No. J 04.] 117 



to possess eiglit legs, and this feature, of course, removes them from 

 the lice and all other true insects, which have but six legs. 



Their scientiHc classilication places them among the Arachnoidea, 

 in which are included scorpions, spiders and mites. As their body 

 consists of but one piece, instead of being made up of several seg- 

 ments, they fall in the last-named order, the mites, Accwiiia. This 

 order embraces a large number of greatly differing forms that have 

 been arranged in several families to include, as follows : the spinning 

 and the harvest mites {TromhididcB)^ the snouted mites {Bdellidce), 

 freshwater mites {IIydrachnid(£), parasitic mites {Ga?7iasidce), the 

 ticks {/xodid(t'), the beetle mites {OribatidcB), the cheese mites 

 {Tyroglijphidni\ itch mites {Sarcoj)tidce), gall and bud mites {Phij- 

 toptidcf:), and others. The particular family to which this potato- 

 beetle parasite belongs is the Gamasidce, nearly all the species of 

 which in their wide distribution, live parasitically upon mammals, 

 fishes, birds, and insects. The common " chicken-louse," Dermanys- 

 sua avium, which is also found on caged canary-birds, is a well-known 

 species of this family. 



From examples taken from some Colorado potato-beetles in Ohio, 

 in 1873, this little Gamasid mite was described and named by Pro- 

 fessor Riley as Zh'opoda Americana. It was found to be closely 

 allied to a species that had long been known to infest beetles in 

 Europe — the Ur^opoda vegetans, having the same habit of attaching 

 itself to its host by a cord or filament, one end of which was fastened 

 to the anal end of the mite and the other to the beetle. Many had 

 been the surmises of the nature and object of this singular attach- 

 ment in the European species. Some of the old writers had re- 

 garded it as a kind of umbilical cord through which the mite drew 

 its sustenance from its host, and others, that it was a silken thread 

 spun by the mite to serve to fasten it and to prevent its being brushed 

 off by the motions of the limbs of the beetle. Close examination 

 showed, however, that it had no organic structure, that it was fragile 

 and became easily detached; and finally, a French naturalist, M. 

 Dugtis, ascertained that it consisted simply of the viscous and dried 

 excrements of the mite, which could be removed and replaced at 

 every new excretion. 



The discovery of this parasite in Massachusetts in such abundance 

 is gratifying. There is scarcely a doubt that the dead beetles re- 

 ported covered by the "lice," were killed by the attack. The same 

 attack has in former years come under my observation, near Albany, 

 where the beetles were so infested that every portion of their sur- 

 face, including their legs, was so covered as to leave room for no ad- 

 ditions unless they could be superimposed. Although still upon the 

 potato leaves they were not feeding, but were evidently greatly 

 debilitated and near their end. The occurrence of the parasite so 

 early in the season (May) is also favorable, for ever}' beetle that is 

 now dcstroN'ed may serve to lessen the number of the pest later in 

 the year by several hundreds. The present brood of beetles will be 

 followed by at least one other during the year, and each female con- 



