INTERNAL ANATOMY OF INSECTS. 1?1 



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 Rosa, 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 

 Abietis\ which appeared never to be ovo-viviparous d . 



With regard to scorpions, 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 c . Thepupiparous 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. d Ibid. 128. 



* N. Diet, if Hist. Nat. xxx. 426. ' VOL. III. p. 64. 



