Ceratosolen corneri behaviour

Rodriguez, Lillian J., Young, Freya, Rasplus, Jean-Yves, Kjellberg, Finn & Compton, Stephen G., 2017, Constraints on convergence: hydrophobic hind legs allow some male pollinator fig wasps early access to submerged females, Journal of Natural History 51 (13 - 14), pp. 761-782 : 773-775

Ceratosolen corneri behaviour

Males that were crawling around in the central cavity of figs used the front four legs to hold onto the surface of galls if most or all of the liquid had been withdrawn (liquid ratings 0–2). The hind legs remained immobile and were extended behind the insect during these movements. When the males descended between the galls, the hind tarsal claws were then used to hold on to the surface of more centrally located galls, providing stability while the males chewed into galls and then mated with the females inside by inserting their metasoma. If some liquid was present (liquid ratings 1–2), this involved the head and thorax becoming partially submerged in the fig liquid, while the hind legs and propodeal spiracles remained clear of the liquid. When the males wished to move elsewhere, bending of their hind legs drew them back from the liquid and they could then proceed to walk over the surface of the galls again.

Small numbers of emerged males were present in figs that had 50% or more of their central cavity filled with liquid. They either became fully submerged or floated on the surface of the liquid. Those that were submerged were usually found dead, or quickly died. Those that floated on the surface held their hind legs in a characteristic way ( Figure 10 ) with the flattened and seta-lined areas of the femora resting on the surface of the liquid. The hind legs in combination formed a trapezium shape when viewed from behind. Their liquid-repellent properties resulted in the surface of the liquid extending downwards between the legs onto the base of the abdomen and the propodeal spiracles located there. This had the appearance of an air bubble trapped between the legs, but it remained continuous with the surface of the liquid. Males in this position were usually immobile, but could remain alive for at least 30 minutes, and when removed from the fig liquid they became active and behaved normally when placed on the surface of galled ovules. In contrast, males that were fully submerged and completely wet did not return to the head-down floating position, and became comatose. Three submerged wasps that remained below the surface of the liquid were observed with isolated air bubbles between the hind legs and abdomen. Although alive, they were incapacitated by the buoyancy of the air bubble and could not control their movements inside the liquid.

Figures

Figure 10. Resting position of the hind legs of a male Ceratosolen corneri when floating in a headdown position on the surface of distilled water. The water-repellent legs ensure that the propodeal spriracles (anterior to the base of the gaster) remain clear of the water surface.