New findings on life history traits ofXenos peckii(Strepsiptera: Xenidae)

Abstract

We studied life history traits of Xenos peckii Kirby (Strepsiptera: Xenidae), a littleknown parasite of the paper wasp Polistes fuscatus (Fabricus) (Hymenoptera: Vespidae) in North America. We field-collected 24 wasp nests in early July 2012, isolated parasitised wasps, tracked life history events of X. peckii, and recorded such behaviour as emergence of males and mating by normal-speed and high-speed cinematography. To emerge, males first cut the puparium with their mandibles along an ecdysial suture line, and then push aside the pupal cap during emergence. The endoparasitic females engage in active calling (pheromone release) behaviour by slowly inflating their cephalothorax, and then extruding it even farther out of, and tilting it away from, the host wasp abdomen. Seasonal and diel (afternoon) emergence periods of males coincide with seasonal and diel receptivity and calling periods of females. Males approach calling females in a swaying flight with smooth turns. They typically land on the anterior portion of the host wasp's abdomen, and then step backward until they make contact with the cephalothorax of the female. As soon as their mesothoracic legs contact the female's cephalothorax, they curl around it, and the male initiates mating. Thereafter, the female fully retreats and never re-mates. et le faisant pivoter loin de l'abdomen de la guêpe hôte. Les périodes d'émergence saisonnières et journalières (en après-midi) des mâles coïncident avec les périodes saisonnières et journalières de réceptivité et d'appel des femelles. Les mâles s'approchent des femelles en appel en un vol sinueux à virages en douceur. Ils se posent typiquement sur la partie antérieure de l'abdomen de la guêpe hôte et reculent jusqu'à ce qu'ils entrent en contact avec le céphalothorax de la femelle. Dès que les pattes mésothoraciques du mâle touchent le céphalothorax de la femelle, elles se replient autour de lui et le mâle commence l'accouplement. Ensuite, la femelle se retire totalement et ne s'accouple plus.

We do not select, nor are we choosy: reproductive biology of Strepsiptera (Insecta)

“…After a male X. peckii has been attracted to a female, he typically lands on the anterior dorsal section of the host wasp's abdomen and then steps backwards until he makes contact with the female's cephalothorax (see Supporting information, Video Clip S2). A sensory patch on his metathoracic legs, as described on legs of other strepsipterans (Dubitzky, ; Pohl & Beutel, ; Henderickx, ), appears to mediate sensory recognition of the female: as soon as the mesothoracic legs touch the female's cephalothorax, they grasp it tightly, and the male initiates copulation through the opening of the female's brood canal (Hrabar et al ., ) (see Supporting information, Video Clip S2).…”

“…Whether these observations on X. peckii and H. silwoodensis apply to other strepsipteran taxa will become apparent as more studies are conducted. Interestingly, there is a distinct diel periodicity of the females ‘calling’ behaviour, which coincides closely with the diel periodicity of the males’ emergence from their puparia (Hrabar et al ., ). This remarkable synchronization of the females’ and the males’ reproductive cycles may help ensure that the short‐lived males (3–6 h) have the best possible chance of locating the cryptic, endoparasitic females (Fig.…”

“…Males of Halictophagus silwoodensis Waloff (Halictophagidae) search first with their front tarsi for the endoparasitic female in the host Ulopa reticulata (F.), and then bend their abdomen for copulation (Henderickx, ). Males of Xenos peckii Kirby approach host wasps in response to the ‘calling female’, which assumes a particular calling posture (see below; Hrabar et al ., ) (Fig. ) (see Supporting information, Video Clip S1).…”

“…This ‘calling’ posture, as Hrabar et al . () suggest, might help disseminate pheromones and provide visual cues for mate‐seeking males. It may also facilitate contact chemo‐recognition through aligment with sensory patches on the males’ tarsi.…”

The unusual eyes ofXenos peckii(Strepsiptera: Xenidae) have green- and UV­-sensitive photoreceptors

“…In X. peckii, the larviform female is situated primarily within the abdomen of her wasp host. Although it recently has become clear that she actively participates in attracting a male (Hrabar et al, 2014), only a small and, for our eyes, rather cryptic portion of her body is exposed. Still, the male finds her often enough to propagate the species, and his unique strepsipteran eye type (Buschbeck et al, 1999(Buschbeck et al, , 2003 may play an important role in that.…”