THE DIAMOND -BACK MOTH. 257 



keepers would conclusively prove (?) — the query is mine — that 

 there had been a large importation of these moths from abroad, 

 as in most cases the outbreak of the caterpillar occurred soon 

 after that date." 



Not only, however, has this insect-pest been conspicuous for 

 its abundance on this side of the globe, but, according to ' The 

 Cheshire Observer' for Oct. 10th, it "has also done an immense 

 amount of harm this year to the turnip crops in New Zealand and 

 Tasmania." The migratory, or blown-over, theory must there- 

 fore credit this insect-speck with an organisation which enables 

 it to continue on the wing for 400 or even 1000 miles, or to sail 

 such distances on the wings of the wind. 



Leaving this problematic part of the subject, let me say I 

 obtained almost full-fed larvae of P. cruciferarum from North- 

 umberland, Durham, and Yorkshire in the first week of August. 

 With Lincolnshire I was unsuccessful, as my correspondent there 

 happened to be from home, and the larvae had disappeared before 

 his return. 



Some of the readers of the ' Entomologist ' may be interested 

 to know that the caterpillar — dorsally and underneath, legs and 

 claspers — is pea-green. In some specimens there were indi- 

 cations of a dorsal, and on each side a subdorsal, stripe of a 

 deeper green. The head is pale green, faintly tinted with purple, 

 and ornamented with minute black spots. This description also 

 applies to the second segment. Each segment has a couple of 

 rings of minute tubercles, and each tubercle emits a short black 

 hair or bristle. The anal claspers are considerably porrected, 

 or stretched out behind, and they give a very bifurcated appear- 

 ance to the termination of the caterpillar. Such is the aspect 

 under a strong magnifying-glass. To the unassisted eye it is 

 simply a short green caterpillar, five-twelfths (nearly half an inch) 

 long, and tapering at both ends. It feeds on turnips, cabbages, 

 cauliflowers, and, as Stainton observes, " other Cruciferae." It 

 is very partial to the under sides of the leaves, and falls off the 

 food-plant on being disturbed, or wriggles about and away, either 

 head or tail first, after the manner of Tortrix larvae. When 

 shaken off its food-plant it generally suspends itself by a silken 

 thread, by means of which it can speedily return. 



My caterpillars began to pupate on the 11th of August. At 

 first the chrysalis is pale green, but changes in a few hours to 

 light grey, with smoke-coloured streaks, visible to the naked eye. 

 The pupa is a quarter of an inch long, and can be easily seen 

 through the spindle-shaped cocoon of open network, which is 

 fastened either to the upper or under side of a leaf. The cater- 

 pillars showed a marked preference, in spinning up, for the gauze 

 covering of the flower-pot. Under a good magnifying-glass the 

 cocoon appears to be made of whitish silken ropes, arranged in 

 irregular meshes across the chrysalis, which, with its smoky 

 markings, is very distinctly seen. 



