What's That Bug? does not endorse extermination

yellow bettle? aquatic?
Location: Raymond, California
August 7, 2011 3:45 pm
I saw these two insects this morning in one of our creeks. They were both approximately the same length, but obviously different colors. The yellow one was firmly grasping the dark one – mating? Predation?
I am clueless on ids for both of them. Any ideas?
Signature: Megan Ralph

Giant Water Bug Nymphs compete for meal

Hi Megan,
We are confident that we have identified your insects as two immature individuals of a species of Giant Water Bug in the genus
Abedus, based on this image of Abedus herberti posted to BugGuide.  The yellow individual in your photos and the BugGuide image are newly molted nymphs in the teneral stage, meaning that their exoskeleton has not yet hardened and darkened.  Insects are especially vulnerable immediately after metamorphosis.  We believe the dark individual in your photos, also a nymph, is taking advantage of its weaker coeval by preying upon it.  Of course, your photos do not reveal the final outcome, and the teneral individual may have actually been the victor in this food chain drama.  BugGuide has a wealth of information on Abedus herberti, including this listed range:  “Arizona, Utah, New Mexico, USA; northern Mexico” and this listed habitat:  “Freshwater streams, especially in montane areas. They often inhabit intermittent streams, so they are isolated to individual rock pools (tinajas) during dry periods when streams do not exhibit overland flow.”  This interesting note of food may explain the cannibalistic behavior that your photo illustrates:  “All water bugs are predators. Abedus herberti eats other insects, small fish, small tadpoles, and will become cannibalistic when other food is scarce.”  One final bit of information from BugGuide indicates that this might actually be a closely related species from California, Abedus indentatus:  “Abedus is a difficult genus in which to identify species without a microscope for close examination. A. heberti is similar in appearance to most other Abedus species, but it is most similar to Abedus indentatus. A. indentatus is typically only found in California.”  BugGuide has a dearth of information on the California species.

Cannibalistic tendencies in Giant Water Bug nymphs

Thank you so much for your detailed and extremely informative reply.  That is the perfect description for the habitat where I saw them – a small stream that is beginning to dry up (rather late in the year actually – it was a wet spring).
Megan

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What's That Bug? does not endorse extermination
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