Black House or Widow Spider

Brief:

The black house spider, Badumna insignis, is a common species of cribellate Australian spider, found throughout much of Australia and New Zealand. A closely related species, the grey house spider (Badumna longinquus), has a similar distribution. It is also known as the common black spider.

The black house spider is a dark, robust spider, the female growing up to 18mm, with a 30mm leg span. As with most spiders, the males are smaller (10mm), and have longer legs in relation to their body size. In both sexes the carapace and legs are dark brown to black, and the abdomen is charcoal grey with a dorsal pattern of light markings (sometimes indistinct) and a dense covering of fine, velvety hair.

Habits

The webs of black house spiders are a messy-looking construct of irregular sail-like shapes. There is a funnel-shaped, silken retreat, usually in the middle or corner of the web, where the spider spends most of its time waiting for prey. The female spider never leaves the web unless forced to. They are very territorial to their location, rarely changing the position of their webs and because of this old webs can be quite messy, often with small objects or dust stuck in them. At night the spider comes out to repair and add to the web, often just adding new silk over the old.

Males, when ready to mate, go in search of females. The male plucks the web of the female to attract her attention. Once the male has made sure that the female will be receptive, he will approach and inseminate her with his palps. They may then stay together for several days, and may mate again several times.

The female constructs several white silk egg sacs, which are secured within the web retreat. The female stays with the eggs until they hatch. The spiderlings then disperse. Occasionally the young spiders stay in the web of the mother for some time, catching the smaller prey that the larger spider would ignore.

Predators include the White-tailed spider, as well as parasitic wasps and flies.

Habitat

Black house spiders are widely distributed throughout Australia and New Zealand. In natural habitat, they are usually found on rough-barked trees, whereas inside buildings they are often found in corners, around windows and doorways, or other light sources that may attract prey insects.

Threats

Black house spiders are venomous, but are not considered dangerous. They are timid and bites from them are infrequent. The bite may be excruciatingly painful and cause local swelling. Symptoms such as nausea, vomiting, sweating and giddiness are occasionally recorded. In a few cases, skin lesions (arachnogenic necrosis) have developed after multiple bites.

Prevention

The best method to avoid black house spiders is through prevention, black house spiders like to inhabit seldom-disturbed areas and as a result regular cleaning and removal of potential hiding spots is a key prevention method. Weatherproofing and caulking exits will help limit the spiders entering the home.

Loose black house spiders should be sprayed with an aerosol pesticide, as attempting to hit or crush them will make the spiders aggressive. Powdering the web of a black house spider with a non-repellent insecticide dust is a further method of eradication.

Others

Photo  and information are provided by WR Gay Pest Control Pty Ltd  and Bayer.

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