40 THE entomologist's record. 



Scents of Insects and their Meanings. 



By A. W. BACOT, F.E.S. 



Dr. Chapman's interesting note [Entomologist' s Record, xvii., pp. 

 321-322) on " Scents of Insects and some thoughts about their possible 

 meanings," reminds me of my failures when attempting to cross 

 Amphidasys strataria and A. betularia. These, I think, suggest that there 

 may be more openings for sexual selection among the assembling 

 Heterocera than is usually thought to be the case. 



My attempts to obtain fertile ova extended over three seasons, 

 beginning with numerous attempts in which the moths were placed 

 in large cages both indoors and out, but these never produced a single 

 pairing, chiefly, 1 fancy, because the males did not have room for a 

 sufficiently extended flight, but partly, at any rate, owing to the restless- 

 ness of the females. At the same time it was possible, under these 

 same conditions, to get as many pairings between individuals of the 

 same species as desired. 



In the woods I was twice successful in obtaining pairings between 

 wild males of A. strataria and females of A. betularia var. douhledayaria. 

 On the occasion of the first success I saw the strataria enter the open 

 compartment of the cage in which the female A. betularia was situated, 

 and pairing took place almost immediately without any hesitation on 

 the part of either moth. At the second successful attempt the female 

 A. doubledayaria was resting on the outside of the cage in which the 

 females of A. strataria were confined. I did not see the pairing take 

 place but the female had not apparently shifted from her calling 

 position. 



Both these females had been out some eight or ten days before 

 pairing took place, but the pairings were apparently quite normal in 

 that the pairs in both instances were carried home by cycle a distance 

 of ten to fifteen miles without disturbing the moths, and on the 

 second occasion the pair was shifted from the cage into a box without 

 their separating. In both instances, the nights were unfavourable 

 ones for assembling, and very few males flew up. With one single 

 exception the ova of both pairings were infertile. But the disappoint- 

 ing though favourable nights, on which the males flew up freely but 

 would not or could not pair, afi'ord the best evidence which bears on 

 the males' possible selection of partners. 



On one occasion, when the wind blew almost a gale and there was an 

 abnormally high temperature (I think 60°F.) a single male dashed up, 

 went into the cage, buzzed round for a few moments, and then retired 

 not to return ; an unusual circumstance possibly due to the strength 

 of the wind. Upon a decidedly favourable night with a slight 

 breeze, some eight or ten males flew up and several entered the cage, 

 but, although they flew round and fluttered close to, even touching, the 

 females of betularia, they made no attempts to pair during my observa- 

 tion, and no pairings took place. Other unsuccessful attempts were 

 made, but my memory is not clear as to what happened, probably 

 they were mostly occasions on which no moths assembled at all. My 

 only attempt in 1905 was made on a calm, almost windless, and some- 

 what chilly, night, only one male flew up and his attempts to pair were 

 most persistent, on three separate occasions I saw him attempt 

 copulation, and each time the female A. doubledayaria avoided him. 



