Sexual DimorpMsm in the Rutelid genus Parastasia. 487 



of the head and the anterior half of the elytra which are 

 black, the red posterior part being paler at the extremity. 

 Dr. Ohaus mentions a female coloured practically like this, 

 which is probably exceptional but affords further proof of 

 their specific identity. The structure of the horns in the 

 two sexes is however probably constant, the male showing 

 the same difference as in P. hetcrocera but with a some- 

 what greater development. Under these circumstances 

 Westwood's name will of course have to give place to that 

 given by Erichson. 



Erichson's description of the related P. niticlula is from 

 a male specimen, as shown by the form of the cephalic 

 processes. The only coi'respondiug specimen I have seen 

 is in M. Oberthtir's collection, which also contains two 

 individuals of the other sex, a third being in the British 

 Museum. These three females agree in having an apical 

 orange band upon the elytra, the male being without 

 marking. The coloration of the sexes thus reverses the 

 condition prevailing in P. keterocera, which is very 

 remarkable considering tlie intimate structural relation- 

 ship of the two. In the three closely related species, 

 dimidiata, keterocera and nitidula, we accordingly find the 

 elytral band occurring noi'mally in the male only in one, 

 in both sexes in another, and in the female only in the 

 third. P. nitidula may prove to be variable, like the 

 other two, in coloration, but the normal condition seems 

 to be sufficiently indicated by the five known speci- 

 mens. Both sexes of this species are distinguished by the 

 bronzy lustre upon the elytra, no other known member of 

 the genus being in any degree metallic. 



These three species form a section of the genus differ- 

 ing from the previous one in no important particular but 

 the greater development of the cephalic and mesosternal 

 processes. Another section consists of species in which 

 these are not prolonged but the structure of the claws 

 differs entirely in the two sexes, those of the male being as 

 in the last two sections, while in the female they are all 

 undivided.* To this group belongs the commonest species 

 of the genus, P. confiiiens, Westw., the sexes of which 

 previously separated as jjilca and rugosicollis have already 

 been brought together by Dr. Ohaus. In this insect, 

 besides the difference in the claw-structure, there is a 

 striking difference both in colour and sculpture, the females 

 being deeply striated and almost black in colour, with the 



