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JOlMAlOFAGMCETIIALlSEARCa 



Vol. X Washington, D. C, July 2, 191 7 No. i 



LIFE HISTORY OF PLUTELLA MACULIPENNIS, THE 

 DIAMOND-BACK MOTH 



By H. O. Marsh, 

 Scientific Assistant, Truck Crop and Stored Product Insect Investigations, Bureau of 

 Entomology, United States Department of Agriculture 



INTRODUCTION 



In the Arkansas Valley of Colorado cabbage is grown on a moderate 

 scale, chiefly for local consumption. As is usual with this crop, it is the 

 host of numerous insect enemies, among which is the larva of the diamond- 

 back moth (Plutella maculipennis Curtis^). 



The writer has had the diamond-back moth under observation since 

 1908, and particularly since 191 4. Throughout this period, except from 

 the latter part of December, 1914, until early in March, 1915, when work 

 was carried on at Phoenix, Ariz., all life-history observations were made 

 at Rocky Ford, Colo. 



DESCRIPTION OF THE DIAMOND-BACK MOTH 



THE MOTH 



The adult (PI. i, .4) is a slender moth, grayish or brownish in general 

 color, with ocherous markings on head, thorax, and wings. The female 

 is usually lighter in color than the male. The wing expanse is about 

 five-eighths of an inch, and, when at rest, the wings are folded close to 

 the body. Flight is rather feeble and cautious, the moth usually coming 

 to rest among the leaves of cruciferous vegetables or about cruciferous 

 weeds. The nectar of such plants is the natural food of the adults, 

 although in captivity they feed readily on diluted honey. 



THE EGG 



The ^gg is minute, scalelike, greenish white or yellowish in color, 

 and is deposited singly, or rarely in groups of two or three, on the lower 

 side of the leaves of cruciferous plants. In cool weather eggs of the first 

 and last broods may be deposited on the upper side of the leaves, but this 

 is apparently abnormal. 



' Order Lepidoptera, family Yponomeutidae. 



Journal of Agricultural Research, Vol. X, No. i 



Washington, D. C. July 2, 1917 



im Key No. K— 53 



(I) 



