90 



DIETRICH SCHNEIDER 



of impulses to stimuli such as cycloheptanon and fatty acids with 3 and 4 

 C-atoms (Fig. 4). 



10 



12 



14 



16 



Id 



20 C 



3 4 6 6 



Fig, 4, Relationship of receptor potential (GP) amplitude to chain length (C) 

 of unbranched fatty acids in Necrophoms humator. Points on negative side of 

 ordinate represent different degrees of hyperpolarization (from Boeckh, 1962). 



RECEPTORS FOR ODOROUS SEX ATTRACTANTS 



Odour stimuli not only lead many insects to food or prey but serve as 

 signals for sexual reactions. Best known in this respect are the sexual 

 attracting substances of the silkworm moth Bombyx mori and the gypsy 

 moth Porthetria dispar. The lure substances of these species, as well as 

 those of other moths, are produced by glands located in the intersegmental 

 folds near the abdominal tip of the female. Intensive work by two groups 

 of biochemists has clarified the chemical nature of the lure substances. 



In Bombyx the substance has been chemically identified as hexadecadien- 

 \0-trans, 12-c/5-ol-(l) (Table 1a) and is called Bombykol (Butenandt, 

 Beckmann, Stamm and Hecker, 1959 ; Hecker, 1960 ; Butenandt, Hecker, 

 Hopp and Koch, 1961 ; Butenandt, Beckmann and Hecker, 1961 ; Bute- 

 nandt and Hecker, 1961) ; in the gypsy moth the substance has been 

 chemically identified (Table 1b) as ^+^ 10-acetoxy-r/5-7-hexadecen-l-ol 

 (Jacobson, Beroza and Jones, 1960 ; Jacobson, 1960 ; Jacobson, Beroza 

 and Jones, 1961). 



Behavioural bioassays for the identification of Bombykol (cf. Butenandt, 

 1955 ; Hecker, 1960 ; Butenandt and Hecker, 1961) demonstrated a very 

 low reaction threshold of Bombyx males to the species lure substance. If a 

 glass rod is dipped into solvent containing only 10'^V//g/ml of attractant 

 and held in front of the males, at least 50 per cent react with typical move- 

 ments. The other three geometrical isomers of the alcohol are much less 

 effective (Table 1). Typical for the Bombyx reaction is the fact that prac- 

 tically all male moths respond within a few decadic concentration steps 



