The effects of patch richness on con‐specific interference in the parasitoid Ibalia leucospoides (Hymenoptera: Ibaliidae)

  We experimentally studied con‐specific interference in Ibalia leucospoides , a parasitoid of the woodwasp Sirex noctilio , on pine logs containing variable numbers of woodwasp larvae. Competiton occurred when two different‐sized female parasitoids foraged on a host patch, and consequently the small female always abandoned the patch. Regardless of host density, con‐specific presence did not affect the attack rate, the number of hosts attacked, nor patch residence time by the winner, when compared to a control female that foraged alone. In contrast, con‐specific presence reduced patch time and the number of hosts attacked by the loser. Finally patch time (by both) as well as number of hosts attacked (by the winner only) increased with host density per patch. Our results suggest that con‐specific presence has different consequences for different‐sized females during patch exploitation.