LIBRARY

626
COLLEGE ENTOMOLOGY
Nervous System. The nervous system has been extensively studied and described.
Brain - characterized by the highly differentiated stalked lobes or mushroom
bodies and nerve fibers of the pro cerebrum, which are not so extensively
developed in other arthropods; most highly developed in the common
wasps of the genus Vespa in which 1.he calyces or crowns of the
mushroom bodies are folded.
Ventral cord - moderately specialized with from two to three thoracic
and from one to nine abdominal ganglia; in certain cases some of the
latter may be fused, especially in the males.
Reproductive System.
Female - ovaries polytrophic; a variable number of ovarioles: from none or
one to 250 i.n each ovary. Oviducts - a pair unite to form the vagina.
Vagina - may be enlarged posteriorly to form the bursa copulatri;r;. Spermatheca
and a pair of colleterial glands usually presen1.; the former especially
well developed in the queen honeybees.
Male - testes - usually fused together in most forms but separate in the
CHALASTOGASTRA and in the bumblebees and honeybees; each with
double membrane and may contain from one to 250 or 300 seminiferous
tubuli. Vas deferens dilated to form cylindrical or globular vesiculre seminales.
Two ejaculatory canals and a pair of sac-like ducts of the accessory
glands are present. The former are greatly reduced in the honeybee, in
which case the accessory glands empty into the common ejaculatory duct
or ductus ejaculatorius (Imms, 1934). The sperm of HYMENOPTERA
appear to be only female-producing and only this sex is born as a result of
mating, males being the product of unfertilized eggs.
FOSSIL HISTORY
The immediate ancestors of the HYMENOPTERA are thought by Tillyard
(1926) to be the PROTOHYMENOPTERA of the Lower Permian of Kansas,
but Carpenter and other writers do not agree to this ancestry even though an
ovipositor is present in the genus Asthenohymen. The order appears late in
fossil history, the earliest true forms having been taken in the Upper Jurassic.
Remains of the primitive so-called false wood wasps or horn tails of the genus
Pseudosirex are plentiful in Bavaria and in the Middle and Lower Purbeck 1
beds of England, and the ichneumon genus Ephiallites is found in the Upper
Jurassic stones of Montsech, Spain. Cynipids occur in the Canadian Amber of
the Cretaceous (Kinsey 1937) in which also have ceen discovered representatives
of the super families ICHNEUMONOIDEA, SERPHOIDEA, and
CHALCIDQIDEA (Brues 1937). Other important relatives have also been
I Purbeck rocks include fresh-water clays, shales, shell-bearing marls, chert. and oolitic and
sandy strata. The so-called marbles containing many fossil shells and remains of other animals
have been extensively used as building materials. especially for pillars, in the great cathedrals
and churches of Gr::at Britain.