ZOOLOGICAL DEPARTMENT. 



305 



The fact that farmers are noticing these insect friends, and have now an 

 object lesson which should be rightly understood and carefully studied, leads 

 me to send out this bulletin. Ten days ago I was receiving scores of letters 

 asking about the lice; to-day I am receiving as numerous inquiries regarding 

 these friends. That instruction is opportune is evident from such questions 

 as this: "Are these insects going to complete the destruction so actively 

 begun by the lice?" 



BENEFICIAL INSECTS. 



There are two groups of these insect friends ; predaceous and parasitic 

 insects, both of which are well illustrated on the heads of wheat of our fields 

 to-day. Predaceous insects are such as devour their prey, much as the cat or 

 weasel devours the mouse. Parasitic insects are those that lay their eggs on 

 or in their victims. When these eggs hatch the larval parasite proceeds to 

 feast on its host, which thus serves it for both home and food. In the case 

 before us, as soon as the parasite has devoured the viscera of the louse, it 

 mses the skin or crust as a sort of cocoon. These gray, circular cocoons 

 (Fig. 1) are now thick among the kernels of every head of wheat, and must 

 have been noticed by every observer who has taken pains to examine. 



TJie Wheat Louse Parasite. 



This tiny black fly is by far the most important of these littls friends that 

 have come to the farmers' rescue and saved the wheat, barley and oat crops. 

 The lice that are the victims of these eager parasites are easily distin- 

 guished. They (Fig. 1) are short, rounded and gray in color. After the 

 larva disembowels the lice it uses the dry, thick skin as a 

 cocoon, in which it changes to a pupa. Very soon the 

 mature insect comes forth from a small round hole in the 

 upper, hinder part of the abdomen (Fig. 2), 

 and very soon mates and commences to lay 

 its many eggs in new victims. Of course, 

 these parasitic larvaa fairly swim in the rich 

 nutritious blood of the lice, and so are rapid- 

 ly developed . Thus we see how it is that the 

 parasites are too much for the lice. Prolific 

 as are the lice, and rapid as are they in de- 

 velopment, yet the parasites are even more so, and thus it is 

 that in ten days the parasites have so outnumbered the lice 

 that the latter have been routed and driven from the field. 

 The little flies are just about one-tenth of an inch in length. They 

 are black above and yellowish brown beneath. The antennae are black, 

 while the front, mouth parts and legs are yellowish brown. In some speci- 

 mens the femora and tarsi are dusky, and the under side of the abdomen 

 quite dark. Occasionally we find specimens with the upper part of the 

 abdomen brownish, except the pedicel and tip. There seems much variation 

 in the color of abdomen and legs, though in most cases the dorsal surface is 

 black, and the ventral surface and legs brown. The occiput or collar con- 

 necting the head and throax is brown. The antennas (Fig. 3) are sixteen 

 jointed in the female and seventeen in the male. They are cylindrical, re- 

 39 ' 



Fig. 1— Parasit- 

 ized louse. 



Fig. 2.— Parasitized 

 louse, showing exit 

 opening. 



