Fleas are highly specialized insects in the class Insecta. The adults are wingless, small and flat. Flea is an exoparasitic insect in the order fleas. It sucks the blood of mammals (including humans) and birds. Its body length is usually only 1 ~ 3 mm.
In the era of giant dinosaurs, did fleas once grow very big?
Chinese paleontologists have discovered some giant flea fossils of the Middle Jurassic in Ningcheng, Inner Mongolia (about 165 million years ago) and the early Cretaceous in Beipiao, Liaoning (about 125 million years ago). They are about 1.5 cm long and some species can even exceed 2 cm. They are the earliest fleas found so far. These Mesozoic fleas are as wingless as living fleas, and females are usually larger than males. However, their body shape is not flat on the side, but closer to the flat back and abdomen; The antennae are short, but they have more nodes (16 ~ 19 nodes, and the current species is 11 nodes); It has a long thorn suction mouthpiece; The feet are very long, with various Chlamys bristles, but the hind feet are not jumping like the living species, and the claws are very long; There is a large backward mane on the chest and abdomen.
Giant fleas have Chlamys like bristles on their feet and dense backward manes on their body surface, indicating that they are suitable to parasitize on the body surface of hairy vertebrates. Mammals and hairy dinosaurs of the same age as these giant fleas may be hosts. If the host is a mammal, giant fleas may mainly hide in the nest of the host and suck blood in time, because the size of mammals at that time was very small, so it was difficult for such a large flea to hide on its body surface. If the host is a hairy dinosaur, fleas may parasitize on its body surface. The long, sharp and file toothed mouthparts of giant fleas can penetrate the tough skin of these dinosaurs.