40 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 39 



Anoplura 



Sucking Lice 



Somewhat flattened, wing- 

 less insects with essentially 

 the same habits as those of 

 the above order except that with their mouth- 

 parts, fitted for sucking, they suck blood from 

 their animal hosts. Characteristic of this order 

 are the stout claws at the 

 end of the legs of the 

 horse louse, Haematopi- 

 nus asini Linnaeus, shown 

 in fig. 37. 



Fig. 37. — Anoplura. 

 Haematopinus asini, the 

 blood-sucking horse 

 louse. Actual length 0.1 

 inch. 



Thysanoptera 



Thrips 



Small, active insects, usually about one- 

 eighth inch long, rarely a quarter inch long, 

 very slender, usually with two pairs of very 

 slender wings and with the underneath side of the head forming 

 a sharp, conelike, sucking structure. The wings have a long 

 fringe on the hind margin and the front wings may 

 have one or two veins running the length of the 

 wing. The young of these insects are 

 somewhat similar to the adults but 

 are softer bodied. Fig. 38 shows an 

 adult of Thrips tabaci Lindeman, the 

 onion thrips. Thrips suck the juice 

 from plants. They are seldom noticed 

 because of their minute size, but they 

 can be collected in large numbers 

 from blossoms of almost any plant. 

 A few of them, such as the onion 

 thrips and privet thrips, attack agri- 

 cultural or horticultural plants and inflict considerable damage. 

 A few species of thrips occasionally bite human beings. 



^^ 



Fig. 38.— 

 Thysanoptera. 

 Thrips tabaci, 

 onion thrips. 

 Actual length 

 less than 0.1 

 inch. 



Corrodentia Small, rounded or flattened insects, rarely a 



Booklice, quarter inch long, usually about an eighth 



Barklice inch. Many species have two pairs of wings 



which have only a few zigzagging veins. 



They eat fungus growth on bark, dead leaves, moldy grain, 



damp books, and other materials. Winged forms such as Psocus 



striatus Walker, fig. 39, are found under bark and on dead leaves. 



Common species found in houses and on stored grain are usually 



wingless and louselike, similar in general appearance to fig. 36. 



