LIBRARY

THE ANATOMY OF INSECTS 27
Genitalia or gonapophyses - the genital organs on segments VIII and XI in
females and IX in males. In the females they may be modified into an exserted
or retractile ovipositor or egg-laying organ of extremely specialized riature and
into a sting in the ants, wasps, and bees, Associated with the male genitalia
may be the claspers (harpe in LEPIDOPTERA) or holding organs; the cedeagus
or penis, the intromittent organ; and the parameres or outer valves. The anus
or anal opening is located in various positions at the extremity of the body. Abdominal
sj)l'racles never exceed more than eight pairs in adult insects. The num·
ber may vary from none in some COCCIDlE to eight pairs in certain HYME­
NOPTERA. A further discussion will be found under the orders.
Glandular openings of different kinds are to be found upon various parts of
the bodies. Sound-producing organs of many types are associated with the body
and its appendages. Stridulating or rasping organs occur in the ORTHOP­
TERA, HEMIPTERA, COLEOPTERA, HYMENOPTERA, and other or·
ders. Sounds made by striking the body or one of its parts against an object
are caused by certain members of CORRODENTIA, ISOPTERA, and COLE­
OPTERA. Vibrating sounds are produced by cicadas, and during flight by
beetles, flies, butterflies, moths, bees, and many other flying insects.
INTERNAL ANATOMY
The study of the internal anatomy of insects has long been a somewhat
neglected field in entomology although some very important contributions were
made in the 18th and 19th centuries by the so-called minute anatomists, Lyonet
(1760), Straus-Durckheim (1828), Dufour (1811-1863) and others. During
the years that followed, many outstanding papers were published by Packard
(1875-1880), Viallanes (1885-1893), Miall and Denny (1886), Heymons
(1892-1901), Holmgren (1895-1916), Janet (1894-1911). and others during the
latter part of the 19th century and by such modern authors as Crampton (1914-
1923), Snodgrass (1921-1935), Bugnion (1921--;1930), Weber (1924-1933),
Wigglesworth (1929-1934), and many others. With an abundance of basic literat.ure
available, the student will have no difficulty in pursuing investigations
not only in the morphology but also in the physiology of insects.
A general discussion of the exoskeleton has already been given. In viewing
the internal systems it must be remembered that the insect body is a compact,
elongated, and somewhat cylindrical organism, the exterior shell or exoskeleton
of which is animated by the internal systems which have no means of attachment
and support other than is afforded by its relatively thin walls. Yet t.he
numerous Ol'gans within are arranged in a symmetrical order which maintain:; a
truly definite pattern throughout the class. A cross section of the body would
show the exoskeleton or body wall; a variable amount of muscular tissues attached
to the whole inside of the body wall and motivating all the external
appendages and internal organs which have to do with movement; the adipose
or fat body, the respiratory or tracheal system located laterally; the digestive
tract, silk glands, sexual organs disposed medially; the seat of the circulatory
system situated dorsally; and the nervous system located ventrally.