Pests of the home & landscape

July 18, 2000
Millipedes

A few millipedes can always be around homes; however, at times thousands of these animals will migrate from one area to another. When this happens, numbers can increase dramatically. As they crawl about, they will enter houses, accumulate on carports, and fall into swimming pools.

Description and Habits

Millipedes are elongate with many body segments and legs. The first segment behind the head has no legs, the next four segments have one pair of legs, and the remaining segments (except for the last) have two pairs of legs. Body length will vary from one half inch to four inches, depending on species. One of the most common species (Oxidus gracilis) is one inch to one and one half inches long. The body is rounded on top and flat on the bottom and the integument is hard, similar to that of the beetles.

Millipedes are herbaceous and feed mainly on decaying plant material. There have been some reports of damage to tender green plants; however, the mouthparts consist of combs and scrapers which are ideal for feeding on soft decaying materials. These animals are inactive during the day and may be found in forest floor litter, mulched flower beds, dense thatch in lawns or in deep grass along drives and sidewalks. Movement and feeding occur at night. Their nocturnal habit is related to water conservation. Millipedes do not have a lipid layer over the integument as do insects, nor can they close the tracheal openings. These factors make the animals very susceptible to water loss if they are not in a moist environment.

Growth is by a gradual metamorphosis. Eggs are deposited in the soil in groups ranging from 20 to 300 eggs per cluster. At an average temperature of 75 degrees F, the eggs hatch in five to ten days. In one study conducted in Florida, it took the greenhouse millipede an average of 153 days to go from egg to adult.

Migrations

Migrations may be caused by:

  • Population Pressure. As numbers increase in an area, the competition for food and harborage forces some part of the population to seek other sites.
  • Destruction of Habitat. Movement may occur during construction. As habitat is destroyed, the millipedes will seek other sites.
  • Standing Water. After long periods of rain, standing water may force millipedes from low lying areas.

Although any of the above may be involved, population pressure is probably the main reason for mass movements of millipedes. Movement is always at night. A person may clean up in the afternoon and by the next morning hundreds have again accumulated. Another problem that one may encounter is that some may think that they are trying to get in the house and that's not the case-it's just that the house gets in their way and invariably a few will get into the house. They may enter though weep holes, around service lines or around loose fitting windows or doors. Once they enter the house, they will soon die due to the dry conditions which occur in most air conditioned buildings. Although there may some odor associated with these animals, the number one problem is probably one of nuisance-just the thought of thousands of anything occurring on ones property is somewhat unsettling. In one case, a family had been living at a location south of Tupelo for seven to eight years and had never seen a millipede, much less several thousand a night. Then a migration started, and the homeowners cut every tree and shrub around their property in an attempt to reduce the breeding areas available to millipedes.

Controls

Insecticides such as Sevin or diazinon can be used round the outside foundation wall and these applications will kill a lot of millipedes; however, within 24 to 48 hours they will have returned. This is one of those situations that what nature has created nature will have to cure. Once the population in an area has reached a balance the movement will cease. This may take several weeks and it may occur for some period of time during the spring of the following year.

 

Dr. James Jarratt
Extension Entomologist

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