(1) Many mites are parasites of birds and mammals.
(2) They can be ectoparasites, feeding on the outer skin, or endoparasites, feeding on the underlying tissues. The ectoparasites live on the host's body surface, while the endoparasites dig tunnels under the host's skin in which they live and reproduce.
(3)While some parasitic mites transmit disease organisms, many cause diseases themselves. These include scabies and contagious skin diseases characterized by inflammation, irritation, and intense itching.
(4)Many more mites are free living, that is, not parasitic.
(5) Some are parasitic, such as the larvae of chigger, but nymph and adult are free living .
(6) Free-living house dust mites cause allergies in many people.
(7) Others can cause the destruction of stored grain and other products.
Harvestmen (daddy longlegs)
(1) Harvestmen, or daddy longlegs, look superficially like spiders but differ in many respects.
(2) They lack a waist separating the abdomen from the fused head and thorax, and their abdomen is segmented.
(3) They can ingest solid food as well as fluids.
(4) They do not produce silk and are non-poisonous.
(5) Harvestmen feed on insects and contribute to insect control, although they are less important in this respect than spiders.
(02) Class Crustacea - crabs
Crustaceans are a group of animals that have a hard exoskeleton, jointed legs, and a segmented body that is bilaterally symmetrical. They have two pairs of sensory antennae, one pair of mandibles (for chewing food), and two pairs of maxillae (to help the mandibles in positioning the food). Crustaceans are invertebrates (they lack a backbone) and arthropods (which also includes the insects).
Most crustaceans live in water, but some live on land. Crustaceans are the most numerous animals in the oceans, but some crustaceans live on fresh water. There are about 30,500 known species of crustaceans around the world.
Some Characteristics of Crustaceans:
A hard exoskeleton made of calcium - no internal skeleton.
(2)The head has two compound eyes, two pairs of antennae, and three pairs of mouthparts.
(3) A pair of green glands excrete wastes near the base of antennae.
(4) The abdominal segments have swimmerets (swimming legs)
(5) The sexes are separate. Eggs are attached to the swimmerets (swimming legs) of the female. The first pair is enlarged in the male (it is used to pass sperm to the female).
(6)The tail is fan-shaped, and ends in uropods and a telson.
(7) The circulatory system is open; there is no heart and the "blood" is pumped by vessels into sinuses, and does not flow in a closed loop.
(8) The nervous system consists of a primitive ventral nerve cord and ganglia system (similar to those of an earthworm).
Some crustaceans include:
Copepods are tiny crustaceans from fresh and salt water.
A crab is an animal with a crusty shell. There are marine and land species of crabs.
Freshwater crustaceans with four pairs of walking legs.
Hermit crabs are crabs that lack a hard shell; they use a discarded shell for protection.
Shrimp are small, bottom-dwelling crustaceans with a translucent exoskeleton.
(03) Class Merostoma- horseshoe crabs: