LABORATORY STUDIES ON BEHAVIORAL INTERACTIONS OF PROSTEPHANUS-TRUNCATUS (HORN) (COLEOPTERA, BOSTRICHIDAE) WITH CONSPECIFICS, SYNTHETIC PHEROMONE AND THE PREDATOR TERETRIOSOMA-NIGRESCENS (LEWES) (COLEOPTERA, HISTERIDAE)

A bioassay method was devised to test the responses of adult Prostepha nus truncatus (Horn) to conspecific adults or synthetic pheromone and Co observe the response of the predator Teretriosoma nigrescens (Lewes ) to adult or larval P. truncatus or the synthetic pheromone of this s pecies, The results confirmed earlier observations that male P, trunca tus are the source of a pheromone attractive to both males and females , P. truncatus adults (in this case virgin females) are disinclined to leave food in response to the pheromone and maize itself is relativel y unattractive to P. truncatus. For the first time it has been demonst rated that males are not attracted to females, females repel or avoid each other and males are less attracted to the naturally produced pher omone secretion than are females, In view of the fact that unmated fem ales will not leave food to locate a calling male it was concluded tha t the female response to the pheromone is primarily a means of locatin g a food source, rather than a sexual partner, In contrast, males rele ase their secretion to attract females, When adult P, truncatus were t ested against grains treated with the synthetic pheromone the response of males and females was apparently identical, in contrast to the low er response of males when tested against conspecific males. It seems p robable that the amounts of pheromone used when testing the synthetic mixture are greater than would be produced naturally by a calling male and that this may mask the apparently lower sensitivity of males to t he natural pheromone. The pheromone of P. truncatus is known to be a k airomone for T. nigrescens, but in the bioassay this species was not a ttracted to synthetic pheromone and responded more strongly to empty m aize grains than to adult or larval P. truncatus. It would appear that when walking, adult T. nigrescens are unwilling to approach closely t o P. truncatus. The possible significance of this is discussed. (C) 19 98 Elsevier Science Ltd. All rights reserved.