African S/iecies of Erotylidae. 141 



sexual dimorphism of some at least of the species. The 

 males are characterised by greatly dilated tarsi ; but^ in 

 several species, they have a more remarkable peculiarity 

 in a conspicuous opaque area upon the posterior part of the 

 elytra. Analogy would lead us to consider this distinctive 

 of the females, as in Water-beetles, various Lamellicornia, 

 and other groups in which a similar phenomenon occurs ; 

 but this is not the case. The dilated tarsi are not by them- 

 selves sufficient to determine the sex, for, although almost 

 invariably indicative of the male, in certain genera of 

 Languriinae, a closely related group, it is the female in which 

 the tarsi are most dilated. In these and other cases the 

 determination of the sex from external indications only has 

 led to totally wrong conclusions, and dissection is essential 

 to absolute certainty. 



As is frequently ibund with secondary sexual characters, 

 the opaque dorsal area is not found in all the species of the 

 geuus. I have found it in three, in one only of which 

 (P. andrece, Crotch) both sexes are known, but in all it is 

 confined to male specimens. In P. coccinelloides, Crotch, 

 P. dorsalis, Gorh., and P. bizonatus, sp. n,, both sexes are 

 equally smooth. Although it has not hitherto been recorded, 

 this curious phenomenon is also found in the genus Neo- 

 triplax — in a strongly marked form in iV. atrata, Lewis, and 

 to a less extent in N. lewisi, Crotch, both Japanese species. 



Daaie [Engls) cequinoctialis, Thoms., is almost certainly 

 the species later described by Crotch as D. capensis, which 

 has an exceedingly wide range in Africa. 



The only known African representatives of the Encaustes 

 group are here described. Gorham described in 1883 

 a species, Micrencaustes torquata, the habitat of which 

 he stated to be Old Calabar ; but in 1901 he expressed 

 himself doubtful of its African origin. In the British 

 Museum there is a specimen of this species, derived, like 

 Gorham's type, from Andrew Murray's collection, and 

 labelled "]Malay Peninsula.'^ 



The true systematic position of this group has never been 

 recognized. The monographer of the Erotylidse, Lacordaire, 

 in his Synopsis of the genera, divided them into two series, 

 at the head of each of which he placed an isolated genus as 

 to the actual affinities of which he was evidently uncertani. 

 The first of these, Encaustes, on account of its large size and 

 elongate shape, is, not unnaturally, generally associated 

 with the other large Old World species represented by tliose 

 now called by M. Bedel Mimodacne ; but Chapuis has 

 pointed out that Lacordaire, in adopting this view, was 



