554 



PHYSIOLOGY. 



Lepidoptera. Many of them also live in the caterpillars of several 

 butterflies. We cannot yet determine with certainty whether these 

 enemies of the vegetable feeders are as select in the choice of particular 

 insects as the latter are in the choice of their vegetable nutriment ; yet 

 this appears to be the case among the larger Ichneumons. Thus, for 

 instance, Ophion amiclus, Fab., lives upon the caterpillars of Sphinx 

 plnaslri, Ichneumon lapidator in those of Noctua Typhce. The large 

 families of Sphecodea and Crabronea also destroy the larvae of 

 Lepidoptera to use them as food for their young, as we have frequently 

 before mentioned. It is remarkable that all these enemies of other 

 insects belong to the order of the Hymenoptera, of which we already 

 know that its members, by visiting flowers, contribute directly to the 

 advance and increase of the vegetable kingdom. We have now, there- 

 fore, also seen that they even go still further in promoting this, as they 

 destroy and remove insects inimical to plants. This double function 

 we perceive also in the majority of the Diptera, in as far as these iu 

 their imago state visit blossoms, but as larvae thrive frequently in or 

 upon insects that feed upon vegetables. These two orders it is, 

 therefore, especially, which exhibit to us the closest connexion of insects 

 to the vegetable kingdom, as they in a double manner promote the 

 increase of plants. 



308. 



With regard to the relation of insects to the vertebrata, we may 

 observe, that the same holds good with respect to fishes as what we 

 have observed upon the Mollusca. B\ r their living especially in water 

 and in the sea, they are removed from the direct influence of insects, 

 and only those fishes which inhabit fresh water appear to lie in wait 

 for the larvae of the Ephemera, Semblodea, Libellulce, and gnats, and 

 use them as food. It has not yet been observed that insects are 

 parasitic upon fish, yet the larger Dytici and other water-beetles doubt- 

 lessly feed upon the spawn of fishes, and even Dyticus latissimus, as 

 well as its larger congeners, attack small fishes and eat out their eyes. 



Nor do the reptiles either supply insects with food or serve them to 

 dwell upon, unless, which is very probable, the spawn of frogs is fre- 

 quently consumed by the large predaceous water beetles. These 

 beetles also frequently devour the little tadpoles, whereas insects supply 

 the reptiles that live upon land, namely, the frogs, salamanders, lizards, 

 and small snakes, with their sole and favourite food. 



