40 



THE SCOLYTID BEETLES. 



lobes slightly longer than jomt 4; joint 5 from tip of lobes of 3 is 

 never as long as the others (1 to 3) together, but sometimes shorter 

 than 1 and rarely equal to 2 and 3. In the males this joint is often 

 longer than in the female. 



The trochlear articulation of the tibia with the tarsus is shown in 



figure 26, in which the 

 other more important char- 

 acters are shown and 

 named. 



THE WINGS. 



Notwithstanding the vast 

 amount of pubhshed data 

 on the wings of insects,there 

 is yet much difference of 

 opinion among the leading 

 authors in regard to some 

 of the details, and much 

 confusion exists, due to 

 different interpretations of 

 the homologies of the ele- 

 ments of the wing and its 

 articulatory accessories. A 

 detailed investigation has 

 been made of the basal 

 areas of the wings of rep- 

 resentatives of different 

 orders of insects, to deter- 

 mine facts relating to the 

 fundamental plan of devel- 

 opment and modification, 

 and the system of organi- 

 zation of the elements as 

 represented in Dendroc- 

 tonus. 



Nomenclature. — Wh i 1 e 

 the more generally accepted nomenclature has been adopted, it has 

 seemed necessary to revise and more definitely define the appHcation 

 of some of the old names and to introduce some new ones to desig- 

 nate the elements heretofore obscurely defined. 



Attachments and articulations. — There are certain elements in the 

 structure, mechanism, attachments, and articulation common to 

 the wings of all insects, but within defined Hmits and according to a 

 definite system modifications, additions, and reductions occur. 

 Therefore the presence or absence of a given element should be 

 detected in any form of wing. 



Fig. 26. — Dendroctonus valens: Tibia and tarsus, articulation, 

 etc. A, Left tibia, ventral view; B, left tibia, dorsal view; 

 C, left femora, ental view; D, left tibia, dextral view of base; 

 -E, left tibia, sinistral view of base; F, tarsus; a, apical tooth; 

 6, subapical tootli; c, tarsal groove; d, subapieal ridge; e, 

 marginal teeth; /, sinistral margin; g, dextral margin; h, 

 median fossa; i, lateral condyle of tibia; J, anterior fossa; fc, 

 lateral condyle of femur; I, lateral fossa of femur; m, median 

 condyle of femur; m, attachment of extensor muscle; o, basal 

 foramen; p, attachment of flexor muscle; q, basal groove; r, 

 tibial groove. (Original.) 



