ACTIVITY OF FEMALE BLOWFLIES, (PHORMIA REGINA), IN RESPONSE TO NOVEL ODOURS

Female blowflies (Phormla regina Meigen) which had been fed either sucrose (S flies) or sucrose and yeast (SY flies) were tested for their response to novel odours in an actograph. All responded with an increase in activity. S flies were consistently more responsive than SY flies both in their increase in activity and in the number of different odours to which they responded significantly. S flies found food rapidly over a short distance when they were made active either by a stimulating odour or by mechanical agitation. Olfaction, rather than vision, was demonstrated to be the sense mediating the increase in activity. In insects the consummatory aspects of feeding have been studied extensively, but the appetitive aspects are poorly understood. The sense of smell and the behaviours stimulated by odours play a fundamental role in the appetitive component of food finding. Pospisil (1958), for example, showed that Lucilia ceasar, a fly found on freshly killed meat, was attracted to low concentrations of skatol in a two-choice olfactometer, but repelled by high concentrations. On the other hand, Calliphora vomitoria and C. mortuorium, two flies found on very decayed meat, were attracted to the concentration of skatol which repelled L. ceasar. Ishikawa et al. (1969) Found that silkworm larvae could find mulberry leaves 10 cm away within 3 min, whereas antennectomized caterpillars were unable to find the leaves. The consummatory aspects of feeding are well known in Phormia regina (Dethier, 1976), so the present experiments were designed to explore the contribution of olfactory stimulation to the appetitive component. Two types of experiment were undertaken. In one the effect of food odours on activity levels was studied, and in the other the efficiency of this response in finding food over a short distance was examined. Previous studies (Rachman, 1980) showed that feeding behaviour was affected by the nutritional history of the flies, so female flies fed one of two diets were tested. RESUME ACTIVITE DE PHORMIA REGINA EN REPONSE DES ODEURS ETRANGES Des effluves de banane, pomme, fore de bœuf et levure ont ete testees en actographe contenant 20 femelles de Phormia regina de 2 a 9 jours. Ces mouches avaient ete nourries anterieurement, soit sur sucrose seul a 0,1 M (mouches S), soit sur sucrose (0,1 M) el 10% de levure (mouches SY). L'activite des mouches croit quand les odeurs sont introduites, mais il en est de meme quand le courant d'air pur est change. L'augmentation de l'activite provoquee par la banane, la pomme, et la levure est significativement superieure pour les mouches S, a celle provoquee par le changement du courant d'air (Fig, 1), Chez les mouches SY l'augmentation significative est observee avec la banane et la levure (Fig. 2). Les mouches S sont plus actives et repondent mieux que les mouches SY. Une goutte de levure dans un recipient avec des mouches S de 6 jours stimule leur activite et la goutte est trouvee rapidement (16 sec). Des gouttes d'eau ou de sucrose ne stimulent pas l'activite, et les mouches mettent beaucoup plus longtemps pour les trouver (> 100 sec.), En secouant les recipients pour rendre les mouches actives on obtient une decouverte des gouttes d'eau ou de sucrose aussi rapide que la decouverte des gouttes de levures par les mouches non perturbees. Des mouches antennotectomisees, non perturbees, mettent 252 sec, pour trouver une goutte de levure, mais des mouches antennotectomisees et agitees artificiellement trouvent les gouttes presqu'aussi rapidement que les mouches normales non perturbees (Fig. 3).