SCOLYTIDAE, 517 



2. Maxillary lobe with radiating spines on outer edge ; last joint of palpi 

 not striate ; genera, Ci-yi)turgus, Dolurgus, Stephanoderes (Hypothe- 

 nemus), Cryphalus, Mii-racis, Pityoplithorus, Dryocoetes, Tomicus, 

 Xylocleptcs. 



These characters are very difTicnlt to ol)serve and verify, and 

 after careful trial we have concluded to adhere for the illustration 

 of our fauna to the scheme proposed by Dr. Le Conte. 



Those, however, who prefer the Eiclihoffian system can make 

 the necessary changes by detaching Pityoplithorus proper from 

 Gnathotrichns, and transferring it to the Tomici; by dividing the 

 group Xylebori between Corthyli and Tomici; and by removing 

 the group Crypturgi from Hylurgini to the present tribe. 



Group 1. — Corthyli. 



In this group the species are mostly of very small size, and are 

 easily recognized by the club of the antennas, which is pubescent 

 and annulated with nearly straight sutures on both side. One 

 species of Micracis (hirtelluff) has a nearly similar club, and shows 

 thereby a resemblance to the present group, but it is otherwise so 

 closely allied to the other Micraces that it seems unnecessary to 

 separate it from them. The funicle varies from one to five joints; 

 the tibiaj are serrate or ridged transversely on the outer side; the 

 tarsi are slender, the fourth joint distinct; fifth long, with simple, 

 divergent claws. The anal segment of the % is occasionally visi- 

 ble from beneath. 



The genera may be thus separated : — 



1. Funicle 1-joijited. 2. 

 Funicle 2-5 jointed. 3. 



2. Body robust. Corthylus. 

 Body slender. Monarthrum. 



3. Outer part of funicle rather slender; 



Club of antennae fringed with long hairs. Gnathotrichus. 



Club of antennas not fringed. Pityophthorus. 



Outer part of funicle very short. Hypothenemus. 



Corthylus pnnctatissirmis depredates on maple trees in the 

 Atlantic States ; the other genera extend across the continent. 

 Hypothenemus, as understood by us, includes Stephanoderes 

 Eichhoff. 



Group II. — Xyloteri. 



The insects of this group arc rather robust and cylindrical ; 

 the declivity of the elytra is oblicpie, not excavated and not 



