124 NOVITATKS ZOOLOGICAE XXIII. 1916. 



NOTES ON ARCTIIBAK 



By Db. KARL JORDAN. 



(With 47 Text-figures.) 



IN the taxonomy of species colour and pattern have played a more important part 

 in Lepidoptera than in other orders of insects. In many genera of Lepidoptera, 

 however, the pattern has remained so uniform or has become so simplified or so 

 unified that colour distinctions between the species are more or less absent, the 

 species being so similar to one another that they are not, or not easily, distinguished 

 without an investigation of their structure {congeneric sxjnchromatic species). On 

 the other hand, there are species and groups of species in which colour and 

 pattern, and often also the shape of the wings and the size, are so variable 

 individually that none of these external distinctions are trustworthy guides in 

 differentiating the species. These extremes offer a most interesting field for 

 research. They not only have many surprises in store for the systematist, but also 

 are of considerable importance for the study of the wider question of evolution. 



Instances of both these extremes are not rare among the Arctiidae, and Lord 

 Rothschild has drawn my attention to qnite a number of species which he thought 

 might possibly be composite. In offering herewith some notes on a few American 

 congeneric synchromatic Arctiids I confine my remarks in the body of the paper 

 almost exclusively to the systematics of the species with which I am dealing, but 

 venture to mention at the end of the paper a few points of general interest of which 

 the Arctiids here described may be regarded as illustrations. 



Genus Ammalo Walk. (1855) 



In Hampson, Lep. Phal. iii. p. 83 (1901), the genus Ammalo contains six 

 species, one of which is insulata Walk. (1855). This is a small species (length of 

 forewing 13 to 22 mm.), with a buff-yellow abdomen which bears black dorsal and 

 lateral spots or dots, the thorax and wings varying from cream-colour to buff-yellow, 

 and the antennae, palpi, lower part of the frons and the tibiae and tarsi being more 

 or less blackish brown. It is a very uniformly coloured insect. 



An examination of the specimens in the Tring Museum (about 150) and of the 

 series in the British Museum has produced convincing evidence that there are three 

 such yellow species instead of one. Apart from one of them having the frons 

 rather more extended blackish brown than the others (the difference being measur- 

 able under a lens), these species are alike in colour, but perfectly distinct in 

 structure in both sexes. 



The species commonest in collections is 



1. Ammalo insulata Walk. (1855) 



Originally described from Jamaica, this species is known also from the other 

 larger West Indian islands as well as the Bahamas, Grand Cayman, Grenada and 

 Florida, and probably occurs on most of the islands ; on the continent it is found 

 from Mexico to Colombia, its range extending eastwards to British Guiana, and 



