted now is that the cool wcathei is the stimulus. But Air Aiarcovitcli s experiments indicate that length of dav, and not temperature, is the cause. Aphids kept at summer teniperntllves produced males as soon as the davs grew short in autumn, but when the days in the laboratory were artifieiallv lengthened with electric light the fatherless female generations succeeded each other, even though the temperature was allowed to fall to a low point.

Aii immediate .practical application of his discovery is suggested by Mr Mareuvitcli. The saving of orchards from severe damage depends on inducing the first broods in the spring to migrate from the trees to the other plants on which they find food. .Air Mnrcoviteh suggests that orchards he artificially lighted, just as they now frequently heated, thereby inducing the winged generations, to appear early and " move on ” promptly. Ft might also he worth while to keep up the illumination in the fall preventing the development of males, and thereby also preventing the production of fertiliser! eggs, which alone are able to live over winter.