Insects as Pests
The majority of insects have wings in the adult stage and move around mainly by flying. Some insects, such as cockroaches, have wings but are reluctant flyers, preferring to crawl to find food and shelter. Termites and ants are mainly wingless, so most of their behaviour involves crawling, and produce ‘reproductives’ that are temporarily winged during a short breeding season.
Other insects, such as the flea and louse, are wingless and can only crawl or jump to move around. Crawling insects here refers to insects that are perceived as pests mainly due to their crawling behaviour.
Insects are distinguished by having an exoskeleton with a three-part body, consisting of: a head with compound eyes, a pair of antennae and very variable mouthparts; a thorax with six legs and often one or two pairs of wings; and an abdomen.
Most insects go through a life cycle starting with eggs and a series of developmental stages or moults, before they reach their adult stage. This is typically egg, larva (eg caterpillar, maggot), pupa (often sealed in a cocoon) and adult, which often has wings.
Other arthropods, the arachnids (spiders, ticks, mites, scorpions) and the Myriapods (centipedes) are all wingless so only move around by crawling. They are characterised by having two body sections, the cephalothorax (fused head and thorax) and abdomen with eight legs. Ticks and mites have a similar life cycle to insects, with egg, larva, nymph and adult stages. Spiders and scorpions produce eggs and progress through larval stages in the egg, hatching as small immature adults that have to go through several moults to grow to the adult size. These are included with the crawling insects for convenience.
Insects as pests
Crawling insects and arachnids are regarded as pests for a number of reasons:
bites cause pain and swelling from the body’s immune reaction to the ‘foreign material’ from the insect/arachnid mouth injected with the bite;
stings cause pain and an allergic reaction from the venom injected into the skin.
insect bites can transmit a large number of serious bacterial, viral and parasitic diseases to humans and domestic animals;
allergens produced by infestations in the home can cause asthma;
contamination of food, water and surfaces by mechanical transmission of diseases, in homes and businesses;
consumption of and damage to stored food products in homes and businesses;
damage to fabric products such as clothing and furniture;
damage to wooden structures and products.
Businesses, organisations and homeowners need to control insect pests to:
Prevent damage: insects can damage packaging and goods such as clothing and furniture.
Prevent and eliminate contamination: food in storage or processing is subject to insect attack or contamination.
Prevent disease: insects can carry a large number of diseases that affect humans and animals, both farm animals and pets.
Conform with the law: laws and regulations require control of insects in property, especially for food handling, and health and safety. Failure to comply can lead to prosecution.
Prevent financial loss: caused by damage to goods, compensation, litigation and loss of trade.
Prevent loss of reputation and goodwill: the presence of insects on commercial premises and damaged goods are unacceptable to other businesses and the public.
Ants are generally more of a nuisance than a danger, though they can sting and a can few bite. Different species of ant sting with a range of chemicals, including formic acid, alkaloids and piperidines.
Ants can invade homes, other buildings, and gardens to forage for food and build nests. They are not known to transmit diseases. Out of the thousands of species of ant worldwide, there are only a few ant species that are regarded as pests in each country.
Bed bugs bite to feed on blood, often producing an itchy bump on the skin. They tend to form colonies in small hidden places in bedrooms and furniture where humans are still for long periods. These include bed frames, carpets and underlay, drawers and cupboards. You are most likely to pick up bedbugs from a hotel where they can crawl into your luggage or clothing. However, they are not known to transmit diseases.
Cockroaches carry a large number of disease-causing organisms that can contaminate food and surfaces, including Salmonella. They also produce particles that produce allergic reactions, causing asthma. They are one of the most serious pests of homes, food processing factories, restaurants, and healthcare facilities worldwide.
Fleas are usually brought into contact with humans by pets and wild animals, including cats, dogs, rats, mice, foxes, birds, and rabbits. There are several species, each preferring a particular animal host, but will attempt to feed on other hosts, including humans before dropping off. Fleas can also transmit the serious bacterial diseases: murine typhus and plague.
There are three types of human louse, the head louse, body louse and crab louse. Head lice can be passed from person to person by close contact and infest anyone with hair. In developed countries they most commonly affect children.
The body louse is the same species as the head louse but lives mainly in clothing and is spread by close contact with someone infested, or infested clothing and bedding. These are generally more of an irritant than a danger, causing itching and distress.
Both can carry the serious diseases epidemic typhus, endemic/murine typhus, and relapsing fever, which tend to break out in poor living conditions such as caused by war and famine.
The crab louse is a distinct species from the other types and is spread by close contact. It is usually found in coarser body hair, such as pubic hair and eye lashes. This is also more of an irritant than a danger.
The caterpillars of these moths can cause extensive defoliation of trees. They are also a public health hazard because their long hairs contain an irritating chemical that causes rashes and occasionally more severe allergic reactions. This can occur from touching the caterpillars and from loose hairs blown in the wind.
The Oak processionary moth is native to southern Europe but has migrated northwards to Germany and the UK. The Pine processionary moth is native to southern Europe and North Africa. Careful removal of caterpillars and pheromone traps to catch adults are used to prevent outbreaks.
Stored product insects
A wide variety of insect species can infest food in the journey from the field to the consumer:
food processing plants,
in the home.
They reduce the quantity of saleable goods, causing economic losses to farmers and businesses, and cause reputational damage by affecting the quality of goods. Crawling insects that affect stored food include many species of weevil and other beetles (which have thousands of species), and a few species of mite (which are arachnids).