THYRIDIDAE OF AFRICA AND ITS ISLANDS 95 



vertex. Patagia and prothorax brown, rest of thorax white. Hind tibia with outer spur of 

 distal pair slightly less than 1/2 length of inner spur. Fore wing, pattern as in PL 9, figs 37, 38; 

 PI. 2, E, F, translucent white with brown costa and pinkish red suffusion to wing margins and 

 brown transverse striations. Black spots between veins subterminally. Veins i? 4 and R s 

 joined, or R 2 -R$ from cell. Underside, as upperside. Hind wings, colour and pattern as fore 

 wing. Sc+R 1 and Rs free. 



Genitalia q" (PI- 34. n g s 186-188). Uncus simple, small patch of enlarged scales at base. 

 Gnathus with hooked tip. Juxta, two small rounded lobes. Basal process very small. Valves 

 simple. Aedeagus with spiny manica and larger group of spines in vesica. 



$. Wing, ii-5-i8'5 mm. Colour and pattern as male. Labial palps with third segment 

 equal in length to second segment, reaching above vertex. 



Genitalia $ (PI. 56, figs 334-338). Anal papillae short. "V"-shaped ostium, short sclero- 

 tized part to duct, wider posterior portion then broad duct covered with minute spines. Signum 

 variable in shape (PI. 56, figs 335-338), usually stellate and covered with spines. 



Discussion. This species is very variable in colour, size and pattern. In a 

 few examples the translucent white ground colour is heavily overlaid with a brown 

 reticulate pattern, in other specimens the reticulate pattern is much reduced with 

 only light transverse fasciae. In almost all the specimens examined the red colour 

 and the black subterminal spots on the fore and hind wings were clearly visible. No 

 geographical trends in distribution were apparent in the different colour patterns of 

 the specimens examined and very few specimens have sufficient data to consider the 

 effect of altitude, time of capture or other factors as possible factors causing the 

 colour variation found. Variation in specimens of this species was not only in 

 pattern and colour but also in some other morphological features. In twelve males 

 (Group B, below), the antennae do not have any pectinations while all the other 

 males (Group A, below) the antennae are strongly pectinate. Although there is 

 some variation in antennal pectination length in Group A, none of them have antennae 

 like Group B specimens. No other differences between these two groups of males 

 was found, the genitalia in the two groups are indistinguishable. Some of the 

 specimens with different antennal structures were from the same localities and had 

 apparently been collected together. No comparable difference was found in the 

 females. In Madagascar, the closely allied species, R. (Isothauma) opalinula 

 Mabille, has the simple (Group B) antennal structure. The Madagascan species is as 

 variable in colour and pattern as the African species but does not apparently have the 

 two antennal forms. The main difference between the Madagascan and African 

 species is in the number and size of the cornuti in the aedeagus of the male. In serrati- 

 comis the cornuti are numerous and spine-like but in opalinula they are short and 

 there are fewer of them. There are also other small differences in the median basal 

 process on the valve but some overlap of these differences occurs. In the female the 

 signum in the bursa of serraticornis is generally rounded, in opalinula it is elongate. 



The significance of the differences in the antennae of this species is not understood. 

 A detailed study of the micromorphological structures on the antennae was under- 

 taken, using the Scanning Electron Microscope. The structure of the antennae of 

 both Groups A and B was similar and some of these structures are shown in PL 25, 

 figs 131-133. Apparently the difference is one of growth of the length of the 

 pectination but does not seem to be correlated with the size of the insect. 



In the females of serraticornis there is some variation in the shape of the signum 



