168 INTERNAL ANATOMY OF INSECTS. 



of Branchiopod Crustacea a . It is worth observing 

 whether the female Aplrides 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 b . 



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 whoJe 

 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 Ephemerina, 

 Trichoptera, &c., and those which deposit them in suc- 

 cession, occupying in this operation a longer or shorter 

 period. Many in thejirst class, as the Trichoptera or 

 case worm-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 



3 N. Diet. d'Hist. Nat. ix. 125. Bonnet and Jurine 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. dcs Crust, et Ins. xi. 292. 



b See more on the subject of fecundation, VOL. II. p. 154. 169 . 



tf. Diet. d'Hist. Nat. xxx. 426. " VOL, III. p. 68. 



