EXPERIMENT STATION BULLETINS. 



245 



one and the parasite quickly goes in search of another louse. Now follows a season that 

 must be one of exquisite torture to the host animal, for the egg hatches, giving forth a 

 grub which feeds on the living body of the louse, avoiding for a time all parts that are 

 vital, but finally devouring everything. Toward the last a marked change takes place 

 in the appearance of the louse. A gradual swelling of the entire body commences and 

 this is continued until the louse becomes rotund and nearly spherical. See Fig. 12. The 

 sweAing is occasioned by the spinning of a cocoon inside the body of the louse, in which 

 the grub is to change to the pupa, and finally to the adult, winged, wasp-like insect 

 of minute proportions like its parent. When the adult is ready to emerge a round lid 

 is cut in the skin of the louse, which has turned brown, or bronzy-brown by this time, 

 and the parasite steps out eager to commence a search for more aphids. Now as each 

 parasite lays a number of eggs, the multiplication and increase of these little benefactors 

 is very rapid indeed, and when they once get a good start in a field of aphids, the doom 

 of the lice is usually sealed. The species of parasite that is here described and which 

 did such good work in Williamston, is known as Aphidius granariaphis Cook.* It is 

 one-tenth inch in length. 



Fig. 12. — Grain Aphis, rarasitized by Aphidius granariaphis. Greatly enlarged. Original. 



In the fields visited, the work of destruction went on very rapidly. In about ten days 

 after the lice became alarmingly numerous, it was necessary to search in order to find 

 good specimens and Mr. Potter tells me that the loss from the louse was not of serious 

 consequence though it looked at one time as if nothing would be left. On several occa- 

 sions severe losses have been caused by the grain louse, but in most cases the parasites 

 have checked them before any serious loss has occurred. 



Besides the Aphidius mentioned, many syrphus fly larva* were seen feeding upon the 

 lice and several adults were bred. 



Experiments have been made in New Jersey, with kerosene emulsion as a remedial 

 measure, but the feasibility of spraying a field of grain is at all times questionable, 

 except in cases where the grain is very valuable. The emulsion will kill the lice, but 



•Canadian Entomologist, Vol. XXII, July, 1890, pp. 125-6. 



