Collaboration: Royal Entomological Society

Insects are invertebrate animals, that is, animals having an external skeleton or hardened outer shell. All insects have six legs (three pairs) and many have two pairs of wings. Sometimes the number of wings is reduced to one pair. This occurs where a pair is structurally modified e.g. the front pair of wings in beetles (Coleoptera) are modified into hardened wing covers called elytra; the posterior pair of wings in flies (Diptera) are modified into gyrating balancing organs called halteres. 

There are very many insects - potentially 9 out of every ten organisms on Earth are insects. Just over one million insects have been described to date and there may be as many as 10 million on Earth. So, it is no easy matter to identify an insect. 

The first step is to be sure it is an insect (check that there are only three pairs of jointed, locomotory legs). The find which Order the insect belongs to: there are 29 different Orders of insects dominated by four hugely diverse Orders: beetles (Coleoptera), flies (Diptera), moths (Lepidoptera) and ants, bees and wasps (Hymenoptera). 

It is usually necessary to ask a specialist if an accurate species identification is needed. Contact FlyEvidence.co.uk for more help.

All insects have six legs - that is three pairs of legs.

This differentiates them from other Arthropods, such as spiders, ticks and mite that all have  four pairs of legs (eight in total) and all crustacea (crabs, shrimp etc) which have at least five pairs of legs.

Insect bodies have three sections: the head,  the thorax and the abdomen.

Insects have one pair of antennae (or feelers).

One pair of compound eyes (and sometimes other eyes too).

Insect life cycles are divided into nymphal or larval growing stages and adult reproductive stages, between which some insects have a pupa stage in which the larval body re-arranges to form the adult insect.

True bugs (Hemiptera) have multi-segmented sucking mouthparts and four wings. These are aphids, cicadas, stink bugs, bed bugs and water bugs.

Flies have only two wings - the hind wings are reduced to balancing organs called halteres. Flies and creatures like beetles, butterflies, bees, wasps and ants are often called bugs, but this is a poor name for them. Along with bugs, these are all insects. 

There are also many non-insect species that are loosely called bugs, such as millipedes, centipedes, ticks, mites and spiders. But of course the word ‘bug' is also used to describe pathogens that cause disease (loosely 'germs’) or things that cause computers to go wrong, such as viruses and Trojans, or simply bad coding.

Relative to the volume of blood in the host that a female mosquito feeds from, the portion of blood taken up by the mosquito is extremely small; despite the irritation being so big. 

Aedes aegypti draws approximately 0.002ml of blood. A human has about 4-5 litres of blood (that is a ratio of 2 x 10^6). It’s a minute amount that the female mosquito draws off.

 For viral diseases such as HIV, the levels of viraemia are too low by about six orders of magnitude for successful insect transmission. In other words there isn’t a high enough proportion of viral cells to blood sub-sample taken by the mosquito for effective transmission to occur.

Not only that, the virus does not invade the mosquito salivary glands and hence does not get transmitted along with anti-coagulant when the mosquito bites.

Probably not.  It is untested. Nevertheless, when mosquitoes bite, they inject an anti-coagulant from their salivary glands. Blood from a previous victim is in the crop (part of the digestive tract) and is not injected along with the anti-coagulant. There may be traces of blood on the outer parts of the mouthparts, but these are likely to be too minimal to transfer the virus.

 For the successful transmission of a disease parasite such as malaria plasmodia, which are very small, via  a small amount of the host blood fed on by a mosquito, the parasite has to be very abundant in the host blood. The plasmodia are so small (100-600 nm) that they invade the liver and blood cells in the host and breed there!

To reach high abundance in the host blood, the plasmodia proliferate to enormous numbers, flooding the blood with parasites, which is what sets off the body reaction leading to fever. The invasion of parasite into the blood is known as parasitaemia.

Within the mosquito, the plasmodia travel from the gut to the salivary glands and hence are transmitted into a new host when the mosquito feeds

For viral diseases such as HIV and coronavirus, the levels of viraemia (the medical condition where viruses enter the bloodstream) are too low by about six orders of magnitude for successful insect transmission. In other words there isn’t a high enough proportion of viral cells to blood meal taken by the mosquito for effective transmission to occur.

The dangers posed by use of a synthetic chemical such as DEET, is regarded far lower than contracting a disease such as malaria. So if you are visiting an area of high mosquito activity, or of known malaria endemism, it is better to be safe using a chemical, than to contract the disease.

DEET (N,N-diethyl-3-methylbenzamide or C12H17NO) is the most common active ingredient in insect repellents. Although health studies have shown no significant harm to humans, anyone exposed to large amounts, or using DEET for prolonged periods, should be carefully monitored for side effects.

Always read the label; avoid contact with eyes and broken or sensitive skin; take care (and think twice) when using on children.

It’s a brilliant name for a product, but they call it octenol instead!

Mosquitoes and biting flies are attracted to (among other things) the carbon-dioxide that mammals breathe out. An octenol trap uses carbon-dioxide and the chemical octenol to lure mosquitoes and other biting flies (such as midges) into a trap, where they are then disposed of by electric current. 

The efficiency of the traps can be increased by using airflow and thermal or color-visual properties which increase the attraction to the insects.