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COMMON SPIDERS: IDENTIFICATION AND TREATMENTS

Jim Westhead from Bayer offers pest managers new and old a recap of our most common pest spider species and recommendations for appropriate treatments. 

Many experienced pest managers are regularly treating spiders, both residentially and commercially. The types of warranties they give their customers differ widely, from giving no warranty at all, to a six-month or even 12-month guarantee on their work. The success in treatment will depend on correctly identify the nature of the spider problem and applying appropriate products.

This article aims to give some less experienced pest managers information on the most common spiders, as well as some tips on how to treat them, which can also serve as a refresher for those with more experience.

Understanding your customers

First and foremost, the most important thing is to understand your customers’ needs. Some customers simply want the pest manager to ‘nuke’ the property and kill every living spider, but others are happy for the spiders to live outside (in gardens, trees, fences, etc.) as long as they don’t pose a threat to them or their families.

So the first step is to ascertain exactly what the customer expects; then plan the job and do a full inspection to identify the spiders on site, determine the extent of the infestation and decide what treatment is required. This might be a dust, repellent liquid, non-repellent liquid, or good old physical removal.

Knowing your pests

It is very important for professional pest managers to understand the habits of each species of commonly encountered spider. There are nine common spiders around homes in Australia: mouse spiders, huntsman, white-tailed spiders, wolf spiders, redbacks, black house spiders, daddy long legs, orb weaver spiders and funnel webs. They can be generally divided into two groups: web-spinning spiders and non-web-spinning spiders.

Non-web-spinning spiders

The mouse spider (Missulena spp.) lives in tunnels in the ground but has no trapdoor at the tunnel entrance. It feeds on variety of ground-dwelling invertebrates. Its spiderlings disperse on gossamer.

Females are around 25mm long and dark brown/black in colour while the males are around 15mm long with a distinctive glossy, black cephalothorax and legs. There are different coloured mouse spiders including the redheaded mouse spider (the male has the red colouration). Most recorded bites have not produced serious reactions as the mouse spider releases a smaller amount of venom than other dangerous species. Not to be confused with the funnel web, the mouse spider is a more chunky spider with bigger jaws, there is a step step down from the front to back of the head and eight small eyes are spread across the front of the head (in the funnel web they are grouped together at the front of the head).

Mouse spider
Mouse spiders are very ‘chunky’ spiders with small spinnerets

The fearsome-looking huntsman (Sparassidae spp.) is one of most common spiders found in homes, which appears at night as it hunts on walls and ceilings. It is capable of rapid movement, often sideways. Females are around 40mm long, brown/grey with several pairs of dark spots on the upper side of the abdomen. Males look similar, only smaller at around 25mm long. A non-aggressive spider, huntsman bites are rare and cause redness and swelling, unless a badge huntsman bite, which causes a more severe reaction.

If a customer reports sighting a spider in the bedroom, chances are it’s a white-tailed spider (Lampona cylindrata). These wandering spiders are active at night, and by day can usually be found in piles of clothing on the floor, an environment that replicates their natural habitat of the underside of tree bark and beneath rocks. They feed on other spiders, particularly black house spiders. Both males and females are dark grey with a white patch at the tip of the abdomen, with females being around 20mm long and males around 12mm long. Bites are painful but not life-threatening.

The unusual-looking wolf spider (Lycosa spp.) is noted for its 4:2:2 eye formation (eight eyes in three rows). Other features to avoid confusion with a huntsman – the wolf spider will normally be found on the ground and hold itself above the surface with its legs spread evenly around the body. It is commonly found in gardens, where it makes holes in ground, covered by leaf litter. It moves very rapidly and is non-aggressive, although bites are painful. Females are around 20mm while males are around 10mm.

Close up of wolf spider eyes
The 4:2:2 eye arrangement of the wolf spiders (third row of eyes on top of head just visible)

Recommended control methods

David Gay, manager of W.R. Gay Pest Control in Melbourne, is a past president of AEPMA and currently chairman of FAOMPA. With over 40 years in pest management, Mr Gay is experienced in spider control. He advocates the use of dust treatments.

“Dusting of roof voids is particularly effective in dealing with non-webbing spiders like the white-tailed spider and huntsman,” Mr Gay explained. “These spiders can enter buildings from trees and overhanging branches, so dusting is a good control method.

