580 



INSECTS AND ARACHNIDA. 



objects of great beauty, on account of the regularity of their 

 form, and the symmetry of the markings on their surface (Fig. 

 296). The most interesting belong for the most part to the 

 Lepidopterous order ; and there are few among these that are not 

 worth examination, some of the commonest (such as those of the 



FIG. 296. 



Eggs of Insects magnified : A, Pontia napi ; B, Vanessa urticce ; c, Hippardiia tithous ; 

 D, Argynnis Latiionia. 



Cabbage-butterfly, which are found covering large patches of the 

 leaves of that plant) being as remarkable as any. Those of the 

 puss-moth (Cerura vinula), the privet hawk-moth (Sphinx ligustri), 

 the small tortoise-shell butterfly (Vanessa urticce}, the meadow- 

 brown butterfly (Hipparchia janira), the brimstone-moth (Rumia 

 cratcegata), and the silk- worm (Bombyxmori\ may be particularly 

 specified ; and from other orders, those of the cockroach (Blatta 

 orientalis), field cricket (Acheta campestris\ water scorpion (Nepa 

 ranatra), bug (Cimex lectularius), cow- dung fly (Scatophaga ster- 

 coraria), and blow-fly (Musca vomitoria). In order to preserve 

 these eggs, they must be mounted in fluid in a cell ; since they 

 will otherwise dry up and become misshapen. The remarkable 

 mode of reproduction that exists among the Aphides must not 

 pass unnoticed here, from its curious connection with the non- 

 sexual reproduction of Entomostraca ( 369) and Rotifera ( 279), 

 as also of Hydra ( 301) and Zoophytes generally, all of which 

 fall specially, most of them exclusively, under the observation of 

 the Microscopist. The wingless Aphides which may be seen in 

 the spring and early summer, may be considered as larvae or 

 pupse (the earlier states of this insect not being distinguishable 

 from its perfect form, except by their want of wings) ; and these 

 larvse, which, though commonly designated as females, are really 

 of no sex, give origin to a brood of. similar wingless Aphides, 

 which come into the world alive, and which, before long, go 

 through a like process of multiplication. As many as from seven 

 to ten successive broods may thus be produced in the course of 

 a single season ; so that from a single Aphis, it has been calcu- 

 lated that no fewer than ten thousand million millions may be 

 evolved within that period. In the latter part of the year, how- 

 ever, some of these larval Aphides attain their full development 

 into winged males and females, by which the true generative 

 process is performed, whose products are eggs, which, when 



" Me"moire sur les Objets qui peuvent etre conserves en Preparations Microscopiques" 

 (Paris, 1856), which is peculiarly full in the enumeration of the objects of interest 

 afforded by the class of Insects. 



