74 Observations on Insects affecting the Turnip Crops. 



Avill lay about 400 eggs, which would be transformed in a few weeks 

 to 400 moths : if we allow half of these to be females, they would 

 lay at the same rate 80^000 eggSj which would in the following 

 autumn (admitting that the first was a vernal moth) become per- 

 fect insects^ whose eggs, taking again half of them as females, 

 would amount to the prodigious number of 16,000,000, which 

 would hatch the following spring, and be ready to devastate the 

 spot on which they were bred : there must be, consequently, in- 

 numerable agents in operation to stop their increase, although I 

 do not happen to have met with the species of ichneumons, «Scc. 

 which are destined to preserve our green crops from being anni- 

 hilated by the caterpillars of the Y-moth. 



Plusia (jamma is a widely-dispersed insect, being found all 

 over Europe, and it is said to extend even to the frontiers of 

 China and Siberia : it likewise inhabits North America. Unlike 

 most other species of Noctuidse, this moth flies about by day, not 

 only in the sunshine, but regardless of the weather, it will be 

 seen on dull and even damp days hovering over flowers, and^ like 

 a sphinx-moth, thrusting in its long spiral proboscis or tongue to 

 extract honey from the nectaries ; at other times, fluttering and 

 running over the flowers, or resting upon them with its wings 

 closed. There is no moth more shy and difficult to catch by day, 

 for it will seldom allow any one to come near it, but whether it 

 detects the approach of man by its eyes, which sparkle like living 

 rubies, or by its hearing, is not knovv^n : it darts off, however, in 

 an instant when disturbed, and stops again a few yards off, or 

 entirely vanishes. 



Should the Y-moth caterpillars ever become fearfully abundant 

 in our turnip-fields, it is not improbable that ducks, poultry, and 

 fcheep might be very serviceable in diminishing their numbers, if 

 employed as recommended in the last report upon the black 

 caterpillar. 



Having nov/ given an account of several kinds of insects con- 

 nected with the turnip crops, T must leave for a future opportu- 

 nity some others which are equally interesting, and not less de- 

 structive. The following summary will be useful, by placing 

 before the reader in a concise form the results of my investiga- 

 tions : — 



History of the Aphides, or Plant-Lice, 



Every crop, both in the fields and gardens, is subject to the 

 attacks of various species. 



Two different sorts infest the leaves of the English turnips, 

 one haunts the leaves of the swedes, and another the Jioiver-stalks . 



The green tops are rendered less fit for cattle when infested 



