OP GENERATION. 31 1 



were all of the female sex*. But, according to Bonnet t and Do Geer, 

 male individuals appear in August, upon the decrease of the tempera- 

 ture, which then copulate with the females, whereupon the females lay 

 eggs, from which, in the ensuing spring, young female Aphides are 

 brought forth, which re-produce female individuals until the autumn, 

 without they or their young having had any intercourse with the other 

 sex. Bonnet j even considered that the eggs of the females was but 

 a procrastinated development of the young produced by cold, and this 

 supposition is confirmed by Kyber's observations, who found them 

 never to lay eggs when removed to warmed apartments. 



These facts, which, after the repeated observations and experiments 

 of Bonnet, De Geer, Reaumur, and Kyber, may be considered as incon- 

 trovertible, perfectly prove the possibility of a spontaneous develop- 

 ment ; at least the opinion of some naturalists, that the impregna- 

 tion of the great grandmother extends to the tenth generation, is 

 much more incomprehensible than the other. A second instance is 

 furnished, according to former general assertion, by the genus Psyche, 

 Latr., which contains the cased caterpillars. Reaumur was probably 

 the first who made the observation that the female, which he mistook 

 for a caterpillar, because it was apterous, laid eggs without a male 

 having been near her. Schiffermuller subsequently observed the 

 same ||, as well as Pallas % who described the species upon which he 

 made his observations as Phalcena yylophthorum. Stimulated pro- 

 bably by these communications, Rossi undertook numerous experiments 

 upon this obscure mode of propagation of the cased caterpillars, which, 

 according to Ochsenheimer **, " were conducted with the greatest care," 

 and yet produced the same results. Other witnesses were found in 

 Bernoulli ft, who, among other instances of the kind, mentions one of 

 a cased caterpillar, in Kiihner |J and Schrank . Nevertheless Zinken, 

 gen. Sommer has proved, by a long series of observations, that in these, 



* Germar's Mag. der Entom., vol. i. part ii. p.] 4. t Insectologie, torn. i. 



J Contemplations de la Nature, torn. i. 



M(5moires, edit, in 8vo, torn. iii. part i. p. 194. 



|| Verzerchniss der Schmet. der Wiener Gegend. 4to, 17G6, p. 288. 



If Nova Acta, toin. iii. (1767) p. 430. 



* Schmettcrlinge von Europa, vol. iii. p. 178. 

 ff Me'm. de I'Aca.'i. Roy.de Berlin, 1772, p. 24. 

 U Naturforscher, St. VII. (1780), p. 171. 

 Fauna Boica, vol.ii. part ii. (1802), pp. 94 and 97. 



