Evidence that the factor used by the tapeworm, Hymenolepis diminuta, to direct the foraging of its intermediate host, Tribolium confusum, is a volatile attractant

We have previously demonstrated that flour beetles, Tribolium confusum, are more attracted to the feces from rats with patent Hymenolepis diminuta inf ections than to feces from uninfected rats. The objective of this study was to determine if this effect is due to a volatile attractant. Volatile subs tances emitted by feces from H. diminuta-infected rats or from uninfected c ontrols were collected by aspirating fresh rat feces, while trapping the vo latiles on Porapak Q (a solid adsorbant). The volatiles were eluted from th e Porapak Q with diethyl ether, and the relative attractancy of the volatil es to prestarved beetles was assessed by bioassay. More beetles were attrac ted to volatiles of feces from infected rats than to volatiles of feces fro m uninfected controls (P less than or equal to 0.0001). The magnitude of th e response varied with the time in the bioassay test arena and also the con centration of the volatiles (P less than or equal to 0.0232). When the vola tiles were concentrated by aspirating more boli over a longer period of tim e, the beetles responded more quickly and in greater numbers to the volatil es of feces from infected rats. The experiments presented here provide the first indication that a tapeworm (H. diminuta) can enhance its chances of t ransmission by directing the foraging of its intermediate host (T. confusum ) through the use of attractive, volatile material released from the feces of its definitive host.