BENEFICIAL INSECTS 233 



mouth, becomes reduced to a dry, non-adhesive powder ; 

 it is harder than beeswax, owing to its fibrous structure. 



Here we must bid farewell to the useful insects, not 

 because we have enumerated them all, but on account of 

 the exigencies of space. Of bees as honey producers and 

 of silkworms we have made no mention : in general, their 

 utility is known to everyone, and their culture has become 

 so specialised that a very considerable literature is devoted 

 to them. The parasitic and predaceous insects mentioned 

 in Chapter VIII., together with a multitudinous host, not 

 mentioned, are also man's friends. Many insects, which 

 in the main are decidedly injurious, have some points in 

 their favour ; the much despised house fly is of considerable 

 utility as a scavenger ; cockroaches, despite their loathsome 

 habits, rid our houses of bed bugs, and examples innumer- 

 able might be quoted. Though man is very deeply indebted 

 to some few insects, not only for his luxuries but for his 

 everyday needs, it is impossible, despite the wish to do so, 

 to contend that insects on the whole can be considered 

 in any other light than as inveterate enemies. 



