03 January 2013

Defends itself by squirting its own blood...

An armoured ground cricket, native of the Kalahari, 
prepares to defend itself by squirting its own blood through joints in its armour.

One of the photos in a Guardian gallery about David Attenborough's new television series on the wildlife of Africa.  I found confirmation in the cleverly-entitled "There will be blood..." article in the Journal of Zoology:
Armoured ground crickets Acanthoplus discoidalis (Bradyporidae) have an arsenal of defence mechanisms in response to attack. Males but not females can stridulate when attacked, while both sexes will bite and regurgitate upon provocation. They will also autohaemorrhage. Here we have quantified these responses, examining how individuals of both sexes respond to repeated simulated predatory attack from the side (grabbing the legs with forceps) or from above (grabbing the animal by the pronotum). We found different responses depending on the method of attack. When attack was directed from the side (at the legs) the crickets can bite their attacker and males stridulate intensely. About 62% of such attacks elicited an autohaemorrhage response, where the crickets squirt 13±22 mg of acrid-smelling haemolymph 43±63 mm from seams in the connective tissue between the trochanter and coxa of each leg and from under the pronotum. By contrast, animals attacked from above could not turn and bite their attacker, and stridulation was also reduced in males. About 86% of such attacks elicited an autohaemorrhage response with 19±19 mg of haemolymph projecting 10±30 mm from the body. Autohaemorrhaging is an effective form of chemical defence against bearded dragon lizards Pogona vitticeps (Agamidae) and Aca. discoidalis haemolymph applied to Gryllus bimaculatus nymphs (which have no such chemical defence) successfully saved them from predation by striped skinks Trachylepis punctatissima (Scincidae).
Word for the day: autohemmorhage.


  1. Makes me think of the wonderful horny toads (desert horned lizard) that I grew up with in West Texas. Now endangered, they were common in my youth. They are generally docile, but these guys can squirt blood from their eyes up to five feet if threatened.

    1. I'm embarrassed to have omitted that; my roommate in graduate school was a TCU alumnus...


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