Case Study Learning in the Parasitoid Wasp (Hyssopus pallidus)

 Cydia pomonella is the major pest of apple fruits. Parasitoid adult disperse throughout the orchard to find new host.  Hyssopus pallidus (parasitoid) used as biocontrol to control the pest.

Before discuss this case study We should know, A parasitoid’s host-searching ability depends on, i.Responses to chemical cues. ii.These responses have both genetic and learned components.  Any critical phase at which a parasitoid is more likely to learned?  Does learning carry through from one life stage to another? ? Questions arise in this topic are

Moth Caterpillars (1 st instar moth) Apple Feed Extract Worm Waited for 5 th instar Worm Filter paper with extract Apple piece Apple Extract Feed on wheat germ Introduced mated female in each group New cage without apple cues New Generation Q. Did parasitoid need to learn fruit related chemicals from caterpillars and their feces or exposure to fruit itself was sufficient?

New Generation 4 days old Filter paper on top treating with apple extract Hyssopus larva fed with apple diet showed significantly greater response to host frass than reared without apple cues.

Q. Did a high response to host frass require exposure to both the taste and smell of apple? Apple supplement Odor of apple extract Both treatments enhanced female response but their response towards olfaction was more effective as taste and smell together. Parasitoids reared on caterpillars

Q. Was their a sensitive stage in parasitoid’s life history for learning the relevant stimuli? Wasps exposed to apple clues at different developmental stags. Never exposed to apple at all Group 1 Showed greater response as adult to natural frass. Exposed to apple throughout its life Group 1 Group 2

Stage exposed to odour of apple fruit extract Adult response to frass extract from apple-fed host caterpillars Total development Egg-young larva Old larva-pupa Pupa emergence Adult No Exposure (Control) (0) Response(s) Days from oviposition

Parasitoids are more responsive to the control than menthol Control Group Parasitoid used only solvent Egg to Larvae Experimental Group Parasitoid used Menthol Q. Was pre-imaginal learning confined to fruit cues, or was it a more general phenomenon?

Parasitic wasp Hyssopus pallidus learns to locate its hidden host by its frass and this recognition is two stage process.  Host-derived chemicals in frass innately.  Apple derived chemicals learned only through exposure in early life cycle; not early adulthood, but from egg to larva