Now that the Formosan termite panic has subsided (see What lies beneath the mulch, March 13, 2006) and everyone has purchased and spread their mulch, it’s time to see what other small wonders lay beneath the mulch. Among the most common of arthropods inhabiting this nether realm are the creepy myriapods - millipedes and centipedes. These are not insects at all, far from it. They belong to a distant part of the arthropod clan in the class called Myriapoda or “many footed” arthropods. Millipedes do not really have a million legs or a thousand legs for that matter but are commonly called “thousand leggers”. Millipedes have fewer than 400 legs. The gal featured in this bug of the week had roughly 162 gorgeous legs. Unlike their insect cousins, the leg-bearing segments of millipedes usually have two pairs of legs instead of one. Millipedes are important recyclers of plant material. They eat dead things. This is exactly what is found in the rich organic medium provided by mulch. In addition to decaying vegetation, millipedes sometimes eat plant roots and leaves of small seedlings. Female millipedes lay between 20 and 300 eggs in the spring. These eggs hatch into tiny millipedes that have only a few body segments bearing single pairs of legs. As the millipede molts and grows, additional body segments are added, each with two pairs of legs. Millipedes live for two to seven years and can produce hundreds of offspring during their lifetime. This is why populations seem to explode in landscape beds. They do not bite or sting but several species secrete noxious chemicals from glands lining their body. These secretions contain cyanide producing compounds, chemical irritants, and even compounds that cause paralysis in attackers such as spiders. Chemicals released by millipedes may stain clothing or skin and be irritating. It is a good idea to wash your hands after handling millipedes. Another fascinating group of myriapods abundant in my garden are centipedes, “hundred leggers”. Just like their millipede kin their name is a misnomer because most do not have a hundred legs. Our common garden centipede like the one depicted in this bug of the week will bear 15 pairs or 30 legs when fully grown. Unlike millipedes, centipedes have a single pair of legs on each body segment. This is one good way to distinguish a centipede from a millipede. Centipedes have adopted the carnivorous life style. They are beneficial arthropods and important predators of insects and other invertebrates in your landscape beds. To capture and subdue their prey, centipedes have evolved an awesome set of appendages know as poison claws beneath their head. These powerful claws grasp their victim and inject a poison to kill it. Some very large tropical centipedes carry quite a wallop with their poison claws and capture birds, snakes, and small mammals. Although I was fortunate not to be bitten while capturing centipedes, it is generally not a good idea to capture centipedes with bare hands. Their bite is painful and similar in intensity to a bee sting. As autumn approaches and sometimes following heavy rain, millipedes exit landscape beds in large numbers and move into garages and homes. Two things can be done to reduce the chances of a myriapod invasion. First, never apply mulch so that it directly contacts your foundation. Always try to leave a barrier of bare ground of at least a foot between the mulched bed and the house. This will limit the ability of millipedes and other unwanted guests to enter your home. Also, make sure that door sweeps are in good repair to reduce the chance that millipedes will enter your home beneath basement doors.

Thomas Eisner’s book “The love of insects” by Belknap Press was used as a resource for this story and Professor Shultz helped with the identification of the arthropods. More information on the biology of myriapods can be found at the following web sites.