ANATOMY AND PHYSIOLOGY 83 



folds (Passalus cornn(ns), not to mention other methods. In most cases 

 one part forms a rasp and the other a scraper, for the production of sound. 



In many of these instances the sound serves to bring the two sexes 

 together and is not necessarily confined to one sex; thus in Passalus cor- 

 nutus both sexes stridulate. 



A few moths (Sphingidae) and a few butterflies make sounds; the South 

 American butterfly Ageronia feronia emits a sharp crackling noise as it 

 flies. A rasp and a scraper have been found in several ants, though ants 

 very seldom make any sounds that can be distinguished by the human 

 ear; Mutilla. however, makes a distinct squeaking sound by means of a 

 stridulating organ similar to those of ants. 



Stridulating organs attain their best development in Orthoptera, in 

 which group the ability to stridulate is often restricted to the male, though 

 not so often as is commonly supposed. Among Acridiida?, Stenobothrus 

 rubs the hind femora against the tegmina to make a sound, the femur 

 bearing a series of teeth, which scrape across the elevated veins of the 

 wing-cover; while the male of Dissosteira makes a crackling sound during 

 flight or while poising, by means of friction between the front and hind 

 wings, where the two overlap. 



Locustidae and Gryllidas stridulate by rubbing the bases of the teg- 

 mina against each other. Thus in the male Microcentrum laurifolium the 

 left tegmen, which overlaps the right, bears a file-like organ of about fifty- 

 five teeth (Fig. 136), while the opposite tegmen bears a scraper, at right 

 angles to the file. The tegmina are first spread a little; then, as they close 

 gradually, the scraper clicks across the teeth, making from twenty to 

 thirty sharp ''tic 1 ' -like sounds in rapid succession. This call guides the 

 female to the male and when they are a few inches apart she makes now 

 and then a short, soft chirp, to which he responds with a similar chirp, 

 which is quite unlike the first call and, moreover, is made by the opening 

 of the tegmina. These and other details of the courtship may readily be 

 observed in twilight and even under artificial light, as the latter, if not 

 too strong, does not disturb the pair. Something similar may be ob- 

 served in the daytime in Orchelimum, Xiphidium and the tree crickets, 

 (Ecanthus. The stridulating areas are usually membranous and the rasp- 

 ing organs are modified veins. Frequently the wing-covers bulge out to 

 form a resonant chamber 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, Orchelimum vul- 



