358 PHYSIOLOGY. 



alone. The same is the case with the parasites, particularly 

 the constant ones, whereas those which are merely partially 

 so, for instance, the gnats, the flea, &c., frequent all the 

 warm-blooded mammalia of various families and orders. The 

 partial parasites of insects and the Mollusca are also found 

 tolerably limited to one species, or at least to but few, but 

 two or three. Few animals are so much restricted to one and 

 the same kind of food as insects. Thus the leaf-consuming 

 caterpillars have generally each its distinct plant, and indeed 

 some are so scrupulous that they reject all other plants, and 

 will even starve to death rather than touch any but their 

 usual food. Besides the crude unprepared juices which are 

 found in the stem the more fully developed ones of the flower 

 yield nutriment to many insects. All the Lepidoptera, with- 

 out exception, suck the nectar of blossoms, the same with the 

 wasps, bees, and many other Hymenoptera, and, lastly, among 

 the Diptera, the Bombylodea, and Syrphodea, but they do 

 not restrict themselves to certain plants, but frequent all, and 

 those which are the richest in honey are the most agreeable to 

 them. Some, as the wasps, lap also the fresh juices of ripe 

 fleshy fruits, particularly those which are sweetened by the 

 influence of the sun upon a wounded part. 



We may also here briefly state that many beetles, for 

 instance, the Lepturce, Coccinellw, &c., lap the honey of 

 flowers, and that others prefer the crude juices of the stem, 

 as Lucanus, &c. that of the oak. 

 b. Corrupt vegetable substances. 



There are not many insects which resort to these. If we 

 did not here include the juices produced by the rapid putre- 

 faction of fungi, or the in general almost fermenting juices 

 of mature fungi, upon which the larvae and perfect insects of 

 the numerous family of Mycetophthires feed, we should 

 scarcely find genera that have recourse to such nutriment. 



220. 



The first change of the food, and which is as it were a preparation 

 for digestion, takes place during the mastication or sucking by the 

 intermixture of the secretion of the salivary glands. These organs, as 

 we find at 112, are found in all haustellate and many mandibulate 



