Spiders belong to the phylum Arthropoda, along with insects and crustaceans. The order of spiders, Araneae—together with scorpions, harvestmen, and the large order of mites and ticks—make up the class of Arachnida. Spiders differ from other arachnids in having the body divided into cephalothorax and abdomen. About 43,000 spiders are known, but many have yet to be discovered and described.
Spiders are found in all terrestrial habitats on all continents. Some are even found on or in fresh water. They range from less than 1.0 mm long to tropical tarantula size with leg spread to 25 cm (10 inches). Spiders are more abundant in tropics than in cold countries. They feed on living prey, usually insects. Many spiders hunt their prey, some build burrows with trap doors, others sit camouflaged on plants, and many build webs to snare insects. Hunting spiders may have good eyesight, while web spiders have poor vision but an excellent sense of touch. Fine setae (or hairs) on their legs are sense organs for vibrations. Most spiders are solitary, but in warmer climates some spiders are social, many in a web. Enemies of spiders include some wasps, spiders and birds.
The body of a spider consists of an anterior cephalothorax and a posterior abdomen joined by a pedicel. The cephalothorax contains the brain, stomach, and usually venom glands. The digestive tube, blood vessel, nerve cord, and some muscles pass through the pedicel. The abdomen contains the heart, digestive and reproductive systems, lungs or trachea, tubes for air, and also silk glands. It is segmented in only one small group of spiders in southeast Asia. At the posterior end it bears usually six spinnerets with spigots, each with a different kind of silk. There are usually eight simple eyes on the cephalothorax, sometimes fewer. Attached to the cephalothorax anteriorly is pair of short jaws, each with a fang containing a venom duct; four pairs of legs; and between jaws and legs, a pair of short, leg-like palps.
The palps of males are enlarged and modified to pick up sperm previously deposited on a silk strand from openings on the venter of the abdomen. The palps then transfer the sperm into the opening of the female genital area, which in most spiders is the sclerotized epigynum. The epigynum and male palpi are important to the taxonomist to separate species. The female deposits her eggs wrapped in a waterproof silk sack: only a few eggs in spiders that guard the eggsac up to hundreds in others. Young spiderlings hatch and become mature after 4 to 12 molts. A wolf spider mother carries her egg sac with her and newly hatched spider lings ride on her abdomen. Most adult spiders live 1–2 years, but female tarantulas may live 20 years.
Unlike other silk-producing animals, spiders use silk in many ways. Most use it to wrap their eggs and some build nursery webs. Young spiders of some groups balloon: they climb up on vegetation, let go of some silk, and float off with the wind. Silk is used by some spiders to line their burrows and sometimes to make trap doors. Spider safety depends on a dragline of silk: if an enemy approach, the spider can drop quickly. Most important, silk is used for webs to trap insects. A web is built, and some silk lines are coated with sticky silk. The spider may sit at the edge in a silken retreat, from which it responds to vibrations. Bolas spiders attract insects with odor and throw a sticky silk ball at approaching prey. In addition, silk is used to wrap and store prey for future meals.
Widow spiders (Latrodectus), which occur in most parts of the world except for central and northern Eurasia, are venomous. The bite is painful but rarely fatal. In the Americas, the bite of the brown recluse (Loxosceles) spiders causes dead tissue in the region of the bite. The bite of Atrax, a venomous funnel weaver found in southern and eastern Australia, may be fatal. Large tarantulas of the United States are not venomous but may brush off their irritating setae.
How to control house spiders?
Spiders are the exclusive household insects, which are one of the most-feared of all pests in the home that people want to exterminate. There are more fears and phobias about Spiders among people, than any other pest, and understandably so. If one is bitten by the poisonous spider – a black widow or a brown recluse –the person will have a bad reaction to the venom, one can end up in the hospital. And there may even be deaths.
The effective Spider control measures in domestic premises are-
- Spider control cannot be done to perfection. Chemicals are not very effective against spiders, nor do the spiders readily pick up pesticides. So just spraying pesticides is not a great defence against spiders. With their long legs, Spiders can keep their bellies well above the ground, so sprayed insecticide residue on a surface will only touch their feet. But they don’t have a circulatory system that will carry the insecticide from the bottoms of their feet to the organs in their bodies that would cause them to die.
- It is necessary to make contact with the insect through a direct spray, a newspaper, a shoe, or whatever is your weapon of choice. Spiders are not actually insects. True insects use their mouths to groom themselves, so they end up eating insecticide that gets on their feet, legs, and bodies. But spiders don’t routinely use their mouthparts to clean themselves. They clean their leg if there is a large particle stuck to it, but it’s not a habit that will guarantee pesticide will kill them. In addition, most spiders spend their entire lives sitting in webs,
The best way to control running and jumping spiders at home is to control their food sources around the house. Spiders eat other insects, so reducing the other insects around home will reduce their food sources, and spiders will be less interested in hanging around. Most spiders like to hang out near light sources, which helps them capture flying insects that are attracted to light. A web-spinning spider worth his salt will let his meals come to him; hunting spiders are more athletic—they really do run down their prey. A subcategory of hunting spiders is jumping spiders. They have more of a pouncing behaviour to capture their prey. The spiders with short, stubby legs are almost all of the jumping variety. The spiders with long – but not delicate – legs are the running spiders.
To get rid of spiders, get rid of all other bugs. Crack and crevice treatment with insecticides provide some control, but one can also use glue boards or sticky traps. These are non-pesticide capture mechanisms. Some can be folded into a box shape so that unintended items won’t get stuck to them. There are really no attractants in most of these glue traps. The sticky trap, or glue trap, just captures spiders – if they walk through the trap, they die. But one can’t cover much surface area with a trap, so one has to place them where the spiders are most likely to come to them. The most effective places to put glue traps are in dark, quiet areas. A closet is a good example, or between a bed and a wall, or by any piece of furniture – these are all common spider travel areas.