Fossil fungi trapped in amber reveal ancient origin of parasitic zombie-ants

Holotype of P. ironomyiae sp. nov. (NIGP203272) from mid-Cretaceous Kachin amber (~99 million years ago) and the comparison with extant Ophiocordyceps fungi. Credit: Proceedings of the Royal Society B: Biological Sciences (2025). DOI: 10.1098/rspb.2025.0407

Chinese Academy of Sciences researchers report that fossilized entomopathogenic fungi from mid-Cretaceous amber reveal some of the oldest direct evidence of parasitic relationships between fungi and insects, suggesting that Ophiocordyceps fungi originated approximately 133 million years ago and underwent early host shifts that shaped their evolution.

Entomopathogenic fungi have evolved extraordinary ways to turn insects into unwitting accomplices in their own demise. Among the most famous are the “zombie ant fungi,” Ophiocordyceps unilateralis, which infect carpenter ants in tropical rainforests. After infecting the ant’s body, the fungus hijacks the host’s nervous system, compelling it to abandon the safety of its nest.

The ant becomes a macabre six-legged marionette, compelled to climb a plant to a height above the colony, where it clamps its jaws onto a leaf. Locked into a final death grip, the ant dies while the fungus slowly consumes its tissues. After a while, a spore-producing stalk erupts grotesquely from the back of the ant’s head, scattering infectious spores down onto the forest floor to restart the cycle with fresh victims.

But ants are far from the only victims of fungal mind control. In grasslands and fields, entomopathogenic fungi like Entomophthora grylli invade grasshoppers and crickets, orchestrating a similar, chilling scenario known as “summit disease.” As infection progresses, the insect abandons its usual behavior, ascending to the tops of grasses or tall weeds. There, it perches in a characteristic posture, often gripping the plant with its legs stretched outward.

As the fungus bursts through the exoskeleton, it releases clouds of spores that drift down onto the unsuspecting insects below. In some cases, related fungi have been observed driving their hosts to wander aimlessly before ultimately walking into streams or ponds, where they drown, ensuring the fungus can grow in the moist environment that best suits it.

Flies, too, fall prey to fungal manipulation. Entomophthora muscae infects common houseflies, also driving them to climb to high spots, upper corners of windows or walls, just before death. There, the fly extends its proboscis to glue itself in place, creating the perfect platform for the fungus to erupt through the soft parts of the body. From the cadaver, spore-laden filaments radiate outward, releasing infectious particles into the air to settle onto new hosts.

Even spiders can be commandeered. Some Ophiocordyceps species compel infected spiders to attach themselves to leaves or twigs before succumbing, ensuring the fungus can safely grow a fruiting body that rains spores into the surrounding habitat.

These remarkable strategies highlight the astonishing evolutionary tactics of parasitic fungi. By reprogramming their hosts’ instincts for climbing, gripping, and walking, they orchestrate ideal conditions for their own reproduction. What appears to be mindless self-destruction by the insect is, in reality, the well-executed plan of a fungus perfectly adapted to exploit its host’s body and behavior.

Direct fossil evidence of these relationships has remained scarce, largely because soft fungal tissues rarely fossilize and their pathogenic nature can be difficult to discern in ancient specimens. Previous research has documented only a handful of tentative fossil records, and estimates of the evolutionary origins of Ophiocordyceps fungi relied on limited calibration points and indirect evidence.

In the study, “Cretaceous entomopathogenic fungi illuminate the early evolution of insect–fungal associations,” published in Proceedings of the Royal Society B: Biological Sciences, researchers described two newly identified fungal species preserved in approximately 99-million-year-old Kachin amber.

One of the two fossil fungi described in the study, Paleoophiocordyceps gerontoformicae, occurred in association with an infected ant pupa encased in mid-Cretaceous Kachin amber dated to about 99 million years ago. Researchers assigned the ant host to the extinct genus Gerontoformica, belonging to the subfamily Sphecomyrminae.

Infection likely began inside the nest, since ant larvae do not leave the nest. Workers may have transported fungal spores into the nest and removed the pupa to maintain colony hygiene just as modern ant colonies do. The fossil pupa possibly represents an early instance of such behavior, with disposal outside the nest preceding resin entombment.

Holotype of P. gerontoformicae sp. nov. (YKLP-AMB−010) from mid-Cretaceous Kachin amber (approx. 99 million years ago) and the comparison with extant Ophiocordyceps fungi. Credit: Proceedings of the Royal Society B: Biological Sciences (2025). DOI: 10.1098/rspb.2025.0407

Morphological features of P. gerontoformicae matched characteristics seen in extant myrmecophilous Ophiocordyceps species. A combination of laterally attached ascoma and asexual traits similar to the Hirsutella clade suggested a position near the base of both myrmecophilous hirsutelloid and O. sphecocephala lineages.

Results indicated that Ophiocordyceps likely emerged during the Early Cretaceous, about 133.25 million years ago, earlier than previously proposed estimates of ~100 million years. Ancestral state reconstructions suggest that the genus initially parasitized beetles before undergoing host shifts to Lepidoptera and Hymenoptera during the Cretaceous. Researchers inferred that these transitions coincided with the diversification of moths and ants, which offered new ecological opportunities for fungal specialization.

The authors concluded that the fossils not only document some of the oldest evidence of insect-pathogenic fungi but also support the view that Ophiocordyceps diversified in tandem with its insect hosts.

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More information: Yuhui Zhuang et al, Cretaceous entomopathogenic fungi illuminate the early evolution of insect – fungal associations, Proceedings of the Royal Society B: Biological Sciences (2025). DOI: 10.1098/rspb.2025.0407 Journal information: Proceedings of the Royal Society B