A wide range of modern Insects survive as ectoparasites of vertebrates, either by living permanently on their hosts, as with Fleas or by visiting animals to feed, as with Mosquitoes. However identifying such behaviour in the fossil record is difficult, and while a variety of parasitic insects are known from Cainozoic deposits, only Fleas are known from the Mesozoic, when most modern Insect groups are thought to have originated.
In a paper published in the journal eLIFE on 24 June 2014, a team of scientists led by Jun Chen of the Institute of Geology and Paleontology at LinyiUniversity describe a remarkable Fly larvae (maggot) from the Middle Jurasic Daohugou beds of Ningcheng County in Inner Mongolia.
The larvaeare formally named as Qiyia jurassica, where ‘Qiyia’ means ‘bizarre’ in Chinese and ‘jurassica’ refers to the age of the specimens. The species is described from five specimens preserved as surface impressions on grey siltstone. Two of these specimens have been compressed laterally and three dorsally, enabling the species to be examined from both angles.
Qiyia jurassica from the Middle Jurassic epoch of Daohugou, China. (A) Specimen preserved in lateral view. (B) Specimen preserved in lateral view under alcohol (horizontal mirror image). (C) Head capsule of specimen preserved in lateral view. (D) Head and thorax of specimen preserved in lateral view. (E) Enlargement and reconstruction of the mandible of specimen preserved in lateral view;note the longitudinal groove. (F) Fifth proleg of specimen preserved in lateral view; note stiff, upward directed bristles which are distinctly longer than setae on body. (G) Last abdominal segment of specimen preserved in lateral view. Abbreviations: ap, anal papilla; p, proleg; pr, process of ridge; tp, terminal process. (Scale bars: 5 mm in A, B, 1 mm in D, F, G, and 0.5 mm in C, E). Chen et al. (2014).
The specimens range from 18.1 mm to 23.8 mm in length. It has elongate, sickle-shaped mandibles, which are interpreted as an adaption to blood-sucking, and what appears to be a round sucker on the dorsal surface of its thorax, presumably with which to adhere itself to its prey.
Qiyia jurassica from the Middle Jurassic epoch of Daohugou, China. (A) Specimen preserved in dorsal view under alcohol. (B) Head and thorax of specimen preserved in dorsal view; note the underlying thoracic sucker. (C) Terminal processesof specimen preserved in dorsal view. (D) Reconstruction of sucker. The sucker consists of a circular suction disc with centralopening and thin peripheral area. Six robust, radially arranged ridges are covered by soft skin with small spines. (E) Head and thorax of specimen preserved in dorsal view; note the deformed mandible. ap, anal papilla; p, proleg; pr, processof ridge; tp, terminal process; tr, tentorialrod. (Scale bars: 5 mm in A, 1 mm in B, C, E). Chen et al. (2014).
The larvae are interpreted as having belonged to a Water Snipe Fly (Athericidae). Modern Water Snipe Flies are blood parasites of vertebrates as adults, with larvae that are aquatic predators, living in fast flowing water and targeting smaller invertebrates. The Water Snipe Flies are considered to be the sister group to the Horse Flies (Tabanidae), making it likely that the common ancestor of the two groups was also a blood sucker, although neither group produces blood drinking larvae today, so it is unclear whether the adaptation seen in Qiyiajurassica is a separate innovation (the larvae of all True Flies metamorphose on maturity, and seldom have a larval lifestyle that even remotely resembles that of adults), or whether parasitism was the ancestral state in both larval and adult members of these groups. Fossils of adult Horse and Water Snipe Flies are known from the Early Cretaceous of southern England, with molecular studies suggesting the groups diverged in the Early-to-Middle Jurassic, but this is the first fossil evidence of either group prior to the Cretaceous.
Reconstruction of Qiyia jurassica in lateral view. Chen et al. (2014).
The Daohugou beds are interpreted as a lake environment, with largely still waters. No fish have been recorded from these beds, but Salamanders are extremely numerous here, and were presumably the host group for Qiyia jurassica. Salamanders have thin skin, making them vulnerable to blood-sucking parasites, and those from the Daohugou beds are believed to have been aquatic throughout their entire lifecycle, reaching maximum lengths of about 500 mm. This is about the right size for a parasite the size of Qiyia jurassica, and means that an attached larvae would have been unlikely to have been removed from the water by its host.
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