- Red velvet mite, magnified about five times.
Closely related to spiders, ticks and mites are tiny creatures that usually live on other creatures. Where ticks and mites liveTicks and mites are found all over the world. Ticks can be either hard or soft. Most hard ticks live in fields and woods, but a few, such as the brown dog tick, are household pests. Soft ticks generally live in the home or nest of the host. The host is the animal or plant on which a tick lives. There are about 825 types of ticks. Mites live in different habitats such as fresh water, hot springs, soil, plants, and on and in animals. Parasitic mites (those that live on other animals) may live in the nasal passages, lungs, stomach, or deeper body tissues of animals. There are about 20,000 species of mites. Physical characteristicsAdult ticks range in size up to slightly more than 1 inch (25 millimeters), but most species are about 1/2 inch long (13 millimeters or less). Most adult ticks have four pairs of legs. Some ticks are covered with stiff hairs, and they may or may not have eyes. Hard-bodied ticks have many hardened plates on their bodies. Their body is divided into two segments. They are flat when unfed but bloat up and become rounded as they eat. Soft-bodied species have only a few plates. Ticks can be distinguished from mites by the presence of a sensory pit, called Haller's organ. This is located on the end segment of the first pair of legs. Mites are small and often invisible to the naked eye. The smallest is about 4/1000 inch (0.1 millimeter) in length and the largest is about 1/4 inch (6 millimeters) in length. Like ticks, they usually have four pairs of legs. In general, mites breathe by means of tracheae, or air tubes. In many species, however, respiration takes place through the skin. For the most part, mites have a rounded body on which there are a number of long bristles. There is little sign of a head, though they have sucking mouthparts. Some have eyes, while others are blind. Life cycleTicksTicks have a life cycle of three to four years. Ticks require blood for their development and reproduction. Hard ticks, such as the American dog tick, attach to their hosts and feed continuously for several days. When full, the female drops off, lays thousands of eggs, and dies. The eggs hatch after about two weeks into six-legged larvae. The larvae move up on blades of grass and wait for a suitable host, usually a rodent. After feeding themselves with the host's blood, they drop off and grow into eight-legged nymphs. Nymphs, also known as seed ticks, remain inactive until the following spring. Then they wait in high grasses for a suitable host, usually a dog or human. If they cannot find a host they die. If they find a host, they feed on it. They fall off once again and emerge as adult males or females. The adult remains inactive throughout the winter. It then attaches itself to another host. It feeds and breeds in the following spring and then dies. Sometimes a tick has to wait for a long time for a host. It is able to go without a meal for months or even years without suffering harm. Soft ticks feed from time to time and lay several batches of eggs. The young ticks pass through similar stages as hard ticks, but they carry on their developmental cycles in the home or nest of the host rather than in fields. MitesThe young mite is also called a nymph. It has only three pairs of legs when it hatches. It molts, or casts off its outer covering, several times while growing into an adult. In the process it develops the fourth pair of legs. PestsThere are several ways in which ticks are harmful to their hosts. Many of the tick species transmit diseases to people and animals. Some ticks also damage crops. Ticks have germs in their stomachs. While they are sucking blood, these germs may pass into the wound and cause diseases in the host. Also, when a tick bites a host, it causes a break in the skin. This makes it easy for germs to enter the host and cause infections. Hard ticks harm the host by emitting neurotoxins, or nerve poisons. These poisons can cause gradual paralysis and eventually death if the tick is not properly removed in time. Soft ticks also are carriers of diseases. Mites also transmit plant and animal diseases. Parasitic mites attack humans. Grain mites not only damage stored grains but also cause skin irritations in those who handle such products. Itch mites burrow into the skin of humans, dogs, pigs, sheep, and goats, causing injury. |