Microscopical Essays, 273 



iby the laws of Divine order, to place their eggs on fubjecls proper 

 for the larva which are to proceed from them. 



Among thofe which feed on vegetables, fome fink themfelves 

 in the earth, deftroy the roots of the plants, and do considerable 

 injuries to our gardens, &c. The food of others is dry and 

 hard ; they pierce the wood, reduce it. to powder, and then feed 

 on it ; fome, as the coffus; deftroy and attack the trees, while the 

 food of others more delicate is the leaves. The leaf is eat in a 

 different manner by different infecls ; fome eat the whole fub- 

 f iance, while others feed only on the parenchemous parts, which 

 are contained between it's fuperncial membranes, forming within 

 fide the leaf paths and galleries. Thefe infecls are not always 

 content with the leaf, but attack the flower alfo : even this food 

 is too grofs for many ; the bee, the butterfly, the moth, as well 

 as feveral fpecies of flies, feed only on the honey, or finer juices, 

 which they col i eel from flowers. Fruits, grains, and corn, are 

 not free from them ; they divide them with us, and often deprive 

 us of large quantities. We are continually finding the larva of 

 fome infect in pears, plumbs, peaches, and other fruit ; there is, 

 indeed, no part of a plant which does not ferve as food to 

 different infecls ; fome have one kind of plant marked out for 

 them to inhabit and feed on, others have another aiTigned to 

 them, on which, and no other, they will feed ; each has it's appro- 

 priate food, and though the parent animal Cats not at all, or 

 lives upon food entirely different, yet (he is guided, as we have 

 already obferved, to depofit her eggs on that peculiar fhrub or 

 plant that will be food for her young ; while fome, more vora- 

 cious than the reft, feed upon all with equal avidity. The grylus 

 migratorius, a few years fmce, poured out of Tartary in fuch 



L 1 quantities,- 



