imperfectly-himon South African Zepidcyptera. 391 



clearly that the case is one of seasonal dimorphism, quite 

 akin to those presented by many species of the Pierine 

 genus Teracohts in the same regions, in which the con- 

 spicuous white or whitish underside of the hindwings 

 during the wet season is replaced during the dry season 

 by one more or less obscured with paler or deeper tints of 

 reddish-ochreous or even brownish-ochreous. 



I have not hitherto found recorded any other instance 

 of seasonal modification in the species of Pyrgns, either in 

 Africa or elsewhere ; but — considering how large a genus 

 this is, how very widely dispersed over the tropical and 

 temperate regions of the globe, and how many of its forms 

 are so variable and so closely allied as to be with difficulty 

 distinguishable — it seems by no means improbable that 

 " dry " and " wet " phases are not rare among them, but 

 until now have been mistakenly regarded as distinct 

 species. The phenomenon has indeed been recognised as 

 occurring among some species of other genera of the 

 Hesjjerunae ; Mr. Neave mentioning (I.e. pp. 68 and 71) 

 specially two cases in N. Rhodesia which came under his 

 notice, rid. those of Eagris jamesoni, E. M. Sharpe, and 

 Abantis venosa, Trim. The latter instance is closely com- 

 parable with that of Pyrgus secessns, for Mr. Neave writes 

 of this species of Abantis : " Extreme dry specimens are 

 of a golden-brown colour, losing all the white discal area 

 and black margin of the hindwing underside." 



Fam. SPHINGIDAE. 



Sub-fam. Smerinthinae. 



Platysphinv hourkei, Trim. 



Platysphhix hourkei, Trim., Ent. M. Mag. (2), xxi, p. 209 

 (1910). 



Plate XVII, fig. 7 (?). 



I take this opportunity of giving a figure of the only 

 example (a $) known to me of this very striking Smerin- 

 thine hawkmoth, which was taken in Zululand in 1909 by 

 my friend Rear- Admiral Edmund Bourke, as noted in my 

 description above cited. In pointing out the relation of this 

 form to the Los Islands P. phyllis, Rothsch. and Jord., and 

 the larger Congo P. stigmatica, Mab.,I omitted to mention 

 that a specimen of the latter species, taken on grass near 



TRANS. ENT. SOC. LOND. 1912. — PART II. (oCT.) DD 



