| 词条 | Chionea |
| 释义 |
| image = Chionea sp. - MUSE.jpg | image_caption = Chionea sp. Reconstrution - scale 20:1. (MUSE - Science Museum, Trento) | image_width = 250px | regnum = Animalia | phylum = Arthropoda | classis = Insecta | ordo = Diptera | subordo = Nematocera | infraordo = Tipulomorpha | superfamilia = Tipuloidea | familia = Limoniidae | subfamilia = Chioneinae | tribus = Cladurini | genus = Chionea | genus_authority = Dalman, 1816 | diversity_link = | diversity = ca. 40 species | type_species = Chionea araneoides | type_species_authority = Dalman, 1816 | subdivision_ranks = Species | subdivision = see text. }} Chionea is a genus of wingless limoniid crane flies. It consists of two subgenera, the holarctic Chionea and palaearctic Sphaeconophilus. About 40 species are currently recognized in the northern hemisphere, but there are probably several undescribed species. They are commonly called snow flies. DescriptionAdults occur during winter, where they can be observed walking over snow. They produce glycerol in their hemolymph, preventing them from freezing. Up to 200 eggs have been found in female snow flies, which are laid singly (Schrock, 1992). The larvae occur under decaying leaves in wooded regions (Marchand, 1917). At least the larvae of some species seem to feed on feces in rodent burrows (Schrock, 1992). Adults seem to actively seek out the coldest place they can find and drink water by pressing their proboscis against the snow (Marchand, 1917), but are not known to feed. Adult snow flies live for up to two months. They can walk at a speed of about 1,30 m per minute, and at least males have been observed to leap, without being provoked (Schrock, 1992). Male C. alexandriana are about seven millimeters long. They are easiest found on snowbanks in the afternoon, in areas that are to some extent forested. Some species have been found to be abundant on the floor of caves (Schrock, 1992). The winglessness of the genus is probably attributable to the fact that at sub-freezing temperatures, it is very hard to generate enough energy for maintaining flight muscles. Also, the space normally taken by flight muscles is used to store eggs. However, the halteres have not been reduced and are innervated, thus probably serving as sensory organs (Schrock, 1992). ReproductionMating is indiscriminate (probably because it is very hard to find a specimen of the other sex for them) and takes 30 to 70 minutes. While winged crane flies face in opposite directions, snow flies position themselves similar to many beetles.[https://web.archive.org/web/20060914150800/http://www.emporia.edu/ksn/v38n2-may1992/slideshow/pages/i_gif.htm] This requires the male copulatory organs to be inverted 180 degrees (Schrock, 1992). PredatorsOne of the reasons why adults emerge in winter seems to be the absence of predators. However, "rock crickets" (Grylloblattidae) have been shown to feed on them. Because the cysticercoid form of a tapeworm species has been found in two out of three C. stoneana specimens in eastern Kansas, they also have to be eaten by mice, which are the tapeworm's host. The snow fly larvae likely take up these tapeworms via mouse feces (Schrock, 1992). ParasitesA species of nematode, similar to Rhabditis, is sometimes found in a ring around the neck of adults. It has been speculated that the female nematode lays this ring around the fly's neck when it emerges from the pupa and cannot yet move properly. Nematode offspring will develop inside this ring and is dispersed in this way. (Schrock, 1992). SpeciesThis list was adapted from the [https://web.archive.org/web/20100425044209/http://ip30.eti.uva.nl/ccw/index.php Catalogue of the Craneflies of the World] (January 2007). Subgenus Chionea (Holarctic)
Subgenus Sphaeconophilus (Palaearctic)
References
Further reading
External links
See also
3 : Limoniidae|Nematocera genera|Taxa named by Johan Wilhelm Dalman |
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