LIBRARY

48 COLLEGE ENTOMOLOGY
COLLEMBOLA and certain DIPTERA (Chironomus, Anopheles)
and HYMENOPTERA (Incubus, in which follicles are present). The
primitive number of ovarioles in each ovary does not appear to exceed
eight (in Periplaneta), but the number is exceedingly variable as the
following tabulation will show (Imms, 1934):
1 ovariole in each ovary of viviparous DIPTERA (Glossina and
Termitoxenia).
2 ovarioles in each ovary in certain DIPTERA (Melophagus and
Hippobosca), COLEOPTERA, and HYMENOPTERA.
4 ovarioles in each ovary common among the LEPIDOPTERA.
5-7 ovarioles in each ovary in certain ORTHOPTERA (Periplaneta).
100 or more ovarioles in each ovary in certain DIPTERA (Calliphora
and Hypoderma).
200 or more ovarioles in each ovary in certain HYMENOPTERA
(some ants) and COLEOPTERA (Meloe).
2,400 or more ovarioles in each ovary in some ISOPTERA (Termes).
In certain of the sexual females of HOMOPTERA, especially in the plant
lice (APHIDIDJE and PHYLLOXERIDJE), there is but one fully developed
ovary, the other being atrophied.
Oviducts. - In the female the paired oviducts or canals consist of an epithelial
layer of mesodermal origin leading from the gonads to the point of the primitive
gonopore or genital opening. In the EPHEMERIDA, which exhibit a primitive
condition, there is a separate opening for each duct. In the THYSANURA,
PLECOPTERA, and ODONATA they are united in a single cup-like invagination,
but in most insects they unite to form a common duct before reaching the
exterior. This common duct or vagina represents an invagination of the body
wall or an overlapping of the ventral wall of the body and is consequently
ectodermal. Each oviduct in certain insects may be distended posteriorly to
form the vagina which may also be dislended for the retention of eggs or
larvre, as in the tsetse flies, Glossina, and the sheep tick, Melophagus, in which
case the distended portion is termed the uterus.
Spermatheca or receptaculum seminis - sperm pouch or reservoir for storing
the spermatozoa. It is usually ovoid or spherical but may be tubular or even
branched in certain COLEOPTERA, and, being derived from the ectoderm, it
has a chitinous lining. The wall is nonmuscular, and a finger-like gland is generally
attached to it. "It is connected by a slender tube with the vagina. The
sperm finds its way into this reservoir by passing up the vagina after copulation
and out through this spermathecal duct to the spermatheca. As eggs pass
down the vagina, contractions of the tube draw the spermatozoa back down
the duct into the vagina" (Freeborn). In most female insects the spermatheca
is a single organ, but there are two in certain COLEOPTERA (Blaps) and
DIPTERA (Flebotomus and Culex) and three in many other members of the
DIPTERA.
Colleter10l or seM./ic glands. - These organs, consisting of one or two pairs,
open into the lower portion of the vagina. They secrete gelatinous or mucus-