182 



THE SCOLYTID BEETLES. 



from five to eight spiracles fall into the following subfamilies as recog- 

 nized by the writer: ^ 



Table IV. — Abdominal spiracles in the subfamilies of Scolytoidea in ivhich species vjere 

 examined by Niisslin and Fuchs. 



Subfamily . 



Eight 

 spiracles. tt 



Seven 

 spiracles. 



Six 

 spiracles. 



Five 

 spiracles. 



Cryphalinse 



Genera. 



Genera. 

 2 

 1 



Genera. 

 3 



Genera. 



2 









Corthylinse 





1 





Micracinse 







2 





1 



2 



1 

 8 

 1 



i' 



2 



1 





4 



Hylesininse . . 



1 



3 

















Total 



2 



15 



7 



12 







a The eighth spiracle is rudimentary. 



In the genus Hylesinus (Fuchs, ibid., p. 13) there are from five to 

 seven spiracles with the sixth and seventh rudimentary, while in 

 Dendroctonus and Tlylurgoys the eighth is rudimentary. Doubtless 

 if the number of abdominal spiracles were determined for all of the 

 species, some good evidence would be furnished as to fines of modi- 

 fication. 



ABDOMINAL STERNITES. 



The abdominal sternites 1 and 2 are fused and concealed in the 

 coxal cavity, 3 to 7 are exposed, and the eighth is covered by the 

 seventh, while the ninth and tenth evidently are represented by the 

 genital organs. (See Pt. I, pp. 25 and 38, and Technical Series 20, Pt. 

 I, Pis. VII, VIII, and IX, as also the discussion of the reproductive 

 organs in the present paper.) The exposed sternites are quite vari- 

 able in the different genera and species, and certain characters are of 

 value in designating minor groups of genera, but few, if any, are com- 

 mon or pecufiar to a subfamily. 



The modifications range from the simple type found in the Crypha- 

 linse to the steep, excavated, armed, and odd forms of the Scolytidse 

 and Platypodidse. There is a wide variation, which is apparently 

 of specific importance, in the eighth ventral segment. The palpi of 

 the ninth ventral segment (Niisslin, Fuchs, and others) found in the 

 females of Scolytus and Hijlesinus, may after all represent the tenth 

 tergite or sternite, one or both of which may be represented by the 

 ovipositor as in certain Curcufionoidea (Pissodes) , Cerambycoidea 

 {OijUene), and many other insects. But this is a matter requiring 

 more comprehensive investigation. 



STRIDULATING ACCESSORIES. 



The stridulating accessories have not been investigated by the 

 writer in many genera but they appear to be confined largely to the 

 seventh abdominal tergite and the inner subapical area of the elytra 



