OF WASHINGTON. 409 



parasitic, blood-sucking life upon its host^ ovipositing also in the 

 ' ground or in the debris around the beaver dens, rather than upon 

 the animal itself. Upon an animal like the beaver, with such a 

 heavy and dense fur, there would seem to be no occasion for free 

 life in any stage, and if my present surmise should prove correct 

 it will furnish another forcible illustration of the power of 

 heredity ; for, as this brief review of the parasitic Coleoptera has 

 just shown us, they are none of them completely sedentary upon 

 their hosts in all stages, a result we should expect in derivatives of 

 an order having complete metamorphoses. In other words, none 

 of these parasitic or partially parasitic Coleoptera belong to my 

 first category, and should Platypsyllus breed continuously on its 

 host in all stages, it would prove a marked exception. 



The species of the Staphylinid genus Amblyopinus have been 

 found in the fur of living field-mice in South America, and in that 

 of a living rat in Tasmania, but there is nothing further known of 

 their life-histories or earlier stages. 



I cannot leave the Coleoptera without referring to another case 

 of partial parasitism which has been supposed to occur in the 

 Staphylinidag. Aleochara has been reared from certain Dipter 

 ous puparia ; but, according to the latest observations we have, the 

 habit has not been sufficiently modified to justify any other des 

 ignation than that of predaceous. Mr. D. W. Coquillett has 

 shown (Inseci Life, III, pp. 318319; that the young larvae of 

 Aleochara {Maseochara} valida gnaws its way through the pu- 

 parium of a Syrphid fly ( Copestylum marginatum), feeds in the 

 same, issues as a full-grown larva, and then spins its cocoon and 

 changes to a pupa. Whether within the Dipterous puparium it 

 is the larva or the true pupa which is attacked, the individual is 

 doubtless killed at once upon the entrance of the Aleochara. This 

 could only be considered a very incomplete parasitic life, unless 

 shown to be essential to the development of the Aleochara. In 

 point of fact, the genus has nothing in general structure to denote 

 parasitic life, and the recorded parasitism of A. nitida on An- 

 thomyiid puparia will doubtless prove similar to that observed 

 by Coquillett. 



Thus, true parasitism in the Coleoptera occurs only in the Sty- 

 lopidae and in a few genera of the Rhipiphoridae. In the former 

 and in Rhipidius it is carried a step further than in any other in- 



