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Chionea

Chionea is a genus of wingless limoniid crane flies. It consists of two subgenera, the holarctic Chionea and palaearctic Sphaeconophilus. About 37 species are currently recognized in the northern hemisphere,[1] but there are probably several undescribed species. They are commonly called snow flies.

Chionea
Chionea lutescens
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Limoniidae
Subfamily: Chioneinae
Tribe: Cladurini
Genus: Chionea
Dalman, 1816
Type species
Chionea araneoides
Dalman, 1816
Species

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Diversity
ca. 40 species

Description

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Snow fly running in the Cascade mountains

Adults are found during the winter season in forested environments, where they can be observed walking across the surface of the snow. Many species live at high elevations, with some examples of C. nigra found in the Rocky Mountains above 3400 m.[2]

Adults seem to actively seek out the coldest place they can find and drink water by pressing their proboscis against the snow (Marchand, 1917). Adults are not known to feed. Adults have a significantly longer lifespan than other crane flies, living as long as two months.[2]

Chionea are highly active in cold environments that are lethal to most insect species. Adults are often found in motion as they move across the surface of the snow, walking at speeds near their peak velocity.[3] They have been observed walking at speeds at up to 0.8 metres (2.6 ft) per minute in sub-zero conditions,[4][5] and males have been observed to leap when alarmed.[2]

The winglessness of the genus is probably attributable to the fact that at sub-freezing temperatures, it is challenging to generate energy required for maintaining flight. Chionea lack flight musculature, allowing for the storage of additional eggs within the thoracic cavity. However, the halteres have not been reduced and remain innervated. Thus, halteres likely serve as sensory organs for Chionea.[2]

Up to 200 eggs have been found in female snow flies, which are laid singly.[2] The larvae develop in wooded regions, small caves, and rodent burrows. The diet of larvae likely consists of decomposing organic debris, such as decaying leaves, grass stems, and rodent feces found in burrows.[2]

Cold tolerance

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As Chionea are adapted to living on snow and in subnivean habitats,[2][3] they are considered cold tolerant insects. In the wild Chionea are frequently observed at temperatures as cold as 0 and -6°C.[3] In experiments conducted in laboratory environments, Chionea are active and alive until the temperature drops to a mean low of -7°C, their supercooling point.[6][7] Some individuals, however, have been observed to be active at temperatures as low as -17°C.[8][7]

The antifreeze agent found in Chionea hemolymph has been determined to be sugar trehalose.[8] They may also produce glycerol in their hemolymph, preventing them from freezing.[9] Additionally, if a snow fly senses frostbite in its leg, it will instantly self-amputate or detach its leg to prolong survival, much like a lizard detaches a tail if it is attacked.[7]

Reproduction

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Mating is indiscriminate (probably because it is very hard to find a specimen of the other sex for them) and takes 30 to 70 minutes. Winged crane flies and wingless snow crane flies mate tail to tail and this has been verified with video evidence by Vanessa Logsdon et al.

Predators

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One of the reasons why adults emerge in winter seems to be the absence of predators. However, "ice crawlers" (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.[10]

 
A high magnification dorsal view of a snow fly specimen with a nematode dauer placed around the snow fly's cervix ("neck").

Parasites

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Tapeworm cysticercoids, possibly of the genus Hymenolepis, have been found in the abdomens of Chionea stoneana.[2]

While most likely not a parasite of snow flies, a species of nematode, similar to Rhabditis, can sometimes be found in a ringed capsule, which is called a dauer, around the neck of adult snow flies.[2] Immature nematodes develop inside the dauer before ultimately dispersing from it.[2][10] 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. These nematodes are presumed to be phoretic, meaning that they use the snow fly as a mechanism for dispersal, and not snow fly parasites.[2]

Species

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This list was adapted from the "Catalogue of the Craneflies of the World (Diptera, Tipuloidea: Pediciidae, Limoniidae, Cylindrotomidae, Tipulidae)". Naturalis Biodiversity Center. (January 2007).

Subgenus Chionea (Holarctic)

Subgenus Sphaeconophilus (Palaearctic)

See also

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References

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  1. ^ De Jong, Herman; Ciliberti, Pasquale (2014). "How cold-adapted flightless flies dispersed over the northern hemisphere: phylogeny and biogeography of the snow fly genus Chionea Dalman (Diptera: Limoniidae)". Syst. Entomol. 39 (1): 563–589. Bibcode:2014SysEn..39..563D. doi:10.1111/syen.12075. S2CID 86307492.
  2. ^ a b c d e f g h i j k Byers, G. (1983). "Crane fly genus Chionea in North America". The University of Kansas Science Bulletin. 52 (6): 59–195.
  3. ^ a b c Hågvar, Sigmund (1971). "Field observations on the ecology of a snow insect, Chionea araneoides Dalm.(Dipt., Tipulidae)" (PDF). Norsk Entomologisk Tidsskrift [Norwegian Journal of Entomology]. 18 (1): 33–37.
  4. ^ Hågvar, Sigmund (20 Jul 2010). "A review of Fennoscandian arthropods living on and in snow" (PDF). Eur. J. Entomol. 107 (3). 287. doi:10.14411/EJE.2010.037. eISSN 1802-8829. ISSN 1210-5759. S2CID 17539655. Archived (PDF) from the original on 18 Jun 2022. Retrieved 23 Mar 2023.
  5. ^ Hagvar, S.; Vanin, Stefano; Ostbye, E. (Jun 2010). "Contribution to the Fennoscandian distribution of Chionea Dalman, 1816 (Diptera, Limoniidae), with notes on the ecology". Norwegian Journal of Entomology. 57 (2): 166–176. ISSN 1501-8415. Walking speeds from 26-80 cm per minute wererecorded (Fig. 6), with approximately half a meter as a mean value.
  6. ^ Somme, Lauritz; Ostbye, Eivind (1969). "Cold-Hardiness in Some Winter Active Insects" (PDF). Norsk Ent. Tidsskr. 16: 45–48.
  7. ^ a b c Golding, Dominic; Rupp, Katie L.; Sustar, Anne; Pratt, Brandon; Tuthill, John C. (November 2023). "Snow flies self-amputate freezing limbs to sustain behavior at sub-zero temperatures". Current Biology. 33 (21): 4549–4556.e3. Bibcode:2023CBio...33E4549G. doi:10.1016/j.cub.2023.09.002. PMC 10842534. PMID 37757830.
  8. ^ a b Vanin, S; Bubacco, L; Beltramini, M (2008). "Seasonal variation of trehalose and glycerol concentrations in winter snow-active insects". Cryoletters. 29 (6): 485–491. PMID 19280052.
  9. ^ Perry, Lorne (2006). Drawing from the Mountain: An Illustrated Journey. Rocky Mountain Books Ltd. ISBN 978-1-894765-81-7.
  10. ^ a b Schrock, J. R. (1992). "Snow flies". Emporia State University.


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