Millipedes and Centipedes

Both millipedes and centipedes are many-legged arthropods with worm-like bodies. Millipedes are slower moving, omnivores whilst centipedes are more rapidly-moving predators. Neither group are serious pests but occasionally present problems in the home.

Common types

Two of the most frequent millipedes found in houses are Parajulus venustus and P. immpressus.

They are brown, 1.5 inch long millipedes which hide beneath objects on damp soil during the day. The garden millipede, Oxidus gracilis is found throughout the Southwest and in greenhouses in other areas.

Biology

Millipedes

The fossil record indicates that millipedes are one of the oldest land animals; one fossil is dated to 430 million years ago. They belong to the class Diplopoda, which consists of 15 orders containing about 10,000 names species and a predicted total of 80,000 species. The principal orders are the Sphaerotheriidae (pill millipedes), Polydesmida (flat millipedes), Spirostreptida (round millipedes) and Spirobolida (round millipedes). Millipedes occur throughout the USA and most of other parts the world. They have worm-like bodies which are round in cross section.

One of their most distinguishing characteristics is their many legs; 30 to more than 90 pairs in adults. Each body segment (actually two fused segments) bears two pairs of legs, the exception being their first 3-4 segments and the last 3, which either lack them or bear only one pair. Millipede antennae are 7-segmented and their eyes are simple (known as ocelli), clustered in two areas on either side of the head.

The millipedes life cycles involves internal fertilization, after which the female lays eggs in clusters of 20-300 in the soil, sometimes within capsules. The eggs hatch after several weeks and first instar larvae emerge, with 7 body segments and three pairs of legs. Seven to ten molts follow, each resulting in the addition of more segments and legs.

Molting usually stops when adulthood is reached, which is often in the second year, although some species require 4-5 years. Millipedes are scavengers, feeding upon damp and decaying wood, other rotting vegetable material including deciduous leaves and shoots. They will occasionally feed upon dead insects, snails and earthworms. During dry periods they may feed upon live plants to obtain moisture.

Millipedes will also feed upon their molted skins to retrieve the calcium in them. Millipedes requite high moisture levels and are therefore found in piles of decaying plant material such a leaf litter, grass clippings and garden mulch. They are largely nocturnal, doubtless enjoying the generally higher humidities typical of night time as well as protection from predators that hunt by day.

Centipedes

Centipedes belong to the Class Chilopoda and occur throughout the USA and the world., with over 3,000 species known. The Chilopoda consist of five orders. Centipedes of the Order Craterostigmomorpha are only found in Australia and New Zealand. The Geophilomorpha are long and thin tend to burrow in soil and leaf litter. The Lithobiomorpha is the largest order, with approximately 1800 species.

They range in size from 1/4 to 1 ½ inches in length and the rear-most pair of legs are greatly elongated. The Scolopendromorpha has approximately 600 species, including the world’s largest centipede; Scolopendra giganteus, which can be up to 10 ½ inches long. This species is native to the West Indies and South America, but other, still large, members of the genus do occur in the southwestern states.

Most centipedes in the US are far smaller and the last order, the Scutegeromorpha contains the species which is most commonly found in the American home: Scutigera coleoptrata, the common house centipede. This species originated from Mexico.

Health issues

Millipedes

“Several species of millipedes emit a foul smelling fluid from openings along the sides of their bodies. In certain species, this fluid contain hydrocyanic acid, iodine and quinone; it is toxic to some arthropods and small animals. This fluid can cause blistering of human skin.

Millipedes are rarely if ever serious pests to the householder. When they do become pests indoors, control is often best achieved by modifying the sites where they are found by eliminating the damp areas they need to survive. When millipedes are pests out of doors, four approaches may be used, all aimed at reducing moist areas.

Firstly, clear away piles of debris such as leaves, brushwood, mulch and rocks. Ventilate crawl spaces. Secondly, de-thatch lawns since dense thatch traps moisture. Thirdly, mow and edge lawns to speed up drying. Finally, water lawns in the early morning so that they have all day to dry. If these simple measures are insufficient, insecticides may be applied to basement walls, beds of flowers and ornamental plants, unfinished basements and crawl spaces.

Wettable powders and micro-encapsulated products are usually best except in crawl spaces where dusts maybe used. Given the millipedes’ dependance upon dampness, insecticides should only be used as a last resort. During mass migrations, residual treatment have little effect owing to the brief exposure of the millipedes to the treated substrates. Using a shop-vac (a vacuum if indoors) to remove the invaders is more effective.

Centipedes

Centipedes are primarily carnivorous, feeding upon insects, such as fruit flies, crickets and cockroaches, spiders, earthworms, isopods and other small creatures. This diet means that they can be beneficial residents of one’s home. Occasionally centipedes will feed upon plants and cause damage.

As with millipedes, centipedes are most often found in damp places such as under loose tree bark, wood piles, under stones and logs, piles of leaves and grass clippings and similar situations. They are most active at night. Centipedes rarely enter houses, except for Scutigera coleoptrata, which is often found in basements, bathrooms, damp closets and pot plants.

Centipedes only rank as pests because of their ability to inflict painful, poisonous bites with their maxillipeds. The larger Scolopendra species can deliver a very painful bite and should be treated with respect. Centipedes occasionally attack and damage plants, probably for their moisture.

Centipedes  and Millipedes control

Millipedes

Millipedes are rarely if ever serious pests to the householder. When they do become pests indoors, control is often best achieved by modifying the sites where they are found by eliminating the damp areas they need to survive. When millipedes are pests out of doors, four approaches may be used, all aimed at reducing moist areas. Firstly, clear away piles of debris such as leaves, brushwood, mulch and rocks. Ventilate crawl spaces. Secondly, de-thatch lawns since dense thatch traps moisture. Thirdly, mow and edge lawns to speed up drying.

Finally, water lawns in the early morning so that they have all day to dry. If these simple measures are insufficient, insecticides may be applied to basement walls, beds of flowers and ornamental plants, unfinished basements and crawl spaces. Wettable powders and micro-encapsulated products are usually best except in crawl spaces where dusts maybe used. Given the millipedes’ dependance upon dampness, insecticides should only be used as a last resort.

During mass migrations, residual treatment have little effect owing to the brief exposure of the millipedes to the treated substrates. Using a shop-vac (a vacuum if indoors) to remove the invaders is more effective.

Centipedes

Control of centipedes is similar to that for millipedes. The best approach is to dry out the affected areas since centipedes can only survive in damp conditions. Therefore accumulations of leaves, mulch, brush wood, logs, stones etc should all be removed from the affected area. Firewood should be stored above ground to allow ventilation. For indoor infestations, a vacuum cleaner is very useful. These simple measures will minimize, or even eliminate, the need for pesticides.

If the above measures do not work, judicious use of appropriately labeled pesticides is needed. Residual treatment of building foundation walls, basements, flower and ornamental beds, crawl spaces and similar areas is needed. Wettable powders and micro-encapsulated products are best. Eliminating the centipedes’ prey source (insects, spiders, worms etc) will also help.