162 INTERNAL ANATOMY OF INSECTS. 
the female Aphides in their natural state, I mean those 
of the summer or viviparous broods, have intercourse 
with the male. I think I have noticed males amongst 
them; but they seem to become most numerous in the 
autumn, preparatory to the impregnation of the ovipa- 
rous females. The object of this law of the Crearor 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 intervenes, 
and the eggs increase to four times the size which they had 
attained at that period, before they are extruded’. The 
time that is required to lay the whole they are to pro- 
duce, varies also in znsects. In this respect they may be 
divided into two great classes: —those namely which de- 
posit the whole at once, as Ephemerina, Trichoptera, &c., 
and those which deposit them in succession, occupying in 
this operation a longer or shorter period. Many in the 
Jirst class, as the Trichoptera (Phryganea L.) or case- 
worm-flies, envelope their eggs in a gelatinous substance °, 
which renders their extrusion in a mass more easy. Of 
the second class, which includes by far the greater propor- 
tion of insects, some exclude the whole number in a very 
short period, others require two or three days or a week, 
as the cockroach‘; and others, as the queen-bee, not 
of the last generation less so than the first. Latr. Hist. Nat. des 
Crust. et Ins. x1. 292. 
* See more on the subject of fecundation. Vor. II. p. 168—. 
> N. Dict. a Hist. Nat. xxx. 426. © Vor. III. p. 68. 
4 De Geer iii, 533.” 
