NO. 1310. NORTH AMERICAN THYSANOPTERA-HINDS. 91 



are not normally laid back along the body when at rest. In the 

 Terebrantia the first two segments are usually markedly broader than 

 the others. 



Larval antennae vary considerably from those of adults. The num- 

 ber of segments is constantly smaller, and the form is generally 

 changed. Sense cones are not present, and the arrangement of spines 

 is quite different from that in the adult. 



ORGANS OF VISION. 



Eyes.— KAwXt Thrips possess faceted eyes, which are borne upon 

 the front angles of the head and extend downward onto the frons 

 about as far as they do upward onto the vertex; rarely they are situ- 

 ated farther back upon the sides of the head, but stilf near the front. 

 They are circular, oval, or reniform in outline. The size and number 

 of facets varies consideral)ly in different species, as does also the close- 

 ness of the facets to each other. The eyes are quite large, as com- 

 pared with the size of the head, being together about one-half the 

 width of the head through them. In many species, especially in Tere- 

 brantia, they are strongly protruding {fldiothrlj)^, PaHh^nothrlpd). 

 The individual facets are usually considerably swollen, and small hairs 

 project from l)etween them, thus giving the eye a peculiar resem- 

 blance to the surface of a raspberry. The cornea is quite thick, trans- 

 parent, usually slightly tinged with yellow, and appears like a light- 

 colored margin around the outside of the eye. The part of the head 

 closely adjoining the eye is frequently also much lighter in color than 

 the remainder of the head. 



The pigmentation of the eye is dense and dark, so that, as a rule, 

 by transmitted light the eye is entirely opaque, while by reflected 

 light it may be red or very dark purple in color. 



The eyes of larvffi are much smaller and simpler than those of the 

 adults. They consist of but few large, separated facets, and are situ 

 ated farther back upon the sides of the head. 



6>c^//*.— These are adult structures, and are not present in larv«, 

 though the pigment of the developing ocelli can sometimes be seen 

 late in the larval stage. They are not always present, however, even 

 in the adults. They are three in number, situated more or less closely 

 together between the eyes on the vertex of the head, and are placed 

 always in the form of a triangle, with its apex forward. Rarely only 

 two ocelli are present, and it is then the front one which is wanting. 

 Ocelli are present in all winged forms, and usually also in the short- 

 winged forms of winged species. They are absent, however, in 

 entirel}^ wingless species. 



MOUTH PARTS. 



The mouth parts of Thiips are difiicult to study, and so peculiarly 

 modified that it has been found hard to determine their homoloo-ies. 