“It also ensures a safe treatment in voids, and eliminates the possibility of electric shock that comes from misting, or other treatments. There is often a perception from the customer that these voids are where the spiders breed, so treatment of them helps with customer satisfaction.”

Web-spinning spiders

Perhaps the most notorious spider of all, the Sydney funnel web (Atrax robustus) is a highly venomous spider than is generally found within a 50km radius of Sydney CBD. Its bite can be deadly, as it contains a neurotoxin that attacks the nervous system. Since the introduction of antivenin, no fatalities have been recorded. They are dark brown/black in colour and are found in areas that are dark, moist and cool, such as under rocks in gardens. There 40 species of funnel web spider in Australia, but only six have been reported to cause severe bites.

sydney funnel web showing long spinnerets
In contrast to the mouse spiders, the Sydney funnel web has long spinnerets

Usually found under logs, bark and rocks, the redback spider (Latrodectus hasselti) is more commonly encountered in low-lying areas in sheltered environments, such as around the wall-floor junctions of sheds and garages, outdoor toilets and rubbish bins. Its webs are tough and sticky, usually tangled with no discernible pattern or defined structure.

It is only the female that displays the red stripe on its upper side. It is around 10mm long, whereas the male is much smaller at around 4mm. Redbacks are highly venomous and treatment with antivenin is often required.

Black house spiders (Badumna insignis) usually take up residence in buildings in the corners of window frames, around doors, and pergolas, weaving lacy sheet webs with one or two funnel-shaped entrances leading to a tubular retreat. They are solid-looking, with a blunt square-ended cephalothorax. Females are around 20mm with shiny black legs and cephalothorax, with males paler in colour and half the size. Bites cause general symptoms of nausea and localised pain.

Black house spider in web
Black house spider, Badumna insignis

A delicate spider with long slender legs, the daddy long legs (Pholcidae or Pholcus phalangioides) is commonly found indoors in dark areas, such as behind doors, in disused rooms, around furniture and in architrave areas. Outdoors, it is found in sheltered areas such as in sheds and under eaves. Its tangled webs are usually around 30cm in diameter and tend to accumulate dust, the type normally seen in the corners of buildings. Both males and females are around 7-8mm long and a pale brown colour. Harvestmen (which are not spiders) are sometimes mistaken for daddy long legs but harvestmen lack median restriction in the body and are rarely found indoors.

Orb weaver spiders create large, impressive webs that can can startle anyone who walks outside at night without a torch! Although many species aren’t especially large, they are considered a pest species as many customers are unnerved by their obvious presence on a property (although others love the symmetry of their webs).

Golden orb weaver spider in web
Golden orb weavers are amongst the larger of the orb weaver spiders

Recommended control methods

Mr Gay believes a slightly different approach is required when dealing with web-spinning spiders.

“In selecting treatments, it is important to understand the spider’s habitat and habits i.e. think like a spider,” he advises. “Crack and crevice treatments are far more important than band spraying of surfaces – spiders will often retreat to their web or hiding place for many reasons.

“Therefore it is important to treat obvious cracks and crevices, under eaves, particularly in cracks where the eaves abut the property, vents, fans, weep holes, clothes line holes and cracks. Where possible it is good practice to spray the webs – spiders will consume much of the existing web to spin a new web so even small amounts of chemical on the web will be effective.”

Choice of product

There are some general considerations pest managers must take into account regarding spider control products. These include: speed of knockdown (customer perception of immediate control); residual activity (callbacks); the type of surface to be sprayed; and the most suitable formulation. The advantages of pyrethroids are that they are fast acting and have flushing activity. (It is worth noting that owing
to low reproduction rates, spiders do not present a great potential for insecticide resistance development).

Bayer has a number of products that are effective against spiders and the latest product to hit the market is exceptionally effective. Suspend Flexx Insecticide has a unique formulation with deltamethrin crystals on the outside of droplets, making it far more accessible to spiders and other insect pests. The flexible label allows for four different application rates, enabling professionals to select the rate that will provide the desired residual activity. For example, for commercial jobs that are treated monthly, the lowest rate can be used, making it an extremely cost-effective treatment or product.

Suspend Flexx is a sound choice for targeting web- spinning spiders, applied as a spray to cracks and crevices. For non-web-spinning spiders, one of Bayer’s insecticidal dust products would be highly effective.

More information on spider identification.

Jim Westhead, Territory Sales Manager, Bayer