1892.] 



THE BRITISH NATURALIST. 



in the males of which the antennae are often four times the length of 

 body, while those of the female are not more than half those of their 

 partners. In a few instances the number of joints varies in the two 

 sexes, thus : the males of Pvioiius coriarhis, Molorchus minor, and 

 Nacerdes melanura have the antennas 12-jointed while those of the 

 females have only the usual number -11; and in Holopavamecus 

 depresstis, according to Fowler, the female has 10 joints in the antennae 

 while the male has only g. Pria dulcamara' has the club of the male 

 antennae composed of 4 joints, while that of the female has only 3, a 

 fact which caused Stevens to place the sexes in separate genera. 

 The club of the antennae is not only much longer in the male 

 Meloloiitha but is composed of 7 lamellae while that of the female has 

 6 only. In the following species, also we find the club of the antennae 

 longer in the male : Serica bmnnea, Rhizotrogiis, Throsciis dennestoides, 

 &c.; Helocerus claviger and Megatoma undata ; while the male of 

 Attogeims 2)Mio has the last joint of the club as long as the whole of 

 the other joints together, the female having this joint equal to the two 

 preceding together. Tiresias serra has the club of the male much 

 larger than that of the female and also strongly serrate. The male 

 of EuconmLS denticomis has two joints of the antennal club distinctly 

 widened and sharply toothed on the inner side, that of the female 

 being simple. Many beetles have the antennae of the male with the 

 joints so extended as to produce an appearance like that of the teeth 

 of a saw (serrate) or of a comb (pectinate) while the females have 

 these organs either quite plain, or only slightly serrate. Instances of 

 such are common among the Elateridae— Corymhites pectinicornis and 

 cupveus and Microvhagus pygmceiis being examples from this group. 

 The same condition is observed in Prionocyplion serricornis, Tillus 

 elongates, Xyletimis ater, Prionus coriarius, Bfiichns pectinicornis, 

 Pyrochroa pectinicornis, &c. Instances of still greater development of 

 the male antennae are furnished by the fan-shaped (flabellate) 

 structure of these organs in : Melasis huprestoides and Ptilinus 

 pectinicornis — in the females of both of which these organs are simply 

 pectinate, Drilns flavescens; the male of which has most remarkable 

 fan-like antennae while those of the larviform female are short and 

 thread-like. The antennae reach their greatest development among 

 British beetles in the males of the curious Metcvcus paradoxus which is 

 parasitic on wasps, in which these organs are strongly comb-like on 

 two sides— like a feather, those of the female being slightly serrate on 

 one side only. Most singularly in Hyleccetns — in which the male has 

 the fan-likc palpi, this sex has the antennae feebly serrate, while in 

 the female they are strongly serrate or even comb-like — strange 

 exception to the usual condition. Occasionally we meet with 

 instances where only one, or a few only of the antennae joints undergo 



