13 



the best American authorities on the Coleoptera of North America. 

 There are a number of examples where a common enemy of forest 

 trees has been identified from descriptions or from observation in the 

 field as a certain species, and after a great deal has been published 

 under the erroneous names it has been found upon comparison with 

 the types that it was quite a different thing, with different habits from 

 the species to which the name properly belonged; and in some cases 

 what was supposed to represent a well-known species was even found 

 to be undescribed. It will, therefore, be readily seen how important 

 it is for the species we write about to be accurately identified, and how 

 necessary to have a numbered specimen to refer to for future correc- 

 tions or to send to a specialist for authentic identification. 



It is always of the greatest importance to observe the character of 

 the work of the insects when found in their natural feeding or breed- 

 ing places; and, whenever possible, specimens of the work should be 

 secured for the collection, especially the work of wood and bark bor- 

 ing species and that showing special or characteristic injuries to the 

 foliage, etc. ; and each should, as with the insect specimens, be accom- 

 panied by the note number. 



It is also important for the beginner to collect large numbers of 

 specimens both of the insect and its work whenever the opportunity 

 offers. For, even if there should be more than he needs for his own 

 collection, they may be specially valuable for exchange with other 

 collectors for desirable material from other localities and countries. 

 One of the commonest mistakes made by most young collectors, and. 

 for that matter, many older ones, is the failure to avail themselves of 

 the very first opportunitv to collect an abundance of material relating 

 to any desirable species. It must be remembered that because an 

 insect is common at one time or place it does not always follow that 

 it will continue to be so or that it is common in other places. Indeed, 

 the reverse is the rule. A period of great abundance is usually fol- 

 lowed by a period of great rarity, or. as has sometimes happened, 

 almost complete extinction. 



The collector should be constantly on the lookout for the natural 

 enemies of the principal injurious species. One class of the enemies 

 of insects consists of parasitic Hymenoptera. Diptera. etc., found in 

 the adult larval or pupal stage associated with their host, the larvae 

 as external or internal feeders on the larvae, pupae, or adults of the 

 injurious species, and the adult parasites ovipositing on or in the vic- 

 tims, or in the bark or other infested parts of the plant. The other 

 class of insect enemies of insects are predatory species oi Coleoptera. 

 Hemiptera, Hymenoptera. and other kinds of insects which attack 

 and kill their victims, and either devour them or suck out the liquid 

 parts of their bodies. There are also insect diseases which may be 

 indicated by a white powdery substance on the bodies of the dead 



