18 
Journal New York Entomological Society. 
[Vol. 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 GEdipodinae, which stridulate not during flight, but 
when at rest,—these are the little oblique-faced Tryxalinae. 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 GEdipodinae in flight, being a scraping or scratching, 
as distinguished from a rattling, crackling, or rustling. 
There is, however, a genus ( Mecostethus ) of this group which is 
allied to the GEdipodinae 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 GEdipodinae 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 verruculatus sunning themselves by the roadside in the 
shelter of an overhanging cliff. The night had been quite cool and 
