Flesh flies breed on living or dead organic material

Flesh flies, as their name implies, breed on living or dead organic material, mainly flesh. Their maggots live in dead animals, dung or decaying vegetable matter and sometimes in open wounds of mammalian species. 

Some species are internal parasites especially of beetles and grasshoppers while others live in bees and wasps’ nests.

About 30 species are found in the Maltese islands. Most are dark with light stripes but in many cases it is difficult to tell species apart unless they are studied microscopically. 

In many species the female is larger than the male. The most common species, known in Maltese as dubbiena tal-laħam, is larger than the common house fly. It can be found on decomposing organic material as well as on flowers.

These insects which are found throughout most of the world are not only a nuisance but can also be important vectors of diseases including leprosy. Sometimes they are also important as pest control agents and can be beneficial in fruit tree orchards and in forestry plantations.

Flesh flies have been extensively studied especially because of their importance in forensic science. Flesh flies do not lay eggs. The eggs hatch inside the female fly which then ‘gives birth’ to the maggots. 

Different species place their young in animals that are at different stages of decomposition ranging from freshly dead to bloated or decaying. This makes it possible for entomologist to accurately give the date or sometimes even the time of death of a corpse.

There is a tendency to classify insects as being either good or bad. Flies are automatically deemed as bad and therefore to be annihilated. But the living world is not that simple. 

Many species of flies can cause problems but at the same time they also help to break down organic matter and help to recycle it. 

Flies reduce the time required for a corpse to decompose and without them we would see more dead animals lying around. 

This article was written in The Times on 28.09.11

Blue bottles

Bluebottle (Calliphora vicina)

The bluebottle is a common fly. It sometimes enters houses but in winter you are more likely to see it in the countryside especially on sunny days as it sunbathes in a sheltered place to warm up its body. 

It is slightly larger than the much common housefly and has a grey head and abdomen and a bright metallic blue abdomen. 

The body and legs are covered in short stiff hair which is not easily seen with the naked eye unless you manage to get very close to a sedentary fly.

The eggs are laid in decaying meat or other organic material on which the maggots can feed. The maggots are fully grown in a few days and when mature they move to a dry patch of soil and bury themselves below the surface to pupate. 

The cocoon takes from two to three weeks to metamorphose into an adult fly.

In autumn bluebottles visit the flowers of the carob tree. They are attracted to the flowers because of their strong smell of rotting vegetation and are important pollinators of this tree.

The bluebottle is known in Maltese as żarżura while the closely related greenbottle is known as dehbija tal-ħmieġ, These two names might have been coined by naturalists or they might have been used in the past but are not used anymore as the Maltese nowadays refer to most flies as dubbien without being aware of the various species that they meet in their everyday life.

These two species belong to a group of flies known as blow-flies. This name comes from the old English term for meat on which a fly had laid eggs, which was fly-blown. It is estimated that there are over 1,100 species of blowflies. Six of them are found n the Maltese islands. Blowflies are known carriers of disease including dysentery. 

This article was published in The Times on 26.01.11

Flies and their reputation

Flies have a bad reputation because some species are ‘harmful’ to humans even though some of these species actually do more good than harm.

Flies belong to an order known as diptera. Diptera is made up of two words, di (two) and ptera (wing). Flies have one pair of wings a feature that distinguishes them from all other insects including several species which have the word fly in their name such as mayflies, fireflies and sawflies. 

Some flies mimic other insects such as bees and wasps. This fools predatory species such as birds but the lack of a second pair of wings gives them away to any careful observer.

It is believed that there are hundreds of thousands of species of flies although half of these have not yet been identified. The situation is similar in Malta as species new to science are still being identified on a regular basis.

I love to be close to nature surrounded by wild plants and animals but mosquitoes which are flies I can live without not only because they sometimes keep me from sleeping properly but also because some species can transmit diseases such as malaria. Sand flies are just as annoying and are vectors for leishmania, a parasitic protozoan responsible for the disease leishmaniasis.

The housefly is another pest that can carry serious diseases. It is the most common of all domestic flies and is one of the most widely distributed insects. It feed on faeces, open sores, and moist decaying organic matter such as spoiled food, eggs and flesh. 

Houseflies can take in only liquid foods. They spit out saliva on solid foods to predigest it, and then suck it back in. They also regurgitate partly digested matter and pass it again to the abdomen. Because of their high intake of food, they deposit feces constantly, one of the factors that makes the insect a dangerous carrier of microbes. They can fly long distances and a fly entering through the kitchen window might have just arrived from an animal farm a considerable distance away. 

This article was published in The Times on 12.05.10