Helaeomyia petrolei
Encyclopedia
The petroleum fly, Helaeomyia petrolei, is a species of fly
from California
, USA
. The larva
e feed on dead insect
s 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.
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.
The larvae ingest large quantities of oil and asphalt
, 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 38°C, the larvae suffer no ill effects from it, even when additionally exposed to 50% turpentine
or 50% xylene
in laboratory experiments. Oil fly larvae contain about 200,000 heterotrophic bacteria
, which have been of interest for 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
referred to H. petrolei as "undoubtedly one of the chief biological curiosities of the world."
near Los Angeles
, 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.
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
from California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, USA
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The larva
Larva
A larva 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
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s that become trapped in naturally occurring petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
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. The halteres 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, 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 to pupaPupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
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
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
, 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 38°C, the larvae suffer no ill effects from it, even when additionally exposed to 50% turpentine
Turpentine
Turpentine is a fluid obtained by the distillation of resin obtained from trees, mainly pine trees. It is composed of terpenes, mainly the monoterpenes alpha-pinene and beta-pinene...
or 50% xylene
Xylene
Xylene encompasses three isomers of dimethylbenzene. The isomers are distinguished by the designations ortho- , meta- , and para- , which specify to which carbon atoms the two methyl groups are attached...
in laboratory experiments. Oil fly larvae contain about 200,000 heterotrophic bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, which have been of interest for 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
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
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
William Homan Thorpe FRS was Professor of Animal Ethology at the University of Cambridge, and a significant British zoologist, ethologist and ornithologist....
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 PitsLa Brea Tar Pits
The La Brea Tar Pits are a cluster of tar pits around which Hancock Park was formed, in the urban heart of Los Angeles. Asphaltum or tar has seeped up from the ground in this area for tens of thousands of years. The tar is often covered with water...
near Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
, 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.