I’m not exactly sure why I’m writing about spiders since I really don’t care for them, but I was intrigued when I read a recent story about a couple who bought a box of grapes at a grocery store on the border between Queensland and New South Wales, and brought a little something extra home.
The redback spider, a cousin of the black widow (hence its oft-used moniker, “the Australian black widow”), is one of the deadliest spiders in the world. Only the females are deadly, but they prefer to remain in their funnel-shaped webs. The bite of a male redback generally is only painful at the site of the bite. As deadly as the female redback can be, there hasn’t been a reported death from the species since 1979, thanks to an effective anti-venom introduced to Australia in 1956. Most redback spider bites occur during the summer months, when the arachnid is most active. The Australian Museum reports that approximately 250 serious bites requiring anti-venom treatment occur each year.
DID YOU KNOW? Dogs have a greater resistance to their venom, but cats, horses, Guinea pigs, and camels will most likely require anti-venom.
The body of an adult female redback is less than a half inch long. Her legs are slender, but the two front legs are longer than the other six. Her abdomen is round, deep black with a red longitudinal stripe on the upper surface and the familiar red hourglass on the underside. Juvenile females may also have white markings on the abdomen. They have two venom glands, one attached to each of its chelicerae (fangs).
The body of an adult male redback is significantly smaller than the female, measuring around a quarter of an inch long or a bit longer. He is light brown and has white markings on the upper side of his abdomen and a pale hourglass on the underside.
Redbacks prefer a drier habitat found in trash cans or sheds, outhouses, or under rocks, logs, tree hollows, and shrubs. They eat bigger spiders, like the trapdoor spider, crickets (the only reason I might like spiders), small lizards, and even an occasional snake.
The redback is nocturnal. Females stay concealed during the day, and then come out to spin their webs during the night. They usually remain in the same location for most of their adult life. Their webs are an irregular-looking tangle of fine but strong silk, and while the threads may seem random, they are strategically placed to support and entrap prey. The rear portion of the web forms a funnel-like retreat where she spends a lot of her time and where she leaves the egg sac.
Once alerted to some hapless creature’s frantic efforts to free itself from the web, the female redback approaches and sprays its dinner with a liquid glutinous silk to immobilize it. Once her meal is secure, she bites it multiple times on the head, body, and leg joints—liquefying its innards. She then wraps it in silk and takes it to her retreat at the rear of the web where she feeds on it over time.
Female redbacks live two to three years, while the males only live six to seven months. Neither can tolerate temperatures from below freezing to 104°F, but they need temperatures from 59°F to 77°F for a couple of months in order to breed.
Spiderlings live with their mom in her web for several days, then they catch a ride on the wind to establish a home of their own. They follow the light and climb out of the tunnel retreat to a high point like on rocks or logs. By extending their abdomens high into the air, they produce a droplet of silk which is drawn out into a long gossamer thread, and when long enough, the wind catches it and carries the spider away. This is known as ballooning or kiting. Soon the thread will catch on an object, and this is where, after falling to the ground, the spiderling will establish its own web.
BUT DID YOU KNOW? As spiderlings, they also eat each other.
Redbacks are widespread across Australia, but are also found in Southeast Asia, New Zealand, Japan, England, Belgium, the United Arab Emirates, and Iran.
Sources: wikipedia.org/wiki/Redback_spider; newsweek.com/extremely-deadly-spider-found-box-grapes-grocery-store