170 LIFE-HISTORY OF THE DIAMOND-BACK MOTH. 
Having selected a part for examination, I followed up the rows, 
examining each plant as it came, and thus I looked over some 
hundreds of plants in each field. While thus occupied I was 
startled over and over again by something like a tiny bit of stick 
jumping out of the leaf, passing before me like a minute flash of 
light, and immediately being lost in the soil below ; of these I took 
no notice, feeling sure in my self-confidence that the object of my 
pursuit was a moth of some proportions. By the third day, not 
having met with my ideal, I brought my mind down to these tiny 
creatures ; so having watched their peculiar mode of movement, I 
was soon able to capture one, and on examining it with a lens was 
enabled, to my great joy, to recognise the diamond forms on its 
back, which at once assured me I had found the cause of the 
mischief around. 
From the large amount of destruction caused by these insects, 
the turnip leaves being destroyed by the acre, I very naturally 
supposed the caterpillar would have been of considerable size and 
easily found, either having long brown hair, or brilliantly striped 
with yellow or green, or some such distinguishing feature; but now 
having found a tiny moth, it was not long before I was enabled to 
discover a supply of the small green caterpillars as they were 
feeding, screened by the large veins of the under side of the leaves. 
The caterpillars are usually green, about half-an-inch long, with 
darker heads, and tapering at each end. (Plate VIII., Figs. 1 and 2.) 
From conversation with the residents it appeared that throughout 
this immediate district about one acre out of every three of the 
turnip crops was destroyed ; while a little to the south, nearer to 
Norwich, I found the estimate to be about one acre in five. For the 
next week or two I had the opportunity of watching the habits oi 
these insects and the changes they effected in the turnip fields, and 
found the great destruction was caused by the vast numbers rather 
than the great size of the caterpillars, as from ten to thirty, or 
more, have been found feeding upon a single leaf. 
The season seemed to have been peculiarly favourable to their 
development, and about midsummer their increase appeared pro¬ 
digious, and perhaps during the first fortnight in July the larger 
August, 1893. 
