Bug Spotlight!

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U.C. Riverside
Department of Entomology
 Amorphophallus paeoniifolia 
with Peltonotus nasutus 
(above) G. Ballmer Ó
P. nasutus male(L) female (R) 
(below) K. Osborne Ó
Peltonotus nasutus Arrow (Family Scarabaeidae, subfamily Dynastinae) by Dave Hawks                                                                

Scarab beetles do all sorts of varied and sometimes strange things, including feeding on dung, carrion, dried animal skin, fur and feathers, as well as more pleasant behaviors such as munching leaves or flowers, or sipping nectar.  The Peltonotus scarabs that Greg Ballmer collected during his recent trip to Laos are peculiar in terms of behavior, and also in having a very uncertain classification history until June of 2004.  These 2 cm long scarabs uniquely form large feeding and mating congregations of dozens of individuals inside and around the spathe of the large and unusual flowers of the aroid genera Amorphophallus and Epipremnum.  Amorphophallus famously includes the world’s largest flower, which also may be the world’s smelliest — reportedly producing a terrible odor similar to carrion.   Greg says that A. paeoniifolia, the flowers of which are over a foot in diameter, did not have a particularly bad odor.

Peltonotus is restricted to southeast Asia and consists of 19 described species, and was revised earlier this year by Mary Liz Jameson and Kaoru Wada.  Peltonotus has confused scarab taxonomists since its description in 1847 in that it possesses characteristics of both the subfamilies Rutelinae and Dynastinae.  Jameson and Wada placed it within the Dynastinae in the tribe Cyclocephalini, mostly because members of this tribe (which include the common tan-colored “May Beetles” of the genus Cyclocephala that frequent porch lights in late spring and summer) tend to have enlarged front tarsi in the males.  However, because I was able to sequence DNA from Greg’s fresh specimens, I now know that there is indeed very strong support for Peltonotus as a member of the Dynastinae, but it clearly is not a member of the tribe Cyclocephalini.  Instead, it is closest to another mostly southeast Asian genus, Parastasia, which, also based on very strong molecular evidence, presently is incorrectly classified as a member of the Rutelinae!  Some scarab beetles are very good at fooling taxonomists and their classification still obviously needs a lot of work.  And that’s why they’re so exciting!



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