Thursday, May 8, 2014

A spider wedding in my lab tomorrow?

My technician, Greg, has been rearing a few black widow spiders in my lab for a few months. It all started with an egg sac donated from the Insect Zoo (thanks?). He has an interest in spiders and is the "go to" guy if you need a spider ID. Since I am not a huge fan of spiders, I don't take the time to learn how to identify them or get to know much about them. I will go 5 soybean rows out of the way to avoid an orb-weaving spider in August.

Why do we care about black widow spiders? The females are considered highly venomous, but human deaths are rare compared to the number of people envenomated. People bitten by a female black widow may have swelling, redness, muscle pain, nausea, headache, and cramping. The venom contains several toxins and in general sounds like a painful experience. The good news is they are predators, and eat insects and pretty much anything that gets caught in their web. There are a few species of black widow in the U.S. and they have a wide distribution in the southern states. It is possible for black widows to live in Iowa, but finding them here is more likely because they were accidentally introduced instead of established.

Today Greg let me know that a female and male black widow have reached adulthood. It took constant care to feed them (live) flies and clean their cages every week. The spiders are not large, with females about 1.5 inches long and 0.25 inches in diameter. Females are shiny black with a classic, red marking on the belly (ventral) side of the abdomen. 

Adult, female black widow, Latrodectus mactans. Photo by wiki.

I have to admit, males are not impressive (insert game show sound here) - smaller, and dull in color. The adult body is about 0.25 inch in diameter.

Adult, male black widow, Latrodectus mactans. Photo by Center for Invasive Species Research, University of California-Riverside. 

It was hard to take a good picture of the male and female spiders through the plastic rearing chambers in my lab. I didn't feel brave enough to take the lids off and get a close-up. 

Female black widow spider. Note all the dead flies on the bottom of the cage. She is an efficient predator and quickly kills her prey. 

Greg is going to put them together in the same cage tomorrow and see if they mate. Can you hear wedding bells? Male spiders are often wary of females because they are potential prey. So they spin a sperm web and put the packet on one of his palps (kinda like short legs used for bringing food to the mouth). The male will attempt to deposit the sperm in the female before becoming dinner!

I wonder what will happen at the spider wedding tomorrow? 
Male is currently in the left cage. 

If successfully mated, a female can produce several egg sacs that contain a few hundred eggs. There is a lot of cannibalism with spiderlings, and so not many actually survive very long. Males don't live very long after becoming an adult, but females could live a few years. Sounds like we have a pet spider in the lab...

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