What's That Bug? does not endorse extermination

Spider Trapping a Baby Black Widow
Location: Southern California
November 4, 2010 1:10 pm
We found this spider in our backyard on the patio trapping a baby black widow. We are thinking it is either a male black widow or a brown widow, but are uncertain. We live in Southern California in the Murrieta/Temecula area. We would love to find out what it is. Thanks!
Signature: Courtney

Black Widow Cannibalism

Hi Courtney,
We are intrigued with your photos of Black Widow cannibalism.  The predator in this photo is an immature female Black Widow that will eventually lose that striped pattern and become a glossy black spider, and the prey is exhibiting the telltale red hourglass of a Black Widow as well.

Black Widow Cannibalism

Thank you so much.  Is Black Widow cannibalism common?  Do all females change like this?  Would it have started out all black like the baby here? I understand if you can’t answer all my questions, but I thought I’d try.
Thanks,
Courtney

Hi Courtney,
We were going to paste the third of your photos into this response so we could better determine the identity of the victim.  We have never seen data on the frequency of Black Widow cannibalism, but the name and alleged reason may be an indication that there is fact in the lore.  With that said, this may be a virgin adolescent female who is still wearing her prepubescent markings.  That may be a suitor that sacrificed his life for the perpetuation of the species.  Black Widows may be able to mate as adolescents and then storing the spermatozoa until it is needed.  Adult females are glossy black and we have not seen documentation of mature females marked otherwise.

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What's That Bug? does not endorse extermination

One Response to Black Widow Cannibalism and potential undocumented Bug Love

  1. Remirez says:

    According to Martin Filmer’s book on Southern African Spiders (I realize Latrodectus mactans is a North American species…), the males of family Theridiidae possess stridulatory organs that produce a frequency that makes the female receptive to his approach. She will then allow him to insert his palps into her epigynum to deposit his sperm. If he then does not get out of the way fast enough, his charm will wear off quickly and she will prey on him. If he does get away fast enough, he’ll live to see another day.
    So, although there is little evidence to show that this cannibalism occurs at every mating, it is a common enough occurrence to earn Latrodectus species the title “widow”.

    Also (as is stated above), unlike Mygalomorphs (mostly burrowing spiders), most Araneomorphs can retain sperm for days or months, even after ecdysing (molting) several times until maturity is reached.

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