v J METAMORPHOSES OF INSECTS. 87 



In the consideration then of this question, we must 

 rely principally on Embryology and Development. 

 I have already, referred to the cases in which species, 

 very unlike in their mature condition, are very similar 

 one to another when young. Haeckel, in his " Natur- 

 liche Schb'pfungsgeschichte," gives a diagram which 

 illustrates this very well as regards Crustacea. Pis. I 

 4 show the same to be the case with Insects. 



The Stag-beetle, the Dragon-fly, the Moth, the 

 Bee, the Ant, the Gnat, the Grasshopper, these and 

 other less familiar types seem at first to have little 

 in common. They differ in size, in form, in colour, 

 in habits, and modes of life. Yet the researches of 

 entomologists, following the clue supplied by the 

 illustrious Savigny, have proved, not only that while 

 differing greatly in details, they are constructed on 

 one common plan ; but also that other groups, as 

 for instance, Crustacea (Lobsters, Crabs, &c.) and 

 Arachnida (Spiders and Mites), can be shown to be 

 fundamentally similar. In PL 4 I have figured the 

 larvae of an Ephemera (Fig. i), of a Meloe (Fig. 2), 

 of a Dragon-fly (Fig. 3), of a Sitaris (Fig. 4), of a 

 Campodea (Fig. 5), of a Dyticus (Fig. 6), of a Termite 

 (Fig. 7), of a Stylops (Fig. 8), and of a Thrips (Fig 9). 

 All these larvse possess many characters in common. 

 The mature forms are represented in the corre- 

 sponding figures of Plate 3, and it will at once be seen 

 how considerably they differ from one another. The 

 same fact is also illustrated in Figs. 48 55, where 

 Figs. 48 51 represent the larval states of the mature 

 forms represented in Figs. 52 55. Fig. 48 is the 

 larva of a moth, Agrotis snffusa (Fig. 52); Fig. 49 of 



