284 Insecta. 



of the bursa copulatrix: the form of this plate is usually specifically constant, 

 and in some cases it can be used to "confirm or modify views based on that of 

 the male organ" (p. 16). On the other hand, certain other characters are subject 

 to remarkable Variation within the limits of the genus, or sometimes of a Single 

 species. E. g., in the c? the tarsal claws of the 2^*^ and 3'''* pairs of legs are 

 usually unequal, one being long and curved, the other short and bent down, but 

 in a few species they are equal and similar, like those of the '^: one species, 

 Ä. servona, has normally equal claAvs, but occasionally specimens with unequal 

 claws are found. Many species exhibit transparency of the wing, which is attained 

 (I) by reduction in width of the scales, (II) by the scales being represented by 

 hairs, (III) by the scales being normal in form but reduced in number, (IV) by 

 the scales being normal in form but raised, so that light can pass between them, 

 (V) by the scales being absent. The genus is almost confined to the Ethiopian 

 Region, from which 133 species are enumerated: 4 or 5 occur in the Oriental 

 Region. 



The larvae of Acraea are gregarious. The imagos are slow of flight: some 

 species frequent open country, others forests, and a few frequent marshy land. 

 They have been observed to fight desperately for the possession of a particular 

 leaf on which to deposit their eggs. They are extremely tenacious of life, their 

 chitinous integuments being very tough, and the insects very resistant to the 

 action of poisons. Many emit an acrid juice when injured. Experiments on some 

 species tend to show that they are very distasteful to insectivorous creatures. 



In courtship, the c? seizes the 5 in the air. After copulation the 5 of many 

 species bears on the underside of the body a mass of hard wax-like material (the 

 "sphragis" or "seal"), formed by a secretion from the body of the cf : it frequently 

 contains hairs and scales from the body of the J". Its purpose appears to be to 

 prevent copulation being repeated with other J'c?. It may also possibly prevent the 

 further Omission of an alluring scent by the $. There is no correlation between 

 the occurrence of the "sphragis" in the $ and the inequality of the d" tarsal 

 claws: this latter phenomenon is unexplained. 



"Seasonal dimorphism" is exhibited to a greater or less extent by many 

 species. Several examples are given (pp. 10 — 12), in some of which the occur- 

 rence of the "wet-" and "dry-season forms" corresponds well with the seasons. 

 "Sexual dimorphism" is very common, a marked difference in the appearance 

 of cT and $ being the rule. Also, either the J', or the ?, or both sexes, may be 

 Polymorphie. In A. terpsicJiore the $ is extremely Polymorphie, the d" rather less 

 so; the different forms of c? and $ do not appear to be definitely associated 

 with one another, and the condition appears to be merely one of great in- 

 stability. In other cases the different forms may be definitely associated with 

 one another, or their occurrence may be governed by geographical conditions, 

 or the different forms of $ may be mimetically associated with species of other 

 genera (l'lanema, etc.). In A. Jycoa both d" and $ are Polymorphie, each exhibi- 

 ting a series of forms which are associated with one another in different parts 

 of the ränge, while throughout the series the sexes are distinguished by a con- 

 stant difference in colour of the forewing-spots. Several interesting insular species 

 and races occur, not only in Islands such as Sao Thome and the Comoros; even 

 two small Islands in Lake Bangweolo have furnished distinct forms of certain 

 species (p. 14). A general correspondence of colour with geogi'aphical distribution 

 is sometimes seen: e. g., A. zeAes, egina and nafalica have forms with dark fore- 

 wings in the extreme West of Africa, while the red colour increases in extent 

 as the species ränge East and South. The Variation is extremely complicated, 



