Determination of the larval feeding indices of Hyles euphorbiae (Lep.: Sphingidae) on different species of weedy spurges

The larvae of Hyles euphorbiae (L.) are monophagous and feed on the succulent species of the genus Euphorbia. Obtaining more information on the feeding rate and preferred host plants of the larvae of H. euphorbiae could be useful in biological control programs. In this research, the larval feeding indices of this species i.e. consumption index (CI), approximate digestibility (AD), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were determined on the five most prevalent species of the genus Euphorbia (E. macroclada, E. denticulata, E. seguieriana, E. heteradena and E. boissieriana) in the fields and rangelands of West Azerbaijan in laboratory at 19 ± 1ºC, 65 ± 5% RH and a photoperiod of 14: 10 (L: D). The experiments were conducted during larval period of the moth (four larval groups and each group containing eight larvae) inside colorless plastic containers. The results indicated that the larval feeding rate on the above mentioned Euphorbia species were not significantly different (P > 0.05). The maximum (24.97 ± 0.71 g) and minimum (21.24 ± 0.88 g) rates of larval feeding were on E. macroclada and E. boissieriana, respectively. The mean weight of feces that excreted by rearing larvae on E. boissieriana (11.20 ± 0.73) was significantly (P < 0.05) lower than that of other Euphorbia species. The comparison of the mean weight in the late larval stage on five Euphorbia species was not significantly different (P > 0.05). Mean efficiency of conversion of ingested food on E. boissieriana (0.200 ± 0.01) was more than the other Euphorbia species, though the difference was not significant. It could be concluded that the entire Euphorbia species tested are the host plant of H. euphorbiae and larvae of H. euphorbiae for reaching to normal weight increase the efficiency of conversion of ingested food and decrease the feces and its excretion. This moth is a suitable agent for using in biological control programs of the Euphorbia weeds.