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1 2 . 2 E 1, cos2 CY and I z , z = I z sin2 a. the observed depolarization Pu,m is given by

In Rhodnius, a volatile substance produced by mating pairs is attractive to male insects. The pheromone acts also as a sexual stimulant; males respond in the absence of females by attempting copulation with other males. Air swept over mating pairs and conducted to a cage at a considerable distance proved to be highly attractive to males. Proximity of the sexes, without opportunity for actual contact, does not stimulate production of the pheromone. Since males and females will copulate only after a blood meal, feeding is a prerequisite to pheromone production. Also, unfed males will not respond to the attractant. Males of this nocturnal species were stimulated only in complete darkness.

Chymopapain is a polypeptide of 218 amino acid residues. It has considerable structural similarity with papain and papaya proteinase omega, including conservation of the catalytic site and of the disulphide bonding. Chymopapain is like papaya proteinase omega in carrying four extra residues between papain positions 168 and 169, but differs from both papaya proteinases in the composition of its S2 subsite, as well as in having a second thiol group, Cys-117. Some evidence for the amino acid sequence of chymopapain has been deposited as Supplementary Publication SUP 50153 (12 pages) at the British Library Document Supply Centre, Boston Spa., Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained on the terms indicated in Biochem. J. (1990) 265, 5. The information comprises Supplement Tables 1-4, which contain, in order, amino acid compositions of peptides from tryptic, peptic, CNBr and mild acid cleavages, Supplement Fig. 1, showing re-fractionation of selected peaks from Fig. 2 of the main paper. Supplement Fig. 2, showing cation-exchange chromatography of the earliest-eluted peak of Fig. 3 of the main paper, Supplement Fig. 3, showing reverse-phase h.p.l.c. of the later-eluted peak from Fig. 3 of the main paper, and Supplement Fig. 4, showing the separation of peptides after mild acid hydrolysis of CNBr-cleavage fragment CB3.

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