ANATOMY OF THE WESTERN CRICKET. 
173 
than those of the metathorax, or third thoracic segment. The ventral 
piece (sternum) is crescent-shaped, while that of the metathorax is twice 
as large and transversely ovate. 
The third segment (meta-thorax) is of the same size as the middle ring, 
but is slightly swollen on the sides, and a slightly marked, indefinite 
swelling above represents the scutellum. The flanks are larger, as they 
afford insertions for the muscles of the much larger hind legs. Both of 
the hinder thoracic segments have broad, flattened, spine-like expansions 
of the sternum; and on each side of the prothorax is a sharp slender 
spine. The third pair of legs are twice as large as the second. 
The breathing holes or spiracles by which the air enters the air-tubes 
within the body, for no insects breathe through their mouths as in the 
higher (vertebrate) animals, are eighteen in number, there being nine 
pairs. The first pair forms a large slit-like opening situated on each 
side of the prothorax, and concealed by the tergum or dorsal piece. The 
second pair are on the sides of the meso-thorax, and are of the same 
size as the eight abdominal pairs which are situated on the eight basal 
abdominal segment. 
The wings are concealed by the prothorax ; the fore pair are small and 
rounded, as broad as long ; they are considerably larger in the male 
than in the other sex. The hinder pair are minute, rudimentary, rolled 
up, and flattened down upon the body, but when opened are seen to be 
oval in form. The wings of the female are smaller than those of the 
male; they are flattened, with the veins not strongly marked, and with 
no means for producing sounds. On the contrary, those of the male are 
much larger ; the veins are raised and strongly marked, with the costal 
region, which is full and large, bent down ; the subcostal and median 
veins are large and distinct, while there is a clear oval space between 
the median and outer branch of the submedian. Below and nearer the 
outer edge of the wing is a second large sub triangular, clear, resonant 
space. The main submedian vein is large and much thickened, with a 
row of dense, fine teeth along the middle. This forms the " file" which 
rubs against the other wing. The sound may be produced in an alco- 
holic specimen by rubbing one wing upon the other. The "file" pro- 
duces the sound, the vibrations being rendered audible by the resonant, 
tense, elastic, clear spaces in the other wing, which throw a mass of 
air into pulsations. Thus the file may be compared to a violin bow, the 
veins of the wing to the strings of the violin, and the resonant surfaces 
to the box of the violin, or the elastic wing may be compared to the 
sounding-board of a piano. Not only does one fore wing rub upon the 
other, the rasping noise being produced by partially opening and clos- 
ing the wing, but it seems probable that the file rubs over the stiff? 
horny, upcurved hinder edge of the meso-thoracic segment. At any 
rate the mechanism in the fore Avings is ampjy sufficient to produce the 
sounds referred to by Mr. Thomas in his notes, wherein he states that 
" the males utter a sharp sound, not much like that of the katydid-like 
