INSECTS IN GENERAL. 7'3 



substances on which the larvae are to feed, A kind of jelly, 

 or gluten, serves as a bed for the eggs of some insects, which 

 are committed to the water. Oily substances are secreted by 

 some insects, but their precise nature has not been ascertained, 

 nor whether peculiar organs are appropriated to their secre- 

 tion. The larva of the chrysomela popuU, and some other 

 insects, emit a milky fluid from different parts of their 

 bodies. Of silk, honey, and wax we must defer any notice, 

 only remarking that the latter production is not peculiar to 

 bees, and that, in many other insects, it is a general transuda- 

 tion from the body ; it also appears to form a constituent 

 part of some insects that do not secrete it. A poisonous 

 fluid, producing very unpleasant effects, is secreted by many 

 of these animals. The acid of ants is a very curious pheno- 

 menon, as will be seen in the proper place. An acid has 

 been obtained from silkworms, called bombic acid. 



The powerful scents emitted by insects, whether agreeable 

 or otherwise, are numerous beyond measure. Some are pecu- 

 liar to certain parts of the body, some exhaled from the 

 whole. Sometimes their vehicle is a fluid secretion, and some- 

 times gaseous effluvia : of phosphoric secretions, we shall speak 

 in treating of the glow-worm. 



Fat is found in great abundance in insects in the larva 

 state, and more or less in the imago. In the former, it occu- 

 pies the whole of the interior, except the space required for 

 the muscles and internal organs, which it surrounds. It is 

 contained in numerous floating membranes, which sometimes 

 appear like small globules, and sometimes like a thick muci- 

 lage. Its colour is white, but sometimes yellow or green. 



That insects perspire, appears more than probable. A 

 quantity of fluid escapes from them in the pupa state, which 

 has been proved by experiment. The want of a urinary dis- 

 charge renders it probable that the imago also perspires. But 



