NOTES ON INSECTIVOROUS C0LE0PTER4 



BY S. A. FORBES. 



Mouth Structures of Carabid^e. 



In studying the food of birds, I found it necessary to 

 construct a key to the genera of the Carabida?, based pri- 

 marily upon the mouth structures, and prepared for this 

 purpose a large number of slides of the mouth parts of 

 Illinois species. In studying these, two characters were 

 noted, which proved to be of considerable service for clas- 

 sification. The first of these is the frequent obliteration 

 of the suture between the mentum and the gula (called 

 the "gular suture", b}'^ Dr. LeConte, in his Classification, 

 Pt. I., pp. X., XIII., 14, 15 and 16), the mentum being, in 

 such cases, connate with the gula. This is true of Blechrus, 

 although in Trechicus and Metabletus of the same group 

 the suture is distinct. The mentum is again connate in 

 many species, at least, of several genera of Dapti and 

 Eurytrichi ; viz., Geopinus, Anisodactylus, Xestonotus, 

 Spongopus and Amphasia ; but is not connate in Notho- 

 pus, Piosoma, Discoderesor Anisotarsus. This character 

 was noticed nowhere else except in Amara angustata^ 

 which differs in this respect from all the other Amarae in 

 the Laboratory collection. This species is also peculiar in 

 the ver}^ great development of the muscular ridges on the 

 upper surface of the mentum. In the Lebia? this mental 

 suture is distinct in the middle but obsolete at the ends- 

 The second character referred to is found in the stipes 

 of the maxilla. This body is covered with three plates — 

 an outer, closely connected with the palpus, a lower, from 

 which the two lobes of the maxilla spring, and an upper 

 plate, which is applied to the under surface of the mandi- 

 ble. The last of these usually presents, in the Harpalidaa, a 



