Friday, November 20, 2009

The Tactics of an Egg Tending Lynx

While stomping through a northwest Florida flatwoods community earlier this week, I took pause to admire a couple of swamp sunflowers (Helianthus angustifolius). The sunflowers’ brilliant yellow display glared brightly through the otherwise dark and rainy Tuesday afternoon and beckoned for a closer look. On turning-over one of the composite flower heads to better examine its calyx, I discovered a green lynx spider (Peucetia viridans). The spider was standing guard on top of its egg sac, which it had tethered securely to the optimistic sunflower’s underside with hard-wearing silk.

The green lynx spider is a member of the Oxyopidae Family and accordingly displays several traits characteristic for the group. In terms of identifying morphology, members of the group show a hexagon-like pattern of eye arrangement, and legs that bear large spines. Behaviorally, members of the Oxyopidae are aggressive daytime hunters which, as opposed to constructing webs, stalk their prey over the leaves and stems of the herbaceous groundcover. In regards to Peucetia viridans specifically, the spider’s body is translucent and exhibits a bright green coloration with red spots on the cephalothorax and black spots on its spiny legs.

Considering the presence of an egg sac and the sentinel-like bearing demonstrated by the spider appended to the sunflower, it was very likely a female. As a strategy, females of the species uncompromisingly guard their reproductive investment using a variety of tactics. These protective measures are necessitated by the low-to-the-ground habitat they share with a number of other voracious predators. Here in Florida, some of the most abundant and hostile species encountered by lynx spiders are fire ants (Solenopsis spp.)

The specific tactic used to defend an egg sac from fire ant onslaught is dependent on the intensity of the ant attack. Intensity is here a measure of ant quantity and the frequency of assault. Generally, female lynx spiders will utilize a mode of defensive escalation in which infrequent or isolated attacks from a single ant will be dealt with through deployment of a rapid and violent head-on confrontation. As the ant approaches the female, she’ll pounce forward and use her mass to knock the assailant from the plant, or, if failing to physically remove the ant, she’ll alternatively utilize her fangs to pierce the exoskeleton of her antagonist, ultimately slaying the provoker. The spider will almost always prevail during one-on-one combat with an ant, however if the ant attack is undertaken in number, evasion becomes the best option for the lynx.

If the incidences of attack become too frequent, or if the ants attack in larger quantities, mother Peucetia viridans will attempt to dissuade the egg-seeking aggressors by removing the prize for which they hunger – she’ll move the eggs out of reach. Once again depending on the seriousness and intensity of the ants’ offensive maneuvers, she’ll execute one of two evasive actions. One option is to cut all but a couple of the silk cables holding the egg sac in place, causing it drop from its anchor point and remain suspended in air; the second option to completely untie the sac and relocate to an entirely new host plant. The suspension method removes the eggs from hostility and forces any persistent attackers to travel down individual threads to continue pursuit – where they’ll undoubtedly meet an agitated mother face-to-face. Relocating the egg sac to a new host is a sure-fire way to end the current dispute however it is a risky option, because increased visibility during transport may leave both the mother and her eggs vulnerable to other hungry predators.

Eubanks, M. (2001). Estimates of the Direct and Indirect Effects of Red Imported Fire Ants on Biological Control in Field Crops Biological Control, 21 (1), 35-43 DOI: 10.1006/bcon.2001.0923

Linda S. Fink (1987). Green Lynx Spider Egg Sacs: Sources of Mortality and the Function of Female Guarding (Araneae, Oxyopidae Journal of Arachnology, 15 (2), 231-239


  1. Interesting stuff. I wonder if the presence of non-native fire ants will have any long-term impact on lynx spider populations.

  2. Ted,

    I’d wager that although the fire ants are impacting lynx populations now, this impact will lessen with time. Currently fire ants are spreading like (dare I say it) fire. As they continue to spread in what is (for them) a relatively open ecosystem, their numbers may reach a threshold that gives advantage to increased territoriality; this may push the ants towards a better balance with our local fauna.

    M. J. B. Krieger (2005). Molecular Evolutionary Analyses of the Odorant-Binding Protein Gene Gp-9 in Fire Ants and Other Solenopsis Species Molecular Biology and Evolution, 22 (10), 2090-2103 DOI: 10.1093/molbev/msi203

    Incidentally, I’ve just discovered your blog site – it’s great. It’s been added to my blogroll. Thanks for the comment.

  3. Hi Johnny,
    I'm here visiting from CotS, and see that you have come across much the same scene as I have. The beautiful Green Lynx spider and her egg sac. I love the behavior study - I had come across the Linda Fink paper as well. Fascinating.

    I really like that second photo - great angle.