Parasitism of Leucauge tessellata (Araneae: Tetragnathidae) by a koinobiont polysphinctine wasp of the Acrodactyla genus-subgroup (Hymenoptera: Ichneumonidae)

Abstract

Polysphinctine wasps have evolved highly specialized life strategies that allow them to parasitize different spider hosts effectively. In this report, we document juvenile orchard orb-weavers Leucauge tessellata (Thorell, 1887) singly carrying larvae of a polysphinctine wasp from the Acrodactyla quadrisculpta-group. The wasp was identified using its morphological characteristics, mode of parasitism, and mt-COI phylogenetic analysis. Observations revealed that all three Acrodactyla sp. larvae collected were attached to the left mediolateral abdomen of the host spiders, where they consumed hemolymph until pupation. Before being killed by their parasitoids, host spiders exhibited modified web-building behavior, constructing a reduced cocoon web in place of the characteristic orb web of L. tessellata. Our PLS-PM analysis showed a significant negative correlation between the host spider's developmental stage and the parasitism rate (P = 0.02), which suggests that Acrodactyla sp. wasps selectively target juvenile L. tessellata, likely because they are less able to dislodge the larva from its attachment site compared to adult spiders. We speculate that the apparently consistent site of larval attachment in this specific spider-parasitoid interaction may represent a specific host-utilization adaptation in the observed Acrodactyla sp. wasps. Further investigation is warranted to strengthen evidence for our interpretation of this behavior and to explore its evolutionary implications.

Brian T. Sabanal, Yong-Chao Su "Parasitism of Leucauge tessellata (Araneae: Tetragnathidae) by a koinobiont polysphinctine wasp of the Acrodactyla genus-subgroup (Hymenoptera: Ichneumonidae)," The Journal of Arachnology, 53(3), 165-170, (2 January 2026) https://doi.org/10.1636/JoA-S-24-028

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