What's That Bug? does not endorse extermination

Ed. Note:  We have never heard of a situation where Spiderlings remain together after leaving the female’s protection, and we suspect the “conga line” you witnessed was of creatures other than Spiders.  The behavior you describe is more typical of social insects like ants or immature Hemipterans.  Are you able to provide an image?

Subject: spiderlings traveling in a “conga line”
Location: Chemuyíl Pueblo, México Yucatán
January 8, 2017 10:58 am
There are many unusual bugs in the jungle here, such as spiders and scorpions that carry their babies on their backs.
I was delighted to find your site – thanks!
Can you tell me about spiderlings traveling in a “conga line”, hundreds of them? Why?
Signature: Malcolm

Tarantula Spiderling “Conga Line”

Hi again Malcolm,
Thanks for sending an image.  Our initial response to you expressed our doubt that Spiderlings would travel the way you described.  We retract our supposition.  These do indeed look like Spiders.  We will attempt to find additional internet documentation that can explain it.

Tarantula Spiderling “Conga Line”

Tina Shaddock comments on Facebook
I believe these are plausibly Brachypelma vagans spiderlings and this article holds a bit of info about what is occurring in this photo.
https://www.researchgate.net/figure/262617778_fig1_Figure-1-A-column-of-about-200-B-vagans-spiderlings-observed-on-the-road-by-the

Ed. Note:  Here is a quote from the linked article:  “The spiderlings, which have a body length of about 2-3 mm, stay in the maternal burrow for several weeks. Little is known of this gregarious stage in this species, although spiderlings have been observed moving around the entrance of the maternal burrow, in where their mother is hunting in a sit-and-wait position. They often climb over each other but avoid contact with the mother. During daytime, the spiderlings were known to remain active and visible at the entrance of the burrow for up to one hour after the female had retreated. They were able to move easily through the web covering laid by the female over the burrow entrance (Shillington & McEwen 2006). Authors hypothesized that the silk network around the burrow provides an important chemotactic cue for orientation (Minch 1978) and juveniles probably remain in contact with this network at all times. After this gregarious period, the spiderlings disperse in the form of columns of about 100 siblings walking away from the mother’s burrow (Reichling 2000, 2003; Shillington & McEwen 2006). Shi- llington & McEwen (2006) observed that during the night of May 24 th 2003, spider- lings left the maternal burrow in three lines. Then at random intervals, one individual left the column and headed in a different direction, causing successive forks in the column. The maximum observed distance of dispersal was 9 m from the maternal burrow. Dispersal is observed in several spider species, including several species of mygalomorphae, all using silk for ballooning (Coyle 1983) or orientation (Jean- son et al. 2004). Previous reports on B. vagans mention that the spiderlings walk in line like ants (Reichling 2000), but no work has recorded the use of silk during dispersal. During their gregarious and dispersal phases the spiderlings do not show any aggressive behavior toward each other, as many spiders do (Gundermann et al. 1986; Jeanson et al. 2004).”

Thank you! That description sounds entirely likely – location, environment, and behavior. And attached is a photo of an adult found outside the house. Who would have guessed? I feel happy to understand the critters here in more depth.
For what it’s worth, I’d wager the spiderlings stay in line visually. From their non-colliding dynamics, and seeing individuals lose their place in line and orient from an inch away to rejoin.
Thanks again.
Malcolm

Tarantula

Hi Malcolm,
Thanks for sending an image of what we believe to be an adult male Tarantula.  We will be featuring your posting for a spell.

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What's That Bug? does not endorse extermination
Location: Chemuyil, Pueblo, Mexico
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2 Responses to Tarantula Spiderlings Exhibiting Unusual Behavior

  1. About other cases of “spiderlings remaining together after leaving the female’s protection”, we have two species of social spiders in Brazil, Anelosimus eximius (Theridiidae) and Parawixia bistriata (Araneidae). The second is only social while immature.

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