Scutigera coleoptrata (one of several species commonly known as the house centipede), is a typically yellowish-grey centipede with 15 pairs of legs. Originally endemic to the Mediterranean region, the species has spread to other parts of the world, where it usually lives in human homes. It is an insectivore; it kills and eats arthropods such as insects and arachnids. It is also known as a "mustache bug" in certain cultures, and in many places of America are (mistakenly) referred to as silverfish.

Morphology

S. coleoptrata is 25 mm (1 in) to 50 mm (2 in) in length and has up to 15 pairs of remarkably long legs. These delicate legs are attached to a rigid body. This enables it to reach surprising speeds of up to 0.4 metres per second (1.3 ft/s)^[1] running across floors, up walls and along ceilings. Its body is yellowish-grey and has three dark-colored dorsal stripes running down its length; the legs also have dark stripes. Unlike most other centipedes, house centipedes and their close relatives have well-developed, faceted eyes. S. coleoptrata has developed automimicry in that its hind legs present the appearance of antennae. When at rest, it is not easy to tell its front from its back.

Reproduction and development

House centipedes lay their eggs in spring. In a laboratory experiment of 24 house centipedes, an average of 63 and a maximum of 151 eggs were laid. Like in many other arthropods, the larvae look like miniature versions of the adult, albeit with fewer legs. Young centipedes have four pairs of legs when they are hatched. They gain a new pair with the first molting, and two pairs with every of their five subsequent moltings. Adults with 15 pairs of legs retain that number through three more molting stages (sequence 4-5-7-11-13-15-15-15-15 pairs)^[2]. They live anywhere from three to seven years, depending on the environment. They can start breeding in their third year. For mating the male and female circle around each other. They initiate contact with their antennae. The male deposits his sperm on the ground and the female then uses it to fertilize her eggs. Some report that the eggs are deposited in the ground and covered with plant matter. Scutigera coleoptrata was observed providing parental care. The female lies on her side cradling her clutch of eggs, and later the larvae. This behavior was reported to proceed for several weeks. The female applies an antifungal secretion by mouthing the eggs.

Behavior and ecology

Closeup of the head showing modified legs

House centipede stalking a spider

House centipedes feed on spiders, bedbugs, termites, cockroaches, silverfish, ants, and other household arthropods. They administer venom through modified legs. These are not part of their mandibles, so strictly speaking they sting rather than bite. They are mostly nocturnal hunters. Despite their developed eyes they seem to rely mostly on their antennae when hunting. Their antennae are sensitive to both smells and tactile information. They use both their mandibles and their legs for holding prey. This way they can deal with several small insects at the same time. To capture prey they either jump onto it or use their legs in a technique described as "lassoing". Using their legs to beat prey has also been described.^[3] In a feeding study, S. coleoptrata showed the ability to distinguish between possible prey. They avoid dangerous insects. They also adapted their feeding pattern to the hazard the prey might pose to them. For wasps, they retreat after applying the venom to give it time to take effect.^[3] When the centipede is in danger of becoming prey itself, it can detach any legs that have become trapped.

Habitat

Outdoors, house centipedes prefer to live in cool, damp places. Centipede respiratory systems do not provide any mechanism for shutting the spiracles. That is why they need an environment that protects them from dehydration and excessive cold. Most live outside, primarily under large rocks, piles of wood and especially in compost piles. Within the home, these centipedes are found in almost any part of the house. Most commonly, they are encountered in basements, bathrooms and lavatories, that tend to be humid, but they can also be found in drier places like offices, bedrooms and dining rooms. The greatest likelihood of encountering them is in spring, when they come out because the weather gets warmer, and in autumn/fall, when the cooling weather forces them to find shelter in human habitats.

Distribution

Scutigera coleoptrata is indigenous to the Mediterranean region, but it has spread through much of Europe, Asia, and North America. It is thought to have first been introduced in America in Mexico and Guatemala. In the United States, it has spread from the southern states. It reached Pennsylvania in 1849, New York in 1885, and Massachusetts about 1890, West Virginia and its distribution now extends westward to the California coast and reaches north into Canada (Lewis 1981). In South Africa, they have been found in the Western Cape, in and around Cape Town (sightings have been reported in Pinelands and Gordon's Bay) and also in KwaZulu-Natal, in the city of Pietermaritzburg. In Japan, these creatures are referred to as gejigeji.^[4] They have also been found in eastern and south-eastern Australia, from Sydney to Tasmania as well as in New Zealand.

Biological details

The faceted eyes of Scutigera coleoptrata are sensitive to daylight as well as very sensitive to ultraviolet light.^[5] They were shown to be able to visually distinguish between different mutations of fruit flies. How this ability fits with its nocturnal lifestyle and underground natural habitat is still under study. They do not instantly change direction when light is suddenly shone at them, but retreat to a darker hiding spot. Some of the plates covering the body segments fused and became smaller during the evolution to S. coleoptrata's current state. The resulting mismatch between body segments and dorsal plates (tergites) is the cause for this centipede's rigid body.

Tergites 10 and 11 are not fully developed and segment 18 does not have a sternite. This model deviates from descriptions by Lewis who identified only 7 tergites and 15 segments.^[6]

Another feature that sets S. coleoptrata apart from other centipedes is that their hemolymph was found to contain proteins for transporting oxygen.

The mitochondrial genome of Scutigera coleoptrata has been sequenced. This opened up discussions on the taxonomy and phylogeny of this and related species.^[7]

Interaction with humans

Unlike its shorter-legged but much larger tropical cousins, S. coleoptrata can live its entire life inside a building, usually the ground levels of homes. They are generally considered harmless to humans.^[8] Bites are not common, and the jaws of most house centipedes are not strong enough to penetrate human skin. Stings are generally no worse than a bee's sting, with its venom causing redness and mild to severe swelling.^{[9] [10]}

Techniques for eliminating centipedes from homes include drying up the areas where they thrive, eliminating large indoor insect populations, sealing cracks in the walls, and seeking the assistance of an exterminator.

References