OF WASHINGTON. 401 



a clear discussion of any subject, and this is essentially true in the 

 present case. The original Greek meaning of the term parasite, 

 which has come down to us with little change through all lan 

 guages, was " one who eats at another's table," and in etymologi 

 cal as well as common usage the term more properly belongs, 

 entomologically, to the true lice (Pediculina) and the Mallophaga ; 

 for these are true hangers-on, living as degraded and dependent 

 guests, without necessarily injuring their host. Yet most ento 

 mologists at the present day, if asked what they consider to be 

 true or essential parasites among insects, would, undoubtedly, 

 cite the entomophagous Hymenoptera, including the families 

 Ichneumonidse, Braconidae, Proctotrypidas, Chalcidida?,, some 

 sections of the Cynipidas, and the Evaniidae. Latreille's Para- 

 sita* as representing these and many other insects, is an invalid 

 group and essentially obsolete. 



What is true of parasites as a whole, for both the animal and 

 vegetal kingdoms, is equally true of parasitism in insects. Para 

 sites are not divisible into natural groups. They are found in 

 families of various Orders, while not infrequently they occur in 

 families, or even genera, which are normally non-parasitic. It 

 would be folly, therefore, to attempt any natural or genetic classi 

 fication. 



It is equally difficult to formulate any intrinsic classification of 

 the subject, based upon the peculiar kind of parasitism. While 

 we find every gradation exemplified, from the most simple asso 

 ciation, the beginning of dependence, to the most complete and 

 absolute dependence ; yet the steps in this process are often intan 

 gible and the actual facts extremely complicated. But a certain 

 division of these parasitic characteristics as they are presented to 

 us among insects is possible, and will be found useful. One that 

 has been commonly used and which at once suggests itself is the 

 division into ecto- and ento-parasites ; i. e., into those which are 

 external and those which are internal feeders. These are, how 

 ever, unnecessary and artificial divisions, entomologically con 

 sidered, though having a certain value as contrasting the omnipres 

 ent and essentially internal entozoan and bacterian parasites with 

 the equally omnipresent external Pediculina and Mallophaga. 



Another division has been commonly accepted, viz , that into 

 parasites proper and commensals or inquilines. It seems to me 



