THYRIDIDAE OF AFRICA AND ITS ISLANDS 19 



the abundance of the Thyridids in relation to other Lepidoptera. From a study of 

 these collections it is apparent that the Thyridids are not as abundant as some 

 families in collections of Lepidoptera in Africa and that frequently only one or two 

 specimens are collected at any one time. 



Since we know little about the biology of the Thyridids, it is possible that their 

 habits are different from those of other Lepidoptera but the few observations avail- 

 able do not suggest that this is likely, for example, they have been collected in 

 mercury vapour light traps. We are thus left with the impression that the number 

 of individuals of each species of Thyridid (with a few exceptions) are small in com- 

 parison with those of other lepidopterous families. This is confirmed by field 

 observations (e. g. Carcasson, personal communication). 



The remaining discussion on the distribution of the species must be read with 

 all these qualifications (ecology, collectors and lack of general data) in mind. 



At present the most northerly point at which species have been collected on the 

 mainland of Africa is on the west coast where several species reach almost i5°N. 

 On the drier east coast, they do not extend beyond 10 °N, but in the Nile valley, one 

 species (H. curvifluus) has been collected up to I2°N. On the whole it seems that the 

 Thyridids are absent from drier regions. 



No Thyridids are known from Africa north of the Sahara although several species 

 occur in other parts of the Palaearctic region. These species are known from south 

 Spain and Corsica but appear not to have crossed the Mediterranean into North 

 Africa. Parts of North Africa are reasonably well collected and it is surprising that 

 no Thyridids have been taken; however, it may again be that North Africa is an 

 unsuitable area for them. This pattern of distribution is similar to that in other 

 groups of animals (Butterflies, Carcasson, 1964; Birds, Moreau, 1966). 



From the distribution maps (1-73) several patterns of distribution are apparent. 

 The commonest type of distribution pattern (e.g. Map 62) is one which follows the 

 rain-forest zone of the west, either in the woodlands (and grasslands) around the 

 actual rain-forest or within the rain-forest itself. Other patterns of distribution 

 shown by maps 29 and 48 are where the species is restricted to the east coast or the 

 Rift Valley. As more collecting is done through Africa, these patterns will tend to 

 become clearer and with collection of some ecological data a comparison with the 

 vegetation will be possible. 



In one species, Cecidothyris pexa Hampson (p. 177), not only are more specimens 

 available than is the case with most species but also host records for the larvae are 

 available. The distribution of this species is shown on map 73 where it is super- 

 imposed on to the vegetation zones. C. pexa is separated into two subspecies, C. 

 pexa pexa Hampson and C. pexa guttulata Aurivillius (p. 179). At the extremes of 

 their range these two subspecies are very distinct externally, but where they overlap 

 in southern Central Africa, these differences break down and intermediates occur. 



The larvae of C. pexa produce galls (PI. 23, fig. 126) on species of Terminalia 

 (Combretaceae) . C. pexa pexa produces galls on the stems of Terminalia sericea 

 Burch, a shrub or small tree 3-12 metres high. T. sericea has a scattered distribution 

 over Southern and Eastern Africa (Griffith, 1959) and the distribution of C. pexa pexa 

 broadly follows it. 



