DlA]\rOND-BACK MOTH. 193 



enormous numbers both in England and Ireland, in some 

 instances almost clearing away the attacked crop. In 1883 

 and 1884, I had observations of them as being mischievous to 

 leafage of White and Swede Turnip, Eape and Kohl Eabi, and 

 from 1884 I had no further reports of the presence of the 

 infestation until the autumn of 1889. The localities from 

 which specimens were sent were chiefly various parts of 

 Yorkshire, likewise from Aberdeenshire, and in 1889 from 

 near Henfield in Sussex. 



The attack is very widely distributed ; it is said to occur 

 over all Europe, and I have had specimens from Cape Colony. 



The caterpillars are about half an inch long, spindle- 

 shaped (that is somewhat tapering to the head and tail), and 

 sixteen-footed. Colour a delicate green, head yellow or grey 

 (or, as described by one continental observer, black), segment 

 next to the head marked with minute black dots, and the two 

 succeeding segments each marked with a small oval yellowish 

 spot on either side of the middle line. The succeeding 

 segments, as well as the first, with some minute black dots. 



As many as two hundred and forty of these caterpillars 

 have been counted on a single plant of moderate size. When 

 full-fed they spin cocoons of fine net-like texture on the 

 remains of their food-plants, or on the ground, from which 

 the moth comes out in about three weeks or less, so that 

 there may be a succession of generations during the summer. 

 The autumn chrysalids remain unchanged during the winter. 

 The caterpillars feed in heads of Cauliflower, and on unripe 

 seeds of some plants of the Cabbage kind, as well as on 

 leafage. 



In the specimens observed, the light cocoon was left open 

 at each end, so as to allow the chrysalis to leave its old cater- 

 pillar-skin outside at one extremity, and the moth on coming 

 out of the chrysalis case to escape at the other. 



The chrysalis is greyish white, with several black streaks 

 down the back and sides. The moth, which soon hatches (in 

 the summer), to the naked eye appears not unlike the Clothes 

 Moth. When magnified it will be seen (as figured at p. 192) 

 that the fore wings are long and narrow, greyish-brown, darker 

 towards the centre, with a rather broad whitish band along 

 the wing towards the hinder margin, this stripe being waved 

 so that when the moth is at rest the two edges of the wings 

 laid flat along the back form a row of pale diamond-shaped 

 markings, whence the name of " Diamond-back Moth." The 

 hinder wings are narrow, of a pale ashy grey colour, and have 

 a long fringe. The spread of the wings is about two thirds of 

 an inch. There appears to be a succession of broods, as the 

 moth is observable from the end of June until October. 







