INTERNAL ANATOMY OF INSECTS. 171 
the mother a . As these flies are all carnivorous, and 
their office is to remove putrescent flesh, you may see at 
one glance the object of Providence in this law of 
nature — that no time may be lost, and the animal ex- 
ercise its function as soon as it is disclosed from the 
matrix. 
The Aphides, so fruitful in singular anomalies, are 
ovo-viviparous, as I have before hinted b , at one period 
of the year, that is during the summer, but strictly ovi- 
parous at its close. From the experiments of De Geer, 
however, upon Aphis Mosce, it would appear that this 
faculty is not conferred upon the same individuals, but 
only upon those of different generations of the same 
species ; all the generations being ovo-viviparous except 
the last, which is oviparous c : nor does it appear, as 
has been sometimes imagined, that it is common to the 
whole genus. De Geer observed a species in the fir, 
which makes curious galls resembling a fir cone {Aphis 
Abielis), which appeared never to be ovo-viviparous d . 
With regard to scorjrions, it does not seem clear that 
they are always ovo-viviparous: M. Dufour twice found 
in the midst of the eggs nearly mature, a young scorpion 
which appeared to him at large in the cavity of the abdo- 
men ; it was so large that it was difficult to comprehend 
how it could possibly be excluded from the animal, with- 
out an extraordinary operation e . The pupiparous insects 
(Hippobosca, &c.) have been sufficiently noticed before f . 
2. I have already in several of my former letters stated 
a De Geer vi. 63—. b Vol. I. p. 175. 
c De Geer iii. 70—. " lUd. 128. 
" JV. Diet. d'Hist. Nat. xxx. 426—. ' Vol. III. p. 64- 
