Invasive Parasitic Wasps Spread Across the US, Threatening Native Ecosystems

As of September 5th, 2025, scientists have discovered two previously unknown species of parasitic wasps that have been spreading across the United States, from New York to the Pacific coast. Originally from Europe, these tiny predators lay their eggs inside oak galls, where their larvae gradually consume the bodies of native oak gall wasps before emerging as adults.

The adult female wasp injects one or more eggs into or onto the body of a host insect, in this case, oak gall wasp larvae inside galls. When the eggs hatch, the larvae begin to consume the host's non-essential tissues first, keeping the host alive as long as possible to provide a fresh food source. Over days to weeks, the larva progressively eats the host's tissues, eventually consuming it entirely.

Experts suggest the parasitic wasps may have come to the US through imported oak trees or by hitchhiking on planes before exploding in population. While there is no direct threat to humans, scientists have warned that the wasps could upheave America's ecosystem. They may not only target oak gall wasps but also potentially compete with or displace native parasitic wasps, which play a critical role in controlling insect populations, maintaining ecosystem balance, and supporting biodiversity.