NO. 1310. NORTH AMERICAN THYSANOPTERA— HINDS. 89 



In nearly all species numerous short, small s})ines are borne upon 

 the various parts, especially upon th<^ prothorax, legs, and antennie. 

 Larger and more conspicuous spines or bristles mark especially the 

 exposed parts of the })ody such as th(> vertex of the head, the angles 

 of the prothorax, the veins of the wings in the Terebrantia, and the 

 last two or three segments of the alidomen. Special modifications of 

 thes(^ larger spines are found in many adult Tu1)ulifera in the form of 

 hairs which have usually a slender shaft and at the tip are roundly 

 knobt)cd or irregularly funnel-shaped, though sometimes they are 

 short and cut otf squarely at the tip where they ar(> fully as large as at 

 their base. 



Larva^ and pupa? of both suborders, in many cases, bear such 

 knob])ed or funnel hairs which, when present in the pupte, are even 

 longer and more slender than in the larva*. The spines in manj' cases 

 are placed in quite regular segmental rows, both in transverse and 

 longitudinal directions. 



HEAD. 



The form of the head is peculiar and extremely variable. (See figs. 4, 

 14, 27, 55, 1*3, 107, etc.) But while this variation is great between 

 difi'erent species, the proportion of length to breadth in the same 

 species is very constant. The different sclerites forming the head are 

 so completeh" fused as to be indistinguishable and we can therefore 

 designate the regions of the head only in a general ^\^y. The dorsal 

 portion back of the eyes is called the occiput, that between the eyes 

 and extending forward to the bases of the antennae is the vertex, 

 between the bases of the antennas and the attachment of the mouth 

 cone on the ventral side is the frons, while the sides of the head are 

 called the cheeks (gense of other orders). The usual appendages of 

 the insect head are present and will be considered separatelv. 



Antennte. — These are inserted upon the extreme front of the lunid 

 and stand quite closelv together upon the front margin between the 

 eyes. They are always much longer than the head and may be two or 

 three times as long. The number of segments is a character of much 

 importance in classification and varies from six to nine. The form of 

 the segments ranges from cylindrical to almost spherical, and this 

 character is also of importance in classification. The spines upon the 

 segments become more numerous as the apex is approached, and on 

 the intermediate segments are mostly borne upon the apical half of 

 each. The ^IColothripidjB lack the specialized form and arrangement 

 of the spines which is found in Thripidse; their antennre are quite 

 uniformly clothed with short hairs or bristles. In the Thripida? this 

 general hairiness is lost, except in those species having whorls of hairs 

 around intermediate segments, while a few^ much longer and usuall}^ 

 more conspicuous spines are developed. The antenna! spines of Phloe- 

 othripidai resemble in a general way those of Thripidie. In both 



