The brown widow spider finds the warm shores of Karachi a hospitable habitat, but watch out for it as its venom is twice as potent as that of the black widow, making it at least 30 times more potent than rattlesnake venom, writes Syed Waqar Ahmed

 Karachi is crawling with activity! Don't let your thoughts stray to the office workers on I.I. Chundrigarh Road or the chaotic lanes of Empress Market.

There is another class of worker, one that goes about its work in measured silence. If you train your eyes away from the everyday mundane things around you and learn to look in the right places, chances are you will discover that your house is host to a thriving population of brown widow spiders.

The brown widow is a close relative of the black widow spider and shares a striking resemblance to it. The black widow has achieved great fame and notoriety, especially in the Americas and Australia where they enjoy an almost iconic status in popular culture. Alongside the tarantula, widow spiders have come to symbolise mans fascination and fear of the eight-legged.

While the much maligned tarantula is non-venomous and quite innocuous, widow spiders, in spite of their smaller size, seem deserving of the bad press they get. Not only is their bite venomous to humans, females in captivity have been known to bite and devour their mates after they have fulfilled their duty in procreation!

Further besmirching their reputation is their tendency to consider household goods, patio chairs shoes even shoes as comfy homes. Perhaps, it was with good measure that the widow family of spiders was given the scientific name, “Latrodectus”, which is Greek for 'biting in secret'.

While the brown widow's place of origin is unclear, it has been discovered in many warm and cosmopolitan locales. It is hardly surprising then, that it finds a hospitable habitat on the warm shores of Karachi.

According to Dr Jerome Rovner, one of the world's leading arachnologists, “So many species of spiders have been carried accidentally from their original lands to other countries; it is not surprising that the brown widow has taken up residence in India and Pakistan — well outside its original range.”

Growing up to an inch and a half in length, brown widows have an emblematic yellow-to-orange 'hourglass' design on their underbelly. As they suspend themselves upside down in their webs, the blazingly bright “hourglass” mark glares out as an unmistakable sign, as if sending a warning to keep away! The rest of its body is dressed in dull tones with dark stripes on its legs. These spiders weave a dense, low-lying cobweb and, being nocturnal creatures, emerge from it during the night. Their eggs are laid inside 'egg sacs', with each egg sac holding up to 250 eggs.

The egg sacs themselves are safely embroidered into the sinewy silk of the web, where the female watches and waits over them. The egg sacs possess the distinguishing feature of having conic protuberances on their surface. It is this unique 'spiky' appearance of the egg sac that can give away the identity of the brown widow to an otherwise untrained eye.

The brown widow is less aggressive than the black widow and injects less venom in its bite. Unlike the black widow, it does not aggressively defend its nest and is prone to skittering away or "playing dead" when threatened. However, in a departure from its rather timid reputation, arachnologists believe that its venom is twice as potent as black widow venom, making it at least 30 times more potent than rattlesnake venom!

Such an effective chemical weapon is an indispensable adaptation, allowing the spider to subdue prey many times its own weight or size, before it has had too much of an opportunity to run or fight back. However, unless you are the size of a brown widow's typical victim, say, a fly or a cockroach, you have little to fear from these tiny warriors.

They inject very little venom in their bite and are extremely hesitant to bite humans. It is for these reasons that they are considered the least offending of all widow spiders. A 1993 study carried out in South Africa concluded that although brown widows can bite humans, the bite is not clinically significant and feels little more than a bee sting.

While generally considered to be innocuous, it is still not desirable to have too many of these spiders crawling about your living space! Routine cleaning is the best way to clear out spiders and discourage their return. Cracks and crevices in doors and windows can be sealed or filled in to prevent easy re-entry.

The immediate vicinity of the house can be made less attractive to spiders by reducing clutter (e.g. garbage heaps and construction material) and moving it further away from the house. However, all attempts to 'clean out' these spiders from the immediate surroundings need to be measured and sensitive to ecological considerations. Indiscriminate steps such as the use of chemical fumigations outside the house can devastate the normal, ecological balance of the environment, while fumigation carried out inside is known to have insidious effects on human health.

One should also be on guard against a tendency to discount every other specie's right to existence in the pursuit of a human goal.

Spiders play an integral role in the web of life and destroying them unnecessarily is harmful to the environment, and in turn, to us

We should take into consideration that spiders spend their entire lifespan capturing and eating harmful insects such as flies, mosquitoes and locusts (about 2,000 in a year!). More so, most cases of humans getting bitten are caused when the spider becomes accidentally pinched or squeezed against the skin.

The venom and silk of the widow spiders is being investigated by scientists for possible applications in the biotechnology industry. Already, the venom has been observed to have a 'vasodilatory' effect on human blood vessels with potential applications in treating heart attack patients. Being a resident of most tropical seaports, the brown widow is here to stay. What remains is for us to recognise its presence and keep ourselves at a respectful distance from it.