| Hydrotaea | |
|---|---|
| Female Hydrotaea dentipes | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Diptera |
| Family: | Muscidae |
| Subfamily: | Azeliinae |
| Tribe: | Azeliini |
| Genus: | Hydrotaea Robineau-Desvoidy, 1830 |
| Type species | |
| Musca meteorica Linnaeus, 1758[1] |
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| Synonyms | |
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Hydrotaea are insects located in most regions of the world, but are more populous in warmer climates. They are often found on excrement in summer months, and are therefore generally found in close proximity to livestock. Among the 130 known species in this genus, the most commonly recognized is the dump fly.[2] This common name was given because of its ideal landing spot on fermenting feces. Along with many others in the family Muscidae, Hydrotaea is of great forensic importance in both the economic and public health scene.
“Many authorities consider Diptera to be the most important order to medical/veterinary entomology."[3]
Certain Hydrotaea species have been proven to carry and transmit certain diseases to warm blooded animals, including humans.[4] Researchers continue to monitor these vectors of disease as they have been connected with the spread of mastitis.[5] Hydrotaea is very important to medicine and livestock as well as forensics.
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There are 130 known species in this genus from the family Muscidae. Many of these are of forensic importance. Some of the more common species include:[2]
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Larvae of this genus are often dimorphic obligative carnivores, meaning that the second and third instars are predators. This ranges depending on the species, some are carnivorous in all three instars. However, regardless of the species, all final instar larvae are always carnivorous with some strongly cannibalistic. Their growth varies with the smallest being under 6 mm[6] and the largest being up to 16 mm.[7] Their abdomen has ventral welts and large spiracles with sinuate slits. They prefer to live in areas with high bacterial fermentation, so they are often found in vegetation or feces.[2] Most species prefer to lay eggs in pastures and in long grass.
Adults are mostly sweat flies and dump flies that strongly prefer mammal blood. They are able to reopen wounds that are almost completely healed. Mouthparts range from mainly sponging mouthparts to some with rasping teeth. Many have enlarged prestomal teeth. The metathoracic spiracle is covered in thick, long setae and is rounded triangularly.[7] The average size for the genus is 6.5-8.5 mm for males and 5.75-7.5 mm for females. They range from a very light brown to bluish black with large, red eyes and plumose antennae.
Flies in this genus are found in the warmer parts of North and South America, Europe, Asia, and Australia. They are most commonly found in urban settings. They prefer fermenting areas so they are often found in vegetation, feces, or decomposing carcasses. It is a tertiary strike fly, so it is only seen on bodies that have been dead more than ten days.[2]
Research has been performed on this insect’s lifecycle, namely Hydrotaea rostrata, in an attempt to better understand the time elapsed in crime related situations in Australia. Mature flies will seek out decaying substances, preferably material in which an extended amount of time has elapsed since death. This trait is key in aiding forensic entomologists in the area. Masses of maggots, which are often characteristic of other species of flies, is not typical of H. rostrata. The larvae of this species can be divided in three stages, or instars, which is then followed by the formation of a pupa. After this event, the larvae will become mature flies. The whole process takes between 518.4 and 1555.6 hours according to one study in Australia, performed by IR Dadour, D.F. Cook, and N. Wirth, who reared the insects starting from eggs under varying environmental conditions. The warmer summer-like temperatures, 25 °C (77 °F) and 19–30 °C (66–86 °F), tended to favor a shorter period of time to adulthood, on estimate 21.6 and 23.5 days. In contrast, the cooler winter-like temperatures, 15 °C (59 °F) and 12–18 °C (54–64 °F), favored a longer period of time to adulthood, on estimate 64.5 and 48.3 days.[8]
The larvae of another species of Hydrotaea, H. aenescens has actually been incorporated into agricultural life in certain scenarios. This insect, also known as the black dump fly, has larvae which tend to inhabit fecal material and are capable of consuming other larvae in the vicinity as a source of nourishment. The larvae attacked are notably that of Musca domestica, the housefly.[9] Thus, farming establishments wishing to utilize this larval trait to their advantage are able to purchase the insects for their operation[9]
This fly larva, aside from uses in the agricultural community is considered relevant in the field of forensic entomology as it commonly located right below corpses.[10]
On an interesting side note in the realm of larvae, the larvae of flies such as Hydrotaea irratitans are known to be cannibalistic[5] and are capable of seeking shelter underground to survive cold conditions.[4]
Research has incriminated Hydrotaea irritans as a vector of summer mastitis, a bovine infection that can be caused by multiple suspected bacteria.[5] The aforementioned research allowed flies doctored with select bacteria from a sample representing summer mastitis to come in contact with the udder region of cattle which had been nicked for the study. In order to accomplish this, flies were placed in specialized cage-like devices that were attached to the udder region of the cattle. The selected bacteria appeared in the secretions produced from this experiment in a few of the cows used, as well as on the physical bodies of a little over a third of the doctored flies. Among the bacteria found in the fluid obtained, thus carried by H. irritans were[5]
It should be noted that cows are not the sole victim of H. irritans, as this fly is also known to target many other warm-blooded animals as well, humans included.[4] Aside from H. irritans, another species of Hydrotaea, H. aenescens, is also reported to carry Salmonella serovar infantis, as well.[11]
There are no predators of Hydrotaea sp. that any other fly species would not have in common. However, Hydrotaea aenescens can be very useful to have around a manure habitat, which they naturally inhabit because Hydrotaea aenescens kill house fly larvae.[12]
Hydrotaea species have been helpful in forensic cases worldwide by allowing identification of the post-mortem interval (PMI),[10] in multiple noted cases. This particular species typically arrives to the scene 4–5 months after a carcass has begun great decomposition.[6] This indicates that it arrives on scene after much decay and decomposition has occurred and it succeeds several other species. When Hydrotaea is found during an investigation it is usually a sign that the corpse was not burned and that the Calliphoridae species, or blow fly, phase has been completed.[13] Hydrotaea sp. can be facultative predators in their second and third instars, this means that they can feed on one another or other fly species that precede them, such as the blow fly. This is important to the investigators because they must include additional time to the PMI since the Hydrotaea sp. may have eaten flies or larvae that preceded their arrival. Every hour in the PMI is significant because the difference in one hour of death could change the cause of death.[6]
For this species, there is no future research being done at the moment. As of now however, Hydrotaea sp. can be used to identify drug verification along with determining if a body was relocated. Current research into Hydrotaea spinigera has come to show that it makes up roughly seventy percent of the Muscidae found on a body that is discovered in a forest region.[14] Along with this, Hydrotaea rostrata was found to arrive at a decomposing body on the second day of decay, once the body started to decay, and stayed for a duration of thirty four days, or until the body had reached a skeleton state of decomposition.[15] The research of Hydrotaea irritans and the spread of mastitis as it pertains to live stock is also a point of interest as mentioned above.