Cockroach relationship with Humans

Relationship with Humans                                                                 

In research and education

Because of their ease of rearing and resilience, cockroaches have been used as insect models in the laboratory, particularly in the fields of neurobiology, reproductive physiology and social behavior. The cockroach is a convenient insect to study as it is large and simple to raise in a laboratory environment. This makes it suitable both for research and for school and undergraduate biology studies. It can be used in experiments on topics such as learning, sexual pheromones, spatial orientation, aggression, activity rhythms and the biological clock, and behavioral ecology. Research conducted in 2014 suggests that humans fear cockroaches the most, even more than mosquitoes, due to an evolutionary aversion.

As pests

The Blattodea include some thirty species of cockroaches associated with humans; these species are atypical of the thousands of species in the order. They feed on human and pet food and can leave an offensive odor. They can passively transport pathogenic microbes on their body surfaces, particularly in environments such as hospitals. Cockroaches are linked with allergic reactions in humans. One of the proteins that trigger allergic reactions is tropomyosin. These allergens are also linked with asthma. About 60% of asthma patients in Chicago are also sensitive to cockroach allergens. Studies similar to this have been done globally and all the results are similar. Cockroaches can live for from a few days to up to a month without food, so just because no cockroaches are visible in a home does not mean they are not there. Approximately 20-48% of homes with no visible sign of cockroaches have detectable cockroach allergens in dust.

Cockroaches can burrow into human ears, causing pain and hearing loss. They may be removed with forceps, possibly after first drowning with olive oil.

Control

Many remedies have been tried in the search for control of the major pest species of cockroaches, which are resilient and fast-breeding. Household chemicals like sodium bicarbonate (baking soda) have been suggested, without evidence for their effectiveness. Garden herbs including bay, catnip, mint, cucumber, and garlic have been proposed as repellents. Poisoned bait containing hydramethylnon or fipronil, and boric acid powder is effective on adults. Baits with egg killers are also quite effective at reducing the cockroach population. Alternatively, insecticides containing deltamethrin or pyrethrin are very effective. In Singapore and Malaysia, taxi drivers use pandan leaves to repel cockroaches in their vehicles.

Few parasites and predators are effective for biological control of cockroaches. Parasitoidal wasps such as Ampulex wasps sting nerve ganglia in the cockroach's thorax, temporarily paralyzing the victim, allowing the wasp to deliver an incapacitating sting into the cockroach's brain. The wasp clips the antennae with its mandibles and drinks some hemolymph before dragging the prey to a burrow, where an egg (rarely two) is laid on it. The wasp larva feeds on the subdued living cockroach. Another wasp which is considered a promising candidate for biological control is the ensign wasp Evania appendigaster which attacks cockroach oothecae to lay a single egg inside. Ongoing research is still developing technologies allowing for mass-rearing these wasps for application releases.

Cockroaches can be trapped in a deep, smooth-walled jar baited with food inside, placed so that cockroaches can reach the opening, for example with a ramp of card or twigs on the outside. An inch or so of water or stale beer (by itself a cockroach attractant) in the jar can be used to drown any insects thus captured. The method works well with the American cockroach, but less so with the German cockroach.

A study conducted by scientists at Purdue University concluded that the most common cockroaches in the US, Australia and Europe were able to develop a “cross resistance” to multiple types of pesticide. This contradicted previous understanding that the animals can develop resistance against one pesticide at a time. The scientists suggested that cockroaches will no longer be easily controlled using a diverse spectrum of chemical pesticides and that a mix of other means, such as traps and better sanitation, will need to be employed.

As food

Although considered disgusting in Western culture, cockroaches are eaten in many places around the world. Whereas household pest cockroaches may carry bacteria and viruses, cockroaches bred under laboratory conditions can be used to prepare nutritious food. In Mexico and Thailand, the heads and legs are removed, and the remainder may be boiled, sautéed, grilled, dried or diced. In China, cockroaches have become popular as medicine and cockroach farming is rising with over 100 farms. The cockroaches are fried twice in a wok of hot oil, which makes them crispy with soft innards that are like cottage cheese. Fried cockroaches are ground and sold as pills for stomach, heart and liver diseases. A cockroach recipe from Formosa (Taiwan) specifies salting and frying cockroaches after removing the head and entrails.

In traditional and homeopathic medicine

In China, cockroaches are raised in large quantities for medicinal purposes.

Two species of cockroach were used in homeopathic medicine in the 19th century.

Conservation

While a small minority of cockroaches are associated with human habitats and viewed as repugnant by many people, a few species are of conservation concern. The Lord Howe Island wood-feeding cockroach (Panesthia lata) is listed as endangered by the New South Wales Scientific Committee, but the cockroach may be extinct on Lord Howe Island itself. The introduction of rats, the spread of Rhodes grass (Chloris gayana) and fires are possible reasons for their scarcity. Two species are currently listed as endangered and critically endangered by the IUCN Red List,  Delosia ornata and Nocticola gerlachi. Both cockroaches have a restricted distribution and are threatened by habitat loss and rising sea levels. Only 600 Delosia ornata adults and 300 nymphs are known to exist, and these are threatened by a hotel development. No action has been taken to save the two cockroach species, but protecting their natural habitats may prevent their extinction. In the former Soviet Union, cockroach populations have been declining at an alarming rate; this may be exaggerated, or the phenomenon may be temporary or cyclic. One species of roach, Simandoa conserfariam, is considered extinct in the wild.