Mr. J. Walton on the (jeniis lihynchites. 83 



antennse does not warrant in my opinion the dismemberment of 

 a natm'al genus of insects. I may notice, that the antennse in the 

 females of this genus are more or less distinctly longer than in 

 the males ; the males have the antenna and its articulations 

 shorter and stouter than the females : these sexual differences 

 are very evident in the two species R. cequatus and H. aeneuvirens. 

 The dilated posterior femora in the males of the present species 

 can only be regarded as a sexual character : other organs are 

 equally modified or varied in their structure by sexual differences, 

 as I shall have occasion to notice in this and other portions of 

 my communication. 



2. R. megacephalus, Germ. 1824. 



— Mannerheimi, Hummel. 



— ItEvicollis and cyaneopennis, Steph. 1831. 



— constrictus (Waltl.), Schonh. 1839. 



Of species No. 2* I sent many specimens to Germar, whose 

 authority I have for the fh-st two names quoted : this author says, 

 " it is without doubt my R. megacephalus." From Schonherr I 

 have received a specimen of the R. constrictus of his work, and a 

 comparison of that with the lavicoUis and the cyaneopennis of 

 Stephens leaves no doubt in my mind of the accuracy of the 

 above synonyms. 



I have found this species plentifully on the birch [Betula alba) 

 in the middle of the mouth of July. 



3. R. puhescens, Fab. (Mus. Banks.), Herbst, Germ., Steph., 



Schonh. 

 Cure, puhescens, Fab. Syst. Ent. 1775. 



— puhescens. Marsh. 



R. {(^) cavifrons (Chevr.), Schonh., Steph. Man. 

 Att. puhescens, Mus. Kirb. 



M. Chevi'olat, when in England, separated, as being his R. ca- 

 vifrons, certain specimens from among a series in Mr. Waterhouse's 

 cabinet, Avliich were there labelled puhescens. I have likewise re- 

 ceived a specimen of R. cavifrons from M. Chevrolat; these spe- 

 cimens are undoubtedly all males of R. puhescens, which differ 

 from the females in lia\dng the head oblong, anteriorly broad, 

 posteriorly narrowed, with the forehead more convave : the fe- 

 male has the head broader and shorter, less concave between the 

 eyes, and of a transverse quadrangular form — sexual differences 

 which are more or less distinctly traceable in very many species 

 of this genus. 



The c? and ? of R. ophthalmicus (a very nearly allied species) 



* Throughout the paper 1 shall speak of the species according to the 

 number, in preference to any name, to prevent confusion. 



G2 



