440 Mr. Charles J. Giahan on 



that the stridulating area in these insects is situated on 

 the underside of the head. 



In S. destructor, ratzehurgi, primi and midtistriatus, it is 

 a narrow elongated, very slightly elevated space, running 

 along the middle, up to the hind margin of the head, and 

 crossed by a series of very fine parallel ridges, the shape of 

 the area being almost exactly the same in all of these 

 species (PI. VII, figs. 9 and Oa). 



In >S^. intricatus the stridulating area is shorter and 

 broader, and appeared to me (but of this I cannot speak 

 with certainty, not having made exact measurements) to 

 be somewhat less finely striated (PI. VII, figs. 10 and lOrt). 

 Scoli/tus ruf/ulosus appears to be without a true stridu- 

 lating area, the gula in this species being marked along 

 the middle with a depressed line or groove from which 

 coarse ridges run transversely towards the sides of the 

 head. Ridges of a similar character, often continued right 

 across the underside, and sometimes all round the head, 

 are met with in other Scolytichv, and occur frequently 

 among the Ctirculionidx. They are in some cases so 

 regular and parallel as to make it doubtful whether they 

 do not serve for stridulation, but certain species in which 

 they occur are not known to stridulate, and as I have 

 found them present in species which possess a true stridu- 

 lating area on the elytra, I am inclined to think they are 

 never used for that purpose. 



Stridulating organs situated on the mandibles and 

 maxillse have been described by Schiodte as occurring in 

 the larva3 of certain genera of Di/nastid/e, Cctoniidx., 

 RutclidiV, SericidcV, Mdolonthidiv and Coprid/v. They con- 

 sist of (1) a series of teeth on the upper face of the 

 maxillary stem (stipes), and (2) special granulations vari- 

 ously placed and grouped on the lower face of the mandi- 

 bles, the parts being so disposed that the teeth on the 

 maxilla3 reach and rasp the granulations on the mandibles 

 Avhen the maxillse are moved backwards and forwards. 

 In Dijnastidiv and Cctoniidiv the granulations are arranged 

 to form rather strong transverse ridges, which occupy a 

 somewhat elliptical and completely circumscribed area 

 near the base of each mandible. In the Butclidm they 

 differ only in that the ridges formed by them are much 

 finer, more numerous, and placed closer together ; but in 

 the larvse of the other groups the granulations do not form 

 ridges. Dr. Sharp believes that these structures are little 



