Abstract
Papilionid butterflies of the tribe Troidini are specialists on plants of the family Aristolochiaceae. The role of plant volatiles in host recognition by adult and larval stages of these insects remains unknown. We used Battus polydamas archidamas (Papilionidae: Troidini) and its host-plant, Aristolochia chilensis (Aristolochiaceae), to study: (i) the olfactory and electrophysiological responses of adults to headspace volatiles of the host-plant, (ii) the chemical composition of the headspace volatiles of the host-plant, (iii) the patterns of aggregation of larvae in the field in order to ascertain the time when they leave the plant where the eggs were laid, and (iv) the olfactory responses of solitary-feeding fourth-instar larvae to headspace volatiles of the host-plant. Larvae left their initial host-plant during the third or fourth instar. Host-plant headspace volatiles attracted fourth-instar larvae as well as adults; adult females were more responsive than males. Taken together, these results reveal changes in the responsiveness to host-plant volatiles during development, and provide an insight into the host-plant specialization of this butterfly.
Highlights
Host selection behaviour in insects consists of two consecutive phases: (1) search and recognition, usually ending with the finding of one or more potential hostplants, and (2) contact and evaluation, which ends with the acceptance or rejection of an individual plant within a local population of putative host-plants (Schoonhoven et al, 2005)
In this paper we explore the attraction of adults of B. polydamas archidamas to volatiles emitted by Aristolochia chilensis Bridges ex Lindl., describe the aggregation patterns of larvae in the field and determine the response of solitary feeding larvae to volatiles from A. chilensis
Behavioural and EAG bioassays showed that adults of B. polydamas archidamas respond from a distance to volatile chemicals emitted by their host-plant, A. chilensis
Summary
Host selection behaviour in insects consists of two consecutive phases: (1) search and recognition, usually ending with the finding of one or more potential hostplants, and (2) contact and evaluation, which ends with the acceptance or rejection of an individual plant within a local population of putative host-plants (Schoonhoven et al, 2005). Unique insect-plant associations can be established in which an insect species uses a single or a few hostplant species usually containing toxic qualitative defences (sensu Feeny, 1976; Bustamante et al, 2006) which are used by the insect for host recognition. During the searching and recognition phase of host selection butterflies use visual and olfactory sensors located in their eyes and on their antennae, respectively (Hansson, 2002; Nishida, 2005). Among the plant chemicals involved in the establishment of unique butterfly-plant associations are pyrrolizidine alkaloids in the Asteraceae, Fabaceae and Boraginaceae, which are important cues for many species of Arctiids, cyanoglycosides in Passifloraceae for heliconid and acraenid butterflies, iridoid glycosides in various plant families (i.e. Scrophulariaceae, Plantaginaceae, and Verbenaceae) for the common buckeye butterfly (Junonia coenia: Nymphalidae) (Nishida, 2002)
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