18 Journal New York Entomological Society. [Voi. iv. 



to the sudden slipping off of the base of the wing-cover from the base 

 of the wing. This arrangement is highly developed in the genus Cir- 

 cotettix, whose members are noted for the clacking noise produced in 

 flight, which it seems to me may perhaps be thus produced by the sud- 

 den, and more or less rapidly repeated, opening and closing of the 

 flight- organs. 



There is another group of locusts found with us, fewer in species, 

 smaller in size, and of less conspicuous habits, but more plentiful in 

 numbers than the Qildipodinse, which stridulate not during flight, but 

 when at rest, — these are the little oblique-faced Tryxalinee. In this 

 group the sound is produced by rubbing the hind thighs against the 

 wing-covers, and both the apparatus and its working are readily ob- 

 served. It consists, in most of our species, of a row of fine teeth pro- 

 jecting from the inner side of the hind thighs of the male in such a 

 position as to engage the elevated veins of the basal part of the wing- 

 covers, by this means setting up vibrations in the latter. This may be 

 readily demonstrated in the fresh insect or a relaxed specimen. The 

 sounds produced in this way are entirely different in character from 

 those made by the QEdipodinse in flight, being a scraping or scratching, 

 as distinguished from a rattling, crackling, or rustling. 



There is, however, a genus (^Mecostethiis) of this group which is 

 allied to the (Edipodinje in structure, and the males of one of its species 

 produce the loudest note made by any of our Tryxalinae. In this genus 

 the hind thighs of the males are destitute of teeth, which are borne in- 

 stead upon a supernumerary vein of the wing-covers, which is raised 

 above the others. In the species referred to the teeth on this vein are 

 high and very acutely pointed. 



This additional vein is found in all our representatives of the 

 CEdipodinae, which stridulate in flight, and the discovery of this ar- 

 rangement of the apparatus in Mecostethus led me to examine this vein 

 in several species of Qidipodin^e to see whether it was ever supplied 

 with a rasping surface ; for if so, these locusts also could doubtless 

 stridulate when at rest. It was found in several species to be provided 

 with teeth of different degrees of effectiveness, and not long afterward I 

 was enabled to witness the use of this form of stridulating apparatus by 

 an CEdipodine. 



While walking up the Mt. Washington carriage-road one bright 

 morning in early September I came upon a group of several males of 

 Circotettix verruculatas sunning themselves by the roadside in the 

 shelter of an overhanging cliff. The night had been quite cool and 



