724 Dr. T. A. Chapman on 



comprehending how the three forms preserve their distinct- 

 ness. It is, in fact, simply a case of segregation. Both 

 species of Hderogynis are limited in their powers of 

 dispersal by the female laying her eggs in her cocoon. 

 All travelling from one area to another must be done by 

 the larva. They are here in quite the same conditions as 

 other species with apterous females. In most species with 

 apterous females dispersal by larval migration is facilitated 

 by a certain amount of polyphagous disposition on the 

 part of tlic larva, this is certainly the case in Orgyia and 

 in many Psychids. Even so, however, dispersal must be 

 a slow process, and so far as such dispersal is concerned, 

 it is quite conceivable that there might easily be enough 

 separation of portions of the species even in continuous 

 areas, to permit of distinct races arising. A further check 

 to this, however, results from the male moth being usually 

 very active and capable of flying considerable distances. 

 Crossing thus readily takes place between colonies at 

 considerable distances and imposes a serious impediment 

 to any distinctive variation between them. In most years, 

 a majority of adjacent colonies would thus be crossed with 

 each other, and the result at the end of a few years would 

 be that all colonies within a large area would be crossed 

 with each other mediately if not immediately. 



Considering the rather wide area of the range of H. 

 jjcnella, it probably, like so many other insects, has local 

 races and varieties. But in the smaller regions within 

 which I knew it, ranging from an elevation of 2000 feet 

 at Digne to 8000 at Lauteret, and from Grenoble nearly to 

 the Mediterranean, I am aware of the existence of no local 

 variation at all comparable to that of H. 2>aradoxa which 

 I am describing. The almost polyphagous larva renders 

 it capable of traversing, slowly of course, practically the 

 whole of this area, and the male is I think more adventur- 

 ous than that of //. 'jiciradoxa. 



H. i^arculoxu is very differently conditioned ; the larva 

 is confined to a few food-plants. It is not like 2^cnclla, 

 j^olyphagous under some circumstances, nor even like it 

 pleased with almost any leguminous plant. It must have 

 broom, and not any broom. Out of six or seven plants 

 that I called broom, Cytisns or Genista, and several other 

 plants of the same and allied genera, it would eat only 

 three, and one of these only as a substitute. There are 

 possibly other brooms growing elsewhere in Spain that 



