3D Long-jawed Orbweaver Spiders & Ants


The spiders are longjawed Orbweaver spiders of family Tetragnathidae. They are Tetragnatha straminea (based upon my use of “Spiders of the Eastern United States” by Howell & Jenkins).

The prey is a female crane fly (complete except for the head–notice antenna also present).

The first ant appears to be trying every route it can to reach the prey item that it apparently smells. Later, one of the ants appears to be from a different colony as it runs off an ant already present.
The ants are apparently nothing to be messed with. The spiders are unable to reclaim the prey even when only one or two ants.
The fly is behaving like a kleptoparasite so it probably belongs to the family Chloropidae or Milichiidae.

There is some interesting research reported in 2012 on a closely related species: http://www.umdearbornreporter.com/2012/05/video-researching-the-feeding-habits-of-tetragnatha-elongata/. The authors found that these male spiders ceased web making upon sexual maturity and instead relies upon stealing prey from their female mates.

I assume the larger spider is the female because

  • She is larger,
  • Adds to the web on several short trips from the prey and
  • Is is the spider at the prey.

I assume the male is trying to partake of the prey because of the above mentioned research and because it approaches when the female at the prey and also approaches the prey when instead ants are at the prey.

Behavior I don’t understand:

  • Once the ant has first almost reached the female’s legs it runs as if it is on ice (its legs slipping). I don’t understand what caused this behavior unless it is excitement (but that seems too anthropomorphic).
  • Why does the male spider react with fast motions after approaching the ants. I cannot see any aggressive behavior on the spider or ants’ behavior. This is somewhat similar to the female rapidly climbing after its interaction with the first ant.

For Encyclopedia of Life entry for Long-jawed Orbweaver : Tetragnatha straminea.  For BugGuide.net entry: Tetragnatha straminea.

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