July 2, 1917 Life History of Pluiella maculipennis 



February, 1915. In August, 1916, larvae were noted on cabbage and 

 turnip at Maxwell and French, N. Mex. 



FOOD PLANTS 



The larva of the diamond-back moth appears to feed exclusively on 

 cruciferous plants. The writer has observed it feeding on the following 

 cultivated varieties: Cabbage, cauliflower {Brassica oleracea botrytis), 

 turnip, radish (Raphanus saiivus), rape (Brassica napus), kale (Brassica 

 oleracea ace phala), mustard (Brassica nigra) , " Chinese mustard " (Brassica 

 juncea), kohlrabi (Brassica oleracea caulo-rapa), watercress (Radicula 

 sinuata), horse-radish (Radicula armoracea), sweet alyssum (Koniga 

 niaritima), and candytuft (Iheris amara). While cabbage is decidedly 

 the favorite, rape, cauliflower, turnip, and mustard are readily eaten. 



Among weeds the writer noted the larvae on only two species: Wild 

 watercress (Roripa sinuata) and hedge mustard (Sisymbritim sp.), both 

 being plants with mustard-Hke characteristics. Although the larvae feed on 

 the foliage of these weeds, they prefer the blossom buds or the blossoms, 

 and are much more likely to be found among these than on the leaves. The 

 watercress occurs in abundance along fences and irrigation laterals in 

 the Arkansas Valley. It blossoms from early spring until late summer 

 and supplies readily available food for the moths and larvae. The hedge 

 mustard, tentatively identified by Prof. J. J. Thornber, of the Arizona 

 Experiment Station, as Sisymbrium irio, is a common weed in the irri- 

 gated sections of southern Arizona and blossoms throughout the winter. 



SEASONAL HISTORY 



At Rocky Ford, Colo., seven generations of the diamond-back moth 

 occur annually. The winter is passed in the adult or moth stage. Moths 

 which develop during October and November find shelter throughout the 

 winter among the leaves of cabbage plants and other crop remnants left 

 standing in the field. 



In the spring following a dry "open" winter the moths are noticeably 

 less numerous than after a winter of heavy snows; hence, it would appear 

 that snow serves as an additional protection for the hibernating adults. 

 Although larvae and pupae occur in small numbers in the field during 

 November and occasionally in early December, they do not survive the 

 winter. The writer repeatedly experimented with larvae and pupae, both 

 indoors and out, to determine their resistance to cold, and in every case 

 all died during the late fall or early winter. The most painstaking 

 examination during the spring months failed to reveal a single living lar\'^a 

 or pupa on cabbage or other plants standing in the field or stored in cellars 

 or pits. 



On the other hand, the writer found living moths in the field at Rocky 

 Ford throughout the entire winter. They usually hibernate among the 

 dead or drooping leaves of cabbage plants, crawling between the leaves, 

 with the advent of the first severe frosts, where they remain concealed 



