ANATOMY AND PHYSIOLOGY 145 
Parthenogenesis.—Reproduction without fertilization is a 
normal phenomenon in not a few insects. This partheno- 
genesis may easily be observed in plant lice. In these insects 
there are many successive broods consisting of females only, 
which bring forth living young; at definite intervals, however, 
and usually in autumn, males appear also, and fertilized eggs 
are laid which last over winter. This cyclic reproduction, by 
the way, is known as heterogeny. Among Hymenoptera, 
parthenogenesis is prevalent, usually alternating with sexual 
reproduction, as in many Cynipidee. In some Cynipide, how- 
ever, males are unknown; such is the case also in some Ten- 
thredinide. The statement has long been made that the un- 
fertilized eggs of worker ants, bees and wasps produce invari- 
ably males; it has been found recently, however, that the par- 
thenogenetic worker eggs of the ant Lasius niger may produce 
normal workers (Reichenbach, Mrs. A. B. Comstock). Males 
may, of course, result from fertilized eggs, as in the honey bee, 
according to Dickel, who maintains, indeed, that all the eggs 
laid by the queen bee are fertilized. Parthenogenesis has been 
recorded as occurring also in a few moths, some Coccidz and 
many Thysanoptera. 
Pzedogenesis.—In Miastor and some species of Cecido- 
myia, young are produced by the larva. This extraordinary 
form of parthenogenesis is termed pedogenesis, and is limited 
Fic. 186. 
Young pedogenetic larve of Miastor in the body of the mother larva. Greatly en- 
larged.—After PAGENSTECHER. 
apparently to the family Cecidomyiide. The pzdogenetic 
larve of Miastor (Fig. 186) develop before the oviducts have 
appeared and escape by the rupture of the mother. After 
several successive generations of this kind the resulting larvee 
pupate and form normal male and female flies. The pupa of 
a species of Chironomus occasionally deposits unfertilized 
eggs, which develop, however, in the same manner as the fer- 
tilized eggs of the species. 
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