December, 18G5.] J_^ 



AN ESSAY TOWARDS A KNOWLEDGE OF BRITISH HOMOPTERA. 



BY THE EEV. T. A. MARSHALL, M.A. 



{Continued from 2oago 126). 



Gen. AcocEPHALUs, Germ. 

 The disparity of the sexes in this genus, and their tendency to run 

 into varieties, are a source of much difficulty. They have been a crttx 

 to the describers, who have, until recently, treated most of the varieties 

 of either sex as specifically distinct. Fallen, in the Hemipt. Sueciae, 

 seems to have perceived their true relations, and his remarks, with the 

 addition of those of Flor, and my own partially successful observations, 

 form the groundwork of the present sketch. The genus is an ex- 

 tremely natural one, characterised by the flattened vertex, more or less 

 triangularly produced between the eyes (except in A. agrestis), — by the 

 ocelli, situated nearer to its anterior than its posterior margin, — by the 

 linear and flattened clypeus, — and by the imperfection of the marginal 

 nervure, which receives the extremities of the longitudinal alary 

 nervures. This deficiency is probably connected with weakness of 

 flight, and will easily be understood by comparing the same organs in 

 the more active and aerial tribes, lassus, Micropsis, and Idiocerus. The 

 males of Acocephalus are smaller than the females, and frequently 

 adorned with dark fascise ; the vertex of the former sex is also less 

 produced. The females are generally brown, more or less irrorated 

 with black, but without distinct fascife ; and to them the difficulty of 

 specific discrimination is chiefly limited. 



A. Yalvula ventralis maris occulta. ^ $ coloribus dispares. (Subg. 

 Acocephalus.^ 



a. Vertex antice subacutus. Antenna) fronte breviores. 



t Vertex pronoto longitudine aequalis, medio baud cariuatus. 



1. — Acocephalus rustictcs, Fab. 



Color variat ; testaceus, sub-viridis, griseus, rufo-brunneus, etiam 

 niger. Genae macula nigra notatae. Vertex dimidia sua inter oculos 

 latitudine non longior. Antennae fronte conspicue breviores. Supra 

 totus subtiliter rugulosus. Abdomen interdum nigrum. Pedes testacei 

 vel brunnei ; femora antica sffipe fusco-maculata, postica fusco-lineata. 

 Alae completae. 



^ . Frons ante oculos, pronotum propc basin, transversim pallido- 

 vittata. Vertex quam in ? conspicue brevior, apice supra impressus. 

 Hemelytra nervis infuscatis quasi striata. 



? . Frons et pronotum nunquam pallido-vittata. Supra unicolor, 

 puuctis plus minus fuscis irroratus. Long. 2|-3 <^; 3-3| lin. ? . 



