MORSE: ORTHOPTERA OF NEW EXGLAND. 
225 
projecting or dove-tailed between the lateral portions of the 
metasternuni. 
The terguni is rigidly joined to the metanotuin. On each side, 
near the lower end, is a large crescentic opening lined at the 
bottom by a delicate whitish membrane, the tijmpanuyn, which is 
beheved to be part of an organ capable of perceiving sounds. 
Near its front margin maj' be seen a tiny opening, the spiracle of 
the first abdominal segment. Other spiracles may be seen near 
the lower margins of the terga of the second to eighth segments 
inclusive. 
supra-anal plate 
10 
supra-anal plate 
10 cercus 
tympanum 
spiracle 
Female 
ovipositor 
podical plate 
Abdomen 
subgenital 
plate 
Male 
I'p 17 
FiQ. 16. — Side view of abdomen of female Locust. Enlarged. (Original.) 
¥iQ, 17. — Side view of end of abdomen of male Locust. Enlarged. (Original.) 
The apical portion of the abdomen differs characteristically 
according to the sex. If a sufficient number of examples be 
examined, some will be found (the larger ones) in which it ends 
in four sharp, slightly recurved horny points, two dorsal, two ven- 
tral, — the upper and lower blades or valves of the ovipositor of 
the female. The exact shape of these valves varies specifically 
and is frequently useful in diagnosis. They may be found lying 
very closely together, the abdomen tapering to a point; or the 
tips of the dorsal maj- be widely separated from those of the 
ventral pair, even to an angle of 150°. In egg-laying, the tips 
are repeatedly forced into the ground and spread apart, opening a 
cavity to a depth sometimes considerably exceeding the usual 
length of the abdomen. In this cavity the eggs are deposited. 
By this means the Sprinkled Locust customarily excavates its 
egg-cavities even in wood, usually soft pine it is true, or that 
which is partially decayed. 
The sternum of the ninth segment is considerably longer than 
its corresponding tergum, and is the last ventral segment visible 
