Sniffing Out a Meal

Figwort Weevil, Cionus scrophulariae

The wonderfully patterned Figwort Weevil (Cionus scrophulariae) is a fairly common but shy animal in Ireland that can be found on plants of the family Scrophulariaceae. The larvae may also be seen here, covered with a shiny, sticky substance. This is a diffuse peritrophic membrane that acts as a deterent to any potential predators (1). Production of this membrane in the posterior mid-gut stops once the larva has stopped feeding and a new, ribbon-type structures begin to be made which are used to construct cocoons.

Figwort, Scrophularia nodosa

The weevil's main food source is the Figwort (Scrophularia nodosa) from where it gets its name. Figwort is an excellent coloniser, but mainly of waste ground and populations are therefore often scattered across an area. C. scrophulariae can find these populations using odors from Figwort. The larger the patch size of Figwort plants, the stronger the odor and the higher the density of  C. scrophulariae individuals associated with them (2).

References:

1. Tristram, 1978. Journal of Insect Physiology 24 pp. 391-398
2. Anderson and Hambäck, 2011. Athropod-Plant Interactions 5 pp. 269-277