The insects that lived 160 million years ago had eggs on their legs. Evidence of brood care, in which a parent protects their eggs or young offspring by carrying them, may be the earliest example of this behavior.
The fossils of insects were excavated from the Haifanggou Formation, which is located in northeastern China. Many fossils have been recovered from the site in the past, including feathered dinosaurs, ancient mammals, giant fleas, and long-proboscid scorpion flies.
The study was published in the journal Proceedings of the Royal Society B: Biological Sciences. The fossils are 163.5 million years old, meaning they were in the middle of the dinosaurs.
There are 30 adult female specimen with a cluster of eggs anchored to their left "mesotibia," the middle leg in their trio of left-side legs. The densely-packed eggs were arranged in five or six staggered rows with six to seven eggs per row. The size of each egg is about 0.04 to 0.05 inches across, which is quite large.
After 70 years, a lost fossil treasure trove has been found.
The study authors theorize that K. popovi females lay the eggs on their legs by first hiding a sticky mucus and then bending their abdomens to expel the eggs onto the limb. They wrote that the mesotibia might have been used to maintain balance.
The authors noted that the large eggs of the water bugs likely had an adequate supply of nutrition for their offspring. Small eggs are easier to aerate with oxygen than large eggs due to their low surface area. The flow of oxygen from the surrounding water to their developing offspring may have been maximized by carrying eggs on their legs.
The study authors said that carrying a cluster of eggs on one leg is not unusual in aquatic arthropods. The evidence of definitive brooding behavior in insects has been pushed back by almost 38 million years, which is helpful for understanding the evolution and adaptive significance of brood care in insects.
It was originally published on Live Science
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