50 Million-Year-Old Assassin Bug Has Its Unusually Well Preserved Bits On Show


Rachael Funnell

Social Editor and Staff Writer

clockJan 19 2021, 15:25 UTC
rare fossil perfectly preserved the genitals of an assassin bug

That feeling when you get fossilized for 50 million years with your junk out. Image courtesy of Daniel Swanson and the Palaeontological Association

It might sound like a chapter in So You’ve Been Publicly Shamed, but to find a preserved insect specimen with visible genitals is actually a cause for celebration among scientists. A new study published in the journal Papers in Palaeontology describes one such specimen, an assassin bug from 50 million years ago which has been suspended in amber, with even delicate structures still intact.

It’s a lucrative find for many reasons, academically speaking, but the unique preservation of its genital capsule (known to entomologists as a pygophore) is particularly remarkable. Upon inspection, the researchers on the new paper realized that the internal features of the ancient bug’s genitalia were clearly visible and well-preserved, providing new insights into the love lives of ancient bugs. Such intricate detail is, while not unheard of, very rare in fossilized insect specimens.


“One reason [for this] is that genitalic structures are in part composed of membranous structures, which do not preserve well,” wrote researcher on the study Daniel Swanson, a graduate student in entomology at the University of Illinois Urbana-Champaign, in an email to IFLScience. “Even in our fossil, the preserved genitalia is largely represented by the sclerotized, or hardened, portions of the genitalia. Another fortuitous characteristic of this fossil is that the two parts came from a coronal split, which affords us an internal view of these structures. Compression fossils usually just preserve either a view of the back or the belly, in which cases you can't really see any of the internal anatomy.”

The specimen also represents a new genus and species for assassin bugs. Surviving species still roam the Earth today, some of which carry around a backpack made of dead ants. The unusual accessory is thought to provide camouflage for the striking insects, who suck out the innards of their prey before gluing them to their back with viscous saliva.

assassin bug dead ants backpack
"The dead ants really bring out my eyes," - Extant assassin bugs. Kurt_G/

This new species, named Aphelicophontes danjuddi, was recovered from the Green River Formation in present-day Colorado. It can be seen sporting a bold banding pattern on its legs, and appears to be frozen in time playing table tennis – but the “paddle” is actually a smaller beetle, also stuck in the amber.


“While not impossible, there is no evidence to suggest the beetle was prey for the assassin bug,” wrote Swanson. “What seems more likely is that the beetle simply suffered the same fate as the assassin bug, either drowning or dying and subsequently falling in the water and then sinking and preserving alongside the assassin bug. Sometimes water flow and pooling can lead to aggregations of lots of dead insects which sink and preserve in a clump. We call these types of fossil aggregations "rafts".”

The fossil is a fortuitous one with an interesting story, having first been discovered as the result of cracking open a rock that split the insect near-perfectly down the middle. The two halves were sold by a fossil dealer to two different collectors, meaning the researchers went on something of a treasure hunt to track down both halves and reunite them for this study.