OSBORN AND BALL THE GENUS PEDIOPSIS. 



THE GENUS PEDIOPSIS. 

 (A Review of the North American Species.) 



BY HERBERT OSBORN AND ELMER D. BALL. 



This genus is one of the most difficult of the Jassoidea in which to 

 define species, for although with fresh specimens there is little diffi- 

 culty in separation, and in most cases the host plant of itself will 

 decide as between the species most likely to be confused, still, as a 

 group, the species are remarkably alike in structural characters, the 

 variations being usually those of degree rather than of kind. The 

 genitalia, the ordinary recourse when other characters fail, are utterly 

 valueless, the variation for the whole group being scarcely more than the 

 ordinary variability in a species. 



The few structural characters available, together with the color 

 have, however, been found sufficient to readily and accurately sepa- 

 rate those species under observation in a series of life-history studies 

 in the group,* and as the result of the determination of the range of 

 variation in these species, it has been found much easier to refer some 

 of the more widely variable examples of other species to their proper 

 places. 



The greatest difficulty in working over material in this group arises 

 from the fact that the green color in most of the green species 

 " fades" or changes to a dirty yellowish when immersed in alcohol or 

 on exposure to a strong light, thus altering very much the appearance 

 of the specimen. 



The black marking on the propleura has been found to be fairly 

 constant in most of the species in which it exists, and is the readiest 

 means of separating some species; but as it is often only a sexual 

 character and sometimes fails when it is needed the most, as in some 

 of the lighter colored females o{ ferrugijwides, it has been thought best 

 to depend on other characters for the synopsis and thus leave it as a 

 sort of check, except in the case of occidentalis where, with our imper- 

 fect knowledge of the species, it appears to be the best character avail- 

 able for the purpose. 



* Dav. Acad. Sci., Vol. VH., 1897, and la. Exp. Sta. Rept., 1897. 



