336 XEW YORK STATE MUSEUM 



injurious on account of its malting' small black walled r^ralleries which 

 matcriall}' lowt-r thr market value- of infested lumber. 



CERTAIN .STltUCTURKS OF srOLYTIDS 



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 

 tile 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 

 engageci 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 [jlate 67, figure i, showing the single jointed funicle of 

 Monarthrum mali Fitch, \niique in this extremely interesting group. 

 The strongly flattened and enormously dilated club or terminal segment of 

 C h r a m e s u s h i c o r i a e Lee. is extremely characteristic. The two 

 antennae of Scohtus, S. rugulosus Ratz. and S. qu ad r i s p i n o s u s 

 Say [pi. 67, fig. 10 and 15J 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. I and 3 respective!)! are very different from those of other scolytids. 

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

 species of Toniicus, 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 1 appears to be very characteristic of this genus. 



The tibiae of various species also present characters whicli 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 ot the minor 

 chitinous tul)ercles or processes. The closely allied species of Dryocoetes, 

 D. eichhoffii Hopk. and D. autographus Ratz. vary sufhciently, 

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

 hicoriae Lee. 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 Xyloclepteo 

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



