1949] 
W erner — Epicauta 
99 
the Kockies, an altitudinal segregation acts and the same 
mechanism may act in Arizona where the ranges overlap. 
Where maculata and bispinosa overlap, or where one has 
differentiated from the other as the case may be, strict 
adherence to host plant specificity serves to segregate the 
two in the adult stage and present a barrier to inter- 
breeding. 
Present-day conditions in Arizona are exceedingly 
favorable for study of host specificity of Epicauta. A 
good proportion of the land is heavily grazed, the only 
comparatively untouched parts of many areas being along 
the main roads where the vegetation is protected by 
fences. Any adults of the herb-feeding species that 
emerge congregate on the roadside plants. A fairly high 
percentage of the individuals in the area must assemble 
here. Being parasitic and living in an area of uncertain 
rainfall, the number of individuals varies greatly from 
year to year. When a patch is found which supports 
blister beetles it usually has several species within a small 
area. Under such conditions one would expect any pos- 
sible hybridization to occur. When none does occur, it is 
certainly an indication that there is some barrier, be it 
intersterility, micro-ecological isolation on host plants or 
even psychological. 
Therefore the author maintains that the occurrence of 
maculata and bispinosa side by side on different food 
plants is a clear indication that they are distinct popula- 
tions and since no intergrades have been found to indicate 
hybridization, prefers to treat them as species. At the 
same time, he feels certain that as more becomes known 
about both, this food plant isolation will be found not to 
be the primary factor in keeping the two separate. 
Epicauta cinerea (Forst.) 
Meloe cinereus Forster, 1771, Cat. Animals N. Am.: 62. 
Lytta fissilabris LeConte, 1850, Agassiz Lake Superior 
4: 232 ; 1853, Proc. Acad. Nat. Sci. Phila. 6: 339. (new 
synonymy) 
Epicauta fissilabris, Horn, 1873, Proc. Am. Phil. Soc. 
13 : 102. Werner, 1945, Bull. M.C.Z. 45 : 456. 
