IO6 ENTOMOLOGY 



Frequently the wing-covers bulge out to form a resonant cham- 

 ber that reinforces the sound. 



The naturalist can recognize many a species of grasshopper 

 by its song; Scudder has expressed some of these songs in 

 musical notation. The usual song of the common meadow- 

 grasshopper, Orchcliinum vulgar c, may be represented by a 

 prolonged sr . . . sound, followed by a staccato jip-jip-jip- 

 jip. . . . 



In Orthoptera, the frequency of stridulation increases with 

 the temperature; and the correlation between the two is so 

 close that it is easy to compute the temperature from the num- 

 ber of calls per minute, by means of formulae. The formula 

 for a common cricket [probably a species of Gryllus] ; as given 

 by Professor Dolbear, is 



r. ,. + = 



Here T stands for temperature and N, the rate per minute. 



A similar formula for the katydid (Cyrtophyllns pcrspicil- 

 latus) , based upon observations made by R. Hayward, would 

 be 



Here, in computing N, either the " katy-did " or the " she- 

 did " is taken as a single call. 



Hearing. There is no doubt that insects can hear. The 

 presence of sound-making organs is strong presumptive evi- 

 dence that the sense of hearing is present. Female grass- 

 hoppers and beetles make locomotor and other responses to 

 the sounds of the males, and male grasshoppers will answer 

 the counterfeit chirping made with a quill and a file. 



Auditory organs are not restricted to any one region of an 

 insect, but occur, according to the species, on antennas, abdo- 

 men, legs or elsewhere. 



The antennae of some insects are evidently stimulated by 

 certain notes, particularly those made by their own kind. 

 Thus the antennae of the male mosquito are auditory, as 



