14 BULLETIN 902, U. g. DEPARTMENT OF AGRICULTURE. 



proved. The larva spins a light gray cocoon in which it transforms 

 to pupa, and the adult parasite emerges through a small hole which 

 it eats out of the end of the cocoon. The greatest percentage of 

 parasitized beetles observed at any one time was 1 6. 



Just what influence this parasite has in holding the beetles in 

 check has not been determined. It is sometimes an important 

 enemy of the related striped cabbage flea-beetle (PhyMotreta vittata 

 Fab.) 



A NEMATODE PARASITE. 



Nematodes infest the adult beetles; As generally observed these 

 nematodes were young and small, about 1/40 cf an inch in length. 

 From 200 to 500 were counted in a single beetle. In several instances 

 adult female nematodes were observed which had the body sack filled 

 with newly developed nematode young that had not yet escaped. 



As nearly as could be determined the nematodes were not confined 

 to the digestive tract but appeared to be in the body cavity. In a 

 number of cases eggs laid by the beetles were found to be infested 

 externally with the nematodes. The eggs had an unhealthy ap- 

 pearance and in no instance were infested eggs observed to hatch. 

 Just what effect the nematodes have on the beetles would be an 

 interesting problem to work out. 



A GREGARINE PARASITE (GREGARINA). 



Gregarine worms 9 occur in the intestines of the adult beetles, 

 infestation averaging as high as 40 to 50 per cent, but it could not be 

 determined whether these had any detrimental effect upon the host. 

 They occur in almost all forms of insects and as far as known have no 

 serious effect on them. 



BIRD ENEMIES. 



Mr. W. L. McAtee of the Biological Survey reports having found 

 the western cabbage flea-beetle in the stomachs of three species of 

 birds, and other beetles of the same genus in the stomachs of 12 kinds 

 of birds. The land birds include among enemies of these beetles the 

 common and Texas nighthawks (Chordeiles virginianus and C. 

 acutipennis texensis), white-throated swift (Aeronautes melanoleucus) , 

 horned lark (Otocoris alpestris), starling (Sturnus vulgaris), song 

 sparrow ( Melospiza melodia) , chipping sparrow (Spizdla passerina), 

 tree swallow (hidoprocne bicolor) , and marsh wren ( Telmatodytes 

 palustris) . 



CONTROL MEASURES. 



EXPERIMENTS WITH INSECTICDDES AND DETERRENTS. 



Ten experiments with arsenicals and one with nicotine sulphate 

 were made in Otero County, Colo., by the junior author, and may be 

 summarized as follows: 



8 Identified by the junior author. 



