1G8 INTERNAL ANATOMY OF INSECTS. 
of Branchiopod Crustacea a . It is worth observing 
whether the female Aphides in their natural state, I mean 
those of the summer or viviparous broods, have inter- 
course with the male. I think I have noticed males 
amongst them ; but they seem to become most nume- 
rous in the autumn, preparatory to the impregnation of 
the oviparous females. The object of this law of the 
Creator is probably the more ready multiplication of 
the species ''. 
As to the period of gestation, most insects begin to lay 
their eggs soon after fecundation has taken place : but 
in some Arachnida, as the Scorpion, which seems to be 
both oviparous and ovo-viviparous, nearly a year inter- 
venes, and the eggs increase to four times the size which 
they had attained at that period, before they are ex- 
truded c . The time that is required to lay the whole 
they are to produce, varies also in insects. In this re- 
spect they may be divided into two great classes: — those 
namely which deposit the whole at once, as Ephcmerina, 
Trichoptera, &c, and those which deposit them in suc- 
cession, occupying in this operation a longer or shorter 
period. Many in the first class, as the Trichoptera or 
caseworm-flies, envelope their eggs in a gelatinous sub- 
stance d , which renders their extrusion in a mass more 
easy. Of the second class, which includes by far the 
a N. Diet. d'JIUt. Nat. ix. 125. Bonnet and Jurinc both found 
that the female Aphides and Branchiopods that were fertile without 
the usual intercourse of the sexes were less fruitful than their mother, 
and those of the last generation less so than the first. Latr. Hist. 
Nat. det Crust, el Ins. xi. 292. 
i> Sec more on the subject of fecundation, Vol. II. p. lo4— . 109 — . 
° N. Diet. d'llist. Nat. xxx. 426. d Vol. III. p. C8. 
