Effect of wasp size, physiological state, and prior host experience on host-searching behavior in a parasitoid wasp (Hymenoptera: Ichneumonidae)

Abstract

Host-searching behavior in insects generally varies among individuals. A number of physiological and environmental factors can be involved in such individual variation. Here, a series of behavioral observations were made to highlight the importance of physiological state (i.e., number of mature eggs a female carries, amount of nutrient reserves, etc.) and learning state (i.e., prior host experience) on host-approaching behavior of parasitoids. Itoplectis naranyae (Hymenoptera: Ichneumonidae), a solitary endoparasitoid wasp attacking lepidopteran pupae and prepupae, was used as a test insect. The results show that female wasps with experience ovipositing on hosts 2 days before the test found hosts more quickly than did naïve wasps. Prior experience of host odor itself did not affect host-finding behavior, however. A single oviposition was enough for wasps to shorten time to find a host; additional experience had no significant effect on the efficiency of searching. The number of mature eggs a female carried had no effect on the time required to find a host regardless of prior host experience. The size of wasps, instead, was a significant factor when wasps had no prior host experience, and larger wasps found hosts more rapidly than did smaller wasps. Searching activity was not affected by how many hosts a female wasp had fed on before testing.

Host Approaching Behavior in a Parasitoid Wasp (Hymenoptera: Ichneumonidae) as Influenced by Physiological State and Host Type

“…The colony was maintained on pupae of a laboratory host, Galleria mellonella (Lepidoptera: Pyralidae). The host was reared on an artificial diet [3,13]. Host cocoons containing fresh pupae were presented to female I. naranyae in plastic containers.…”

“…Egg load variation is shown to link to variation in the ovipositional decision of female parasitoids including I. naranyae [3,[8][9][10]15]. Thus, egg load influeces motivation to ovipposit.…”

“…The interpretation is that, regardless of the number of mature eggs available, females should examine the suitability of any hosts if they have once recognized the hosts could be of the highest quality. Test female I. naranyae had been allowed experience with fresh host cocoons before testing, and are likely to learn the host type as highly suitable [3]. Thus, learning enables test females to recognize the presence of a high quality host from a short distance.…”

“…It is however common that behavior of an insect species varies considerably among individuals, and much less attention has been paid to factors that cause variation in the behavior [1][2][3][4].…”

Advances and challenges in the identification of volatiles that mediate interactions among plants and arthropods

“…Indeed, it is well known that responses of insects to VOCs are highly plastic, depending on the physiological state of the animals and on previous experiences with odour sources. [187][188][189] Different forms of learning may modify the perception of chemical compounds and the response of insects towards odour sources. [190][191][192][193] This flexibility in the insects' responses, as well as the great variability in the odours produced 172,174,[194][195][196] duly complicates the elucidation of key attractants, and learning experiments should be included in behavioural assays.…”