33^ NEW YORK STATE MUSEUM 



injurious on account of its making small black walled galleries which 

 materially lower the market value of infested lumber. 



CERTAIN STRUCTURES OF SCOLYTIDS 



Scolytid beetles are so small and present such slight differences in gen- 

 eral form, that a study of minor structural details is absolutely necessary for 

 the adequate separation of species, unless we rely largely on food habits, 

 something which is not always practical. Color has very little value and as 

 a consequence we have felt obliged to give some attention to structural 

 details, in spite of the fact that a distinguished authority on this group is 

 engaged in a comprehensive study of these beetles. 



The classificatory value of the antennae has long been recognized. 

 They vary widely in character, as has been pointed out by earlier writers, 

 though to our knowledge no one has figured these organs in many of our 

 native species. The exceeding variability in structure is well illustrated 

 by reference to plate 67, figure 1, showing the single jointed funicle of 

 Monar thrum mali Fitch, unique in this extremely interesting group. 

 The strongly flattened and enormously dilated club or terminal segment of 

 Chramesus hicoriae Lec. is extremely characteristic. The two 

 antennae of Scolytus, S. rugulosus Ratz. and S. quadrispinosus 

 Say [pi. 67, fig. 10 and 15] are peculiar on account of the dark colored, 

 triangular, chitinous structure in the club. The lamellate antennae of 

 Phloeotribus liminaris Harr. and P. frontalis Oliv. [pi. 66. 

 fig. 1 and 3 respectively] are very different from those of other scolytids. 

 The disposition of the sensory areas on the expanded club of the various 

 species of Tomicus, is of considerable specific value [pi. 66, fig. 4-9 inclu- 

 sive], while the general structure of the antennae of Dendroctonus [pi. 66, 

 fig. 10] appears to be very characteristic of this genus. 



The tibiae of various species also present characters which are of con- 

 siderable value in the separation of different forms, though we should expect 

 to find more or less variation in the number and development of the minor 

 chitinous tubercles or processes. The closely allied species of Dryocoetes, 

 I), eichhoffii Hopk. and D. autograph us Ratz. vary sufficiently, 

 so that they can be recognized by this character alone. Chramesus 

 hicoriae Lec. has a very peculiar middle tibia, and the two species of 

 Scolytus are remarkable for the development of a large terminal process 

 opposite the attachment of the first tarsal segment [fig. 47]. Various specie:; 

 of Tomicus may be recognized by tibial characteristics, and Xyloclepte;; 

 possesses a very peculiar femur and tarsus. P h 1 o e o s i n u s d e n t a t u s 



