William Edward Garrett Fisher, 1911 Encyclopædia Britannica (1911)
“ As the summer wears on a second form of insect appears amongst the root-dwellers, though hatched from the same eggs as the form described above. These are the nymphs, destined to acquire wings; their body is more slender in outline, and at first they bear well-marked tubercles. After several moults the rudiments of two pairs of wings appear, and then the insect creeps up to the surface of the earth, and on to the vine. ”
William Edward Garrett Fisher, 1911 Encyclopædia Britannica (1911)
“ The life of these sexual forms lasts but a few days, and is entirely taken up with reproduction. The female is fertilized by the male and three or four days later lays a single egg—the winter egg—and then dies. This egg is laid in the crevices of the bark of the vine, and as it is protectively coloured it is almost impossible to find it. Here the winter eggs remain undeveloped during the cold months; but in the following spring, as a rule in the month of April, they give birth to a female insect without wings, which resembles the root dwelling forms, but has pointed antennae. ”
William Edward Garrett Fisher, 1911 Encyclopædia Britannica (1911)
“ If, however, the insect were content with this method of reproduction the disease could be isolated by surrounding the infected patches with a deep ditch full of some such substance as coal-tar, which would prevent the insects spreading on to the roots of healthy vines. The fertility of the parthenogenetically produced insects would also diminish after a certain number of generations had been produced. ”
