Spider bodies are divided into two parts (cephalothorax and abdomen) and have eight legs. In comparison, adult insects have a body consisting of three parts (head, thorax and abdomen) and six legs. Spiders should not be confused with Phalangium opilio (daddy- longlegs) who resemble them with their thin, sometimes long legs, but with single-part bodies. Only certain species of spiders (Pholcus phalangioides, Steatoda bipunctata, Larinioides patagiata, Salticus scenicus, etc.) are normally found in or on houses, but other species that normally live outdoors (raft spiders, argiopes, etc.) can sometimes be observed.
Spiders lay eggs that they often protect with a silk cocoon. When they hatch, the young sometimes engage in cannibalism. They resemble adults and undergo a few moults before reaching their maximum size (sometimes, after a year or more) depending on the species in question. Spiders can spend the winter in any stage of development. All spiders produce silk. It helps them protect their eggs, build shelters, and weave webs to trap or wrap up their prey. Some do not spin webs because they hunt their prey. Spiders also produce a safety thread when they move about; they attach it in places to break their fall when they let themselves go to escape a predator. In some species, the young are able to produce threads from the rear end of their body that allows them to be carried to new locations with the help of the wind.
Places where they can be found in the home
Spiders can spin their webs on the outside walls of houses, sometimes in large numbers. Indoors, they hide in places where there is less risk of being detected, such as attics, cellars, or in boxes. There is no need to be afraid of their webs since they are often seen only when they are no longer used and covered with dust. Besides, spiders that are potentially harmful to our health would not spin their webs in an obvious place on the ceiling or near windows. In the worst case, should you accidentally introduce one such spider in your home – for example by buying imported grapes at the grocery store – it would preferably take refuge in a dark corner.
Their presence in a house can indicate that they are finding live insects (or spiders or other invertebrates) to feed on. A careful inspection will help discover and reduce or eliminate insects. To do so successfully, you may first have to solve a moisture problem.
Reducing lighting at the same time will decrease the number of insects attracted to light and, consequently, the number of spiders that will come to feed on them. Note, however, that the spider Tegenaria domestica is able to fast for a very long time. On the other hand, lighting dark places where spiders hide is recommended in other regions.
Spiders manage to enter houses through an opening, or can be carried in along with an object. You should therefore plug and seal small openings in the house and inspect anything you bring in with a careful manner.
Above all, do not panic when you see spiders or their webs. Using pesticides to get rid of them is not recommended. Instead, inspect the interior and facades of the house to try to discover why they are concentrating in that place in particular. Webs can be removed and new ones will confirm that spiders are still around. Sticky traps can be useful in detecting spiders that do not spin webs. Objects and boxes lying around in the garage should be packed away neatly to avoid providing them with too many places to hide. Some suggest that no vegetation should be allowed to come in contact with the perimeter of the house. More often than not, you may have to solve a fly problem. A simple broom can be used to remove webs and provide support for the spider so you can move it outdoors. Some prefer to use a large jar turned upside down with a piece of cardboard slipped under it before turning it right side up, to trap the specimen. Your immediate environment will be healthier by avoiding the use of pesticides. In addition, by removing instead of killing these predators, that are highly useful in getting rid of many insects and providing food for animals, you will be preserving the natural balance. Furthermore, if you do decide to kill the spider without solving the problem of what is attracting it to this location in particular, it may quickly be replaced by one of its kind. Instead of using an insecticide outdoors, it is better to plug up and seal all cracks on the facade that can be used as shelter for spiders.
That said, the dislike shown toward spiders is widespread in our society. Spiders are second only to snakes when it comes to animals children like the least. Some people are also affected by arachnophobia (fear of spiders). The very low level of tolerance shown toward spiders is therefore easily understandable, as is the fact that many people see their vacuum cleaner as their most valuable ally. Sometimes, the assistance of a parasite management specialist will be greatly appreciated.
Spiders have chelicerae in the front of their body to allow them to inject venom to paralyze their prey and, sometimes, to defend themselves. They also inject digestive sugars to liquefy the contents of their prey. Spiders then feed by sucking out the liquid thus obtained. Others can reduce their prey to pieces beforehand. The rear of their body is fitted with spinnerets, and when a liquid is expelled, it is transformed into silk on contact with the air.
Spiders serve as bio-indicators, i.e., their diversity gives us an idea of the richness of the various natural environments. They are sometimes introduced as biological weapons to combat various insect problems but, in nature, they already play a major role in insect population control. A number of medical breakthroughs have been based on the use of venom or toxic substances. For example, trap-door spider venom can help treat cardiac arrhythmia.
As evidence of our fertile imagination with regard to the world of spiders, one European book mentions that some people wrongly associated an airborne swarm of young spiders with chemical warfare and UFO’s.
Many people would be surprised to learn that very few spiders are considered potentially dangerous to humans – a dozen or so species (often, tropical) – even though there are 37,776 known species on the planet. And even among those fearsome spiders, only one species (living in Australia) has a reputation for attacking without provocation. We should not think of spiders as creatures that can run and attack us. Very few can see more than a few inches away. NO SPIDER AMONG THE 620 KNOWN SPECIES IN QUEBEC CAN BE CONSIDERED DANGEROUS. Furthermore, the chilicerae of a good number of spiders are too weak to penetrate human skin. The bite of the spider Chiracanthium mildei – a small (7 mm), greenish, nocturnal spider found in houses – can result in swelling and necrosis (cell degeneration) of the skin in some people, and sometimes fever, headaches or nausea. Like the vast majority of spiders that could bite us, it prefers to avoid us, and usually only bites when trapped between clothing and the skin, or when provoked.
People who are allergic to the proteins in spider saliva can have significant reactions resulting from a bite. Some individuals are even bothered by inhaling some of their particles or hair found in the ambient air.
The large hairy spiders wrongly referred to as “tarantulas” are actually mygalomorphs (such as the trap-door spider). They are not found in nature in Quebec, but some have been observed in Ontario, close to our border. Dolomedes fimbriatus (2.6 cm raft spiders, but with long legs) that lives around our lakes and streams can resemble them and frighten people because, to some, trap-door spiders correspond to the image they have of a dangerous spider, but this is not the case. Instead, a better candidate would be a small, black, hairless, shiny spider – the black widow. Even the bite of one of these spiders, found in other Canadian provinces or to the South, will usually have more consequences for a baby, an elderly or sick person. People who live with them learn from childhood to look inside their shoes first before putting them on, not to leave sheets or clothing on the floor to prevent them from hiding there, and to inspect the seat of outdoor toilets. They can use a flashlight at night to locate them.
It is absolutely essential to be aware of a currently well-known phenomenon: A LARGE PROPORTION (80%) OF THE SYMPTOMS ATTRIBUTED TO SPIDER BITES ARE NOT CAUSED BY THEM AT ALL. Such symptoms should be associated instead with other invertebrates such as ticks or fleas, or other causes such as dermatitis or bedsores.