AKT. 28 REVISION 0¥ DISONYCHA NORTH OF MEXICO BLAKE 7 



of triangularis, xanthomelas, collata, politula, and probably semi- 

 carhonata, and several more Mexican and Central American species. 

 D. laevigata, known in the West Indies as a garden pest, also belongs 

 to this group of feeders on Amaranthus. They are small, oval insects 

 frequently with lustrous elytra. In spite of their similarity in color- 

 ing, the}'^ differ considerably among themselves and have quite dis- 

 similar aedeagi that do not resemble one another or the aedeagi of 

 the vittate species. 



The remaining 13 species are too distinct to fall readily into 

 groups. Three of them, gldbrata, varicornis, and stenosticha, are 

 closely related to Mexican and Central American species. 



D. gldbrata has two close relatives, nigtita and dorsata Jacoby, the 

 latter with entirely dark elytra. The species gldbrata and dorsata 

 are unlike the other vittate species, except maritima, in having, in 

 their well-marked and typical form, a dark elytral margin. D. gla- 

 hrata and its two close relatives are smooth and shining and have a 

 similarly shaped and similarly marked prothorax. Their aedeagi 

 are nearly indistinguishable. D. gldbrata feeds on Amaranthus, as 

 do the members of the fifth group. In shape these three species ap- 

 pear more closely allied to the fifth group than to the vittate groups. 



D. varicornis, occurring in Texas and southern California, and 

 feeding on Opuntia, is closely related to mexicana Jacoby, although 

 the aedeagi are not alike. Both species have blue elytra but are un- 

 like the rest of the similarly colored species in having a narrower 

 head and prothorax with a broadened apical angle to the explanate 

 margin and with an unusual notching behind the angle. 



D. stenosticha is closely related to (if not identical with) inilitaris 

 Jacoby, a Mexican and Central American species. 



The remaining 10 species, which are not closely related to any 

 others known to me, are: yunctigera, caroliniana, tenuicornis, fig- 

 urata, arizonae, alabamae, adviirdbilis, brevicomis, tnarltima, and 



' ' GEOGRAPHIC VARIATION 



On the Pacific coast there are representatives of only two groups 

 of the vittate species of Disonycha, namely, the alternata and pen- 

 sylvanica groups, and the unique species tnaritimia, which is not like 

 any other known to me. D. varicornis, a species with blue elytra, 

 reaches the Pacific coast, but is known only from Texas, southern 

 California, and Lower California. All the other species of Disony- 

 cha are found east of the Kocky Mountains. Many species have a 

 far w^ider range than has been supposed. As may be expected, 

 species that range from New York to Arizona, such as arizonae 

 and latifrons, show some variation in their different environments. 

 This may be in size, in coloration, and even in punctation, and it 

 has led entomologists to describe as distinct species what are in real- 



