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The petroleum fly, ''Helaeomyia petrolei'', is a species of fly from
The larvae ingest large quantities of oil and
California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
, USA
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
. The larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
e feed on dead insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
s and other arthropods that become trapped in naturally occurring petroleum pools, making this the only known insect species that develops in crude oil, a substance which is normally highly toxic to insects.
Description
Adults are about 5 mm long, with black bodies, except for lighter cheeks. Thehaltere
''Halteres'' (; singular ''halter'' or ''haltere'') (from grc, ἁλτῆρες, weights held in the hands to give an impetus in leaping) are a pair of small club-shaped organs on the body of two orders of flying insects that provide info ...
s are yellowish, with white knobs. The densely hairy eyes are nearest at the middle of the face. The third joint of the antennae is slightly longer than the second, the spine of the latter not reaching beyond the apex of the antennae. The hyaline wings are tinged with gray on nearly the entire costal half, except sometimes having a spot toward the apex of the submarginal cell. The apex of the second vein is nearly twice as far from the first as from the apex of the third vein.
Biology
While the larvae normally swim slowly near the surface of the oil with the tips of their air-tubes showing as minute points above the surface film,Esterly 1913 they are able to submerge for longer periods. The mating behavior and egg deposition are still not described, but it is thought that the eggs are not laid inside the oil. The larvae leave it only topupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
te, travelling to nearby grass stems on the margins of the pool. Their whole development between newly hatched larva and pupa takes place exclusively in petroleum.
Petroleum tolerance
The larvae ingest large quantities of oil and asphalt
Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
, and their guts can be seen to be filled with petroleum. However, nutritional experiments showed that they subsist on animal matter present in the oil, which they quickly devour. Although the oil can reach temperatures of up to , the larvae suffer no ill effects from it, even when additionally exposed to 50% turpentine
Turpentine (which is also called spirit of turpentine, oil of turpentine, terebenthene, terebinthine and (colloquially) turps) is a fluid obtained by the distillation of resin harvested from living trees, mainly pines. Mainly used as a spec ...
or 50% xylene
In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are s ...
in laboratory experiments. Oil fly larvae contain about 200,000 heterotrophic
A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
, which have been of interest to scientists searching for microorganisms or enzymes that function in an organic solvent environment. The nitrogen-rich nutrients released into the gut make the environment, with a pH of around 6.5, suitable for the development of these bacteria. There is no evidence that these bacteria contribute to insect physiology.
William Homan Thorpe
William Homan Thorpe FRS (1 April 1902 – 7 April 1986) was Professor of Animal Ethology at the University of Cambridge, and a significant British zoologist, ethologist and ornithologist.Alan Costall, ‘Thorpe, William Homan (1902–1986)’ T ...
referred to ''H. petrolei'' as "undoubtedly one of the chief biological curiosities of the world."
Distribution
The petroleum fly was first described in crude petroleum of the La Brea Tar Pits nearLos Angeles
Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
, California, although the maggots were known to petroleum technologists many years earlier. The population is not considered endangered. The species has since been found in other locations, where the populations are considered sporadic.
See also
* '' Eufriesia purpurata'', a bee that collectsDDT
Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...
References
{{Taxonbar, from=Q4040517 Ephydridae Diptera of North America Endemic fauna of California Insects described in 1899 Taxa named by Daniel William Coquillett Environmental impact of the petroleum industry Fauna without expected TNC conservation status