Innovation on the fly: 100m-year-old parasite found in Myanmar injected larvae into hosts so they could eat them from the inside out

Chinese team claim ‘bizarre’ zhenai xiai is world’s oldest recorded fly to feast on its hosts, suggesting these were among the first parasitoid insects in the history of evolution

PUBLISHED : Friday, 08 January, 2016, 12:15pm
UPDATED : Monday, 12 June, 2017, 12:53pm

A winged insect that was trapped in amber nearly 100 million years ago is believed to be the earliest known parasitic fly to grow up inside a foreign host and then eat it from the inside out, according to a new study by Chinese scientists.

The researchers described the creature “bizarre” because it had features never before seen in flies from this period in history.

This suggests the fly - which belongs to the insect order Diptera - had likely developed a sophisticated system to exist as a parasitoid at a time when dinosaurs still roamed the earth.

A parasitoid spends a large chunk of its life attached to, or within, a single host organism in a relationship that is basically parasitic. The chief difference is that later sterilises or kills, and occasionally eats, the host.

The one-centimetre-long specimen has been named zhenia xiai after the Chinese words for needle (zhen) and summer (xia), but with Latin suffixes added.

It was found in a piece of amber from Myanmar and dates back 99 million years, according to a recent paper published in the The Science of Nature journal by a team led by Dr Wang Bo at the Nanjing Institute of Geology and Palaeontology in China’s eastern Jiangsu province.

What struck the palaeontologists first was its exceptionally large eyes, which covered most of the fly’s head.

The extreme size of its compound eyes created space for thousands of individual photonic sensors to provide a wide viewing range and also allow it to quickly detect even the faintest of movements, the team said.

The eyes also indicated an extremely well-developed visual system that would probably have helped the fly discover and lock on to a host amid thick forest vegetation in dimly lit conditions, according to Wang and colleagues.

After spotting a host, the fly would use the claws on its three enlarged toes to firmly grip its subject, which is believed to have been a soft-bodied creature such as a worm or the larva of other insects.

It would then use it “highly developed”, needle-like ovipositor to inject its eggs into the host.

An ovipositor is a long protruding organ used by some animals to lay eggs. It can be made up of one, two or three pairs of appendages. In the case of the zhenai xia, these were covered by hard protective plates.

“Our results suggest that eremochaetids (flies) are among the earliest recorded parasitoid insects,” the researchers reported in their paper.

“Parasitoidism is a key innovation in insect evolution,” they said.

“Our findings reveal an unexpected morphological specialisation of flies and broaden our understanding of the evolution and diversity of ancient parasitoid insects.”