Pachysomoides
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Pachysomoides stupidus
Pachysomoides stupidus is a gregarious ichneumon wasp that parasitizes paper wasps (Polistes spp.). Females lay multiple eggs on pre-pupal Polistes grubs, and larvae feed gregariously as external parasites on the pupa. The species exhibits larval competition among siblings for host resources, with males showing more altruistic behavior than females in resource allocation. Brood sex ratios are biased toward females, with investment ratios equalized by egg-layers.