68 EN TOMOLOGY 
Orthoptera (to which order Gicanthus belongs). In Collem- 
bola, the embryo has paired abdominal limbs, and those of the 
first abdominal segment eventually unite to form the peculiar 
eee ; ventral tube (Fig. 12) 
of these insects, while 
those of the fourth see- 
ment form the character- 
istic leaping organ, or 
furcula. 
Cerci.—In many of the 
more generalized insects, 
Abdomen of female beetle, Cerambyx, in 
which the last three segments are used as an the abdomen bears at its 
ovipositor.—After Nope. 
extremity two or three 
appendages termed cerci. These occur in both sexes and are 
frequently long’ and multiarticulate, as in Thysanura (Figs. 
76,9, 10) and Ephemerida (Figs. 19, 8; 84),though shorter in 
cockroaches and reduced to a single sclerite in Acridiude (Fig. 
87). The paired cerci, or cercopoda of Packard, are usually 
though not always associated with the tenth abdominal seg- 
ment and are homologous with legs, as Ayers has found in 
CEcanthus and Wheeler in Xiphiduin. As to their function, 
the cerci of Thysanura are tac- 
Fic. 78. 
tile, and those of the cockroach — 
olfactory, while the cerci of 
male Acridiidz often serve to 
hold the female during copu- Abdomen of a female midge, Cecido- 
myia leguminicola, to show the pseudo- 
lation. 
Extremity of Abdomen.— 
Various modifications of the terminal segments of the abdo- 
ovipositor. 
men occur for the purposes of defecation and especially repro- 
duction. The anus, dorsal in position, opens always through 
the last segment and is often shielded above by a suranal plate 
and on each side by a lateral plate. The genital orifice is al- 
ways ventral in position and occurs commonly on the ninth 
abdominal segment, though there is some variation in this re- 
spect. ‘The external, or accessory, organs of reproduction are 
termed the genitalia. 
