Sunday, March 1, 2015

Red Velvet Mite

Red Velvet Mites in the family Trombidiidae include more than a 1,000 species Worldwide. They are classified as arachnids, but differ from spiders in many ways. Spiders possess 6 or 8 eyes, mites only have 2. Spiders have two body segments, whereas mites have only one. Mites also have a unique leg arrangement. There are two legs located in four separate sections on the underside of their body. There are many other differences which are too technical for me, but suffice it to say, while related, they are like distant cousins on the spider family tree.

They are sometimes called rain bugs as they are active after heavy rains especially in the early spring or fall. The one pictured here was found after a spring rain while mushroom hunting. It was actively hunting for prey on a rotting log. I knew it was a velvet mite, but had no idea its identity beyond that. It is next to impossible to differentiate one species from another without a microscope with exception to a few Palearctic species like the giant red velvet mite (Trombidium grandissimum). This particular red velvet mite is found in India, and may reach lengths up to 1/2 inch. This species is a true giant in the mite world where most species are nearly microscopic in size. They get their common name of red velvet mite from the fine red hairs all over their body which resembles velvet and gives them the ability to sense their surroundings. In addition to using those fine body hairs, they also sense their environment through vibrations and pheromone responses. Their front legs aid in guiding them through the habitats where they live by acting as a sensory organ. Having only 2 eyes gives them a serious disadvantage in the eyesight department, so instead they rely on delicate vibrations and pheromones that cue them in on food and mates. The bright red color warns potential predators that they taste bad and therefore they have few enemies with exception to their own kind which may cannibalize them. The 2nd stage nymphs have also been known to parasitize them.

Even though they taste terrible, it seems humans have found a use for them in medicine. Oils from some species, like the Giant Red Velvet Mite are used in traditional medicine to treat paralysis. In some cultures they are used as an aphrodisiac, earning them the name of "Indian Viagra." They are also used in a treatment to improve the immune system. Like any creature that finds itself useful to humans it can often be removed from the environment in such drastic numbers as to affect the overall balance of the ecosystem where they were found. Red Velvet Mites are an integral part of the ecosystem as a biological control agent feeding on harmful arthropods such as spider mites, spring cankerworm, cabbage moth, lace bug, and other arthropods that may damage crops. As nymphs they act as ecto-parasites and also control many harmful insects.

Mating between red velvet mites is an involved process which includes the male performing a bit of a dance to impress the female. He will deposit a spermatophore nearby on a small twig, piece of bark, or blade of grass. He then forms a chemical trail made of silk that he guide her across, essentially walking her to his "gift." If she is receptive to his advances she will position her body on top of the spermatophore and remain there until she has taken all his sperm into her body, becoming impregnated. If another male happens upon this scent trail he will follow it to the spermatophore and break it open, he will then leave his own spermatophore in place of his competitors. Essentially ensuring his genes are passed on without all the work of finding the female, dancing his 8 tiny legs off, and walking his female to his present. What a lazy little trickster!

The female will lay her eggs, from 60-100,000 depending upon species, in the soil, leaf litter or other organic matter. When the eggs hatch the newly born pre-nymphs stay very close to the area where they were born. After a few days they leave and take on the life of an ecto-parasite feeding on various arthropods, including grasshoppers, crickets, arachnids, aphids, etc. (pictured: mites feeding on Harvestman)

In most case their feeding does not kill the host, but in some cases their numbers are so large the host cannot survive. The next stage, called protonymphs   are calyptostatic and develop inside the cuticle of the larvae. They lie inactive like a pupa. After emerging from the cuticle of the host they now possess eight legs and are more active hunters, searching out prey, rather than attaching themselves to a host. They generally complete their lifecycle and become adults in the fall. It is common to see them after the first heavy rain in autumn. Any eggs that hatch in the late summer or early fall will not have time to complete their lifecycle to adulthood. Those individuals will overwinter and complete their lifecycle the next year or in some cases the following year.

These fuzzy little arachnids are common, yet rarely seen, brightly colored, yet harmless to humans, voracious predators, yet excellent biological pest control. When the spring rains return, head to the timber and search for these unique, fascinating, brightly colored arachnids as they hunt for food and mates among the forest floor. These tiny mites are a true treasure of the woodlands.

1 comment:

  1. A interesting critter. I think I see them more in the spring ,especially when I sit down in deep woods looking for that hidden mushroom. Nice to hear from you.