32 [February, 



In this respect the conditions of lOOG were much nearer than 

 those of 1904 to those Milliere describes ; he found his larvae appa- 

 rently altogether in the flowering stems. 



These differences in the larval habits had one other very curious 

 result. The parasites affecting the larvae in 1904 were confined to 

 Xanthandrus comtus. Of this fly I had more than a score against 56 

 imagines of //. liyerana. The Sicilian larvae produced Tachinid and 

 Hymenopterous parasites and no X. comtus, though that fly existed 

 there. 



In 1906, instead of X. comtus being in number about one to three 

 of the bred moths, only four or fi.ve larvae were met with, although 

 several hundred moths were bred. The liyerana larvae were not 

 sufficiently gregarious to attract, or if attracted to permit of the 

 rearing of the fly. On the other hand several Tachinid flies emerged 

 as well as two Hymenopterous parasites, all of common species of 

 omnivorous habits. 



That X. comtus could not thrive on more or less solitary larvae is 

 obvious, but why should these be moi^e readil}^ found by Tachinids 

 and Ichneumons ? Possibly a plant capable of entertaining a number 

 of larvae also enabled them to hide more deeply. 



Without attaching much importance to, or expecting any serious 

 result from, the procedure, it occurred to me to keep separate the 

 larvae of R. liyerana collected from two localities at Hyeres. These 

 localities happen to be almost exactly three miles apart, and have 

 belween them in any moderately direct route a gap of at least a mile 

 and a half absolutely without Asphodel. The result, however, was 

 very remarkable, and is the first definite fact offering the possibility 

 of a clue to the significance of melanism in the moth. 



From the one locality the dark specimens were only 14 per cent, 

 of the moths bred, in the other 48 per cent. There were a sufiicient 

 number of moths bred to make these figures thoroughly trustworthy. 

 In the one case 169 moths with 23 dark specimens, and in the other 

 246 moths with 1L7 dark ones. 



In the first set were five ab. marginula, in the second only one. 

 If these be called dark ones, then the percentage would be 17 per 

 cent, and 48 per cent, (in round figures). 



The first locality with few dark specimens was " La Plage," the 

 sea shore opposite Hyeres ; the second with many dark specimens was 

 the " Maurettes," the low hills behind Hyeres. 



The interval separating the two localities, together with the 



