Araneus marmoreus encore
November 23, 2012 14 Comments
Here is the full-sized photo from which the crop shown in Super Crop Challenge #14 was taken. The small finger-like structure in the upper right of the photo—the object of the challenge—is the epigyne (or epigynum) of Araneus marmoreus (marbled orb weaver spider). Spiders have a rather unusual mating strategy—rather than possessing genitalia that couple for insemination, male spiders first form a packet of sperm (spermatophore) and transfer the packet to an enlarged segment (tarsus) at the end of their pedipalps. During mating, the male inserts the tarsus into the female genital opening, thereby effecting sperm transfer. The female genital opening and associated structures, located on the underside near the front of the abdomen, are called the epigyne and function to direct the male pedipalps during sperm transfer. The shape of the epigyne varies greatly and uniquely among species—probably serving as an isolating mechanism that prevents interspecific mating and also providing a good diagnostic character for species recognition among even very closely related species (similarly to the hardened male genitalia of many insect groups). An even closer view of the epigyne of A. marmoreus can be seen in this BugGuide photo.
This is actually the second time I’ve featured A. marmoreus in a quiz—the intricate pattern of the dorsal abdomen being the subject of Super Crop Challenge #2. Folks had an easier time identifying the critter in that challenge than this one, which I guess is not surprising since people tend to know animals more by their color patterns than the structures of their genitalic openings. As in that first challenge, I encountered this adult female during a hike along the Ozark Trail, this time in Washington County in east-central Missouri. Unlike before, however, I found this spider crawling on a fallen log in the dark forest floor rather than resting in her web. The colors of this species are diverse and spectacular—a recipe that makes them almost irresistible to insect macrophotographers. That this is true is demonstrated by the 360! photos of this species posted to BugGuide.
While my previous photos of this species were colorful, these simply glow due to the more orange coloration of this individual and its contrast with the darkened color of the moist wood. It’s a November color scheme if there ever was one—appropriate since I took them exactly one year ago today on November 23, 2011. She was a lot more cooperative than the first subject, and because of this and the stable substrate on which she was sitting I was able to get my favorite shot of all—the face portrait! Not quite as endearing as a jumping spider face (with its large, anthropomorphic median eyes), but striking nevertheless.
A word about the challenges—I’m not sure if the lack of response to this one is an indication of difficulty or further evidence of declining relevance of blogs as an interactive social medium. I can’t help but notice that blog commenting in general has dropped with the rise of more functionally interactive media such as Twitter and Google+. What do you think—was this challenge too hard, or has the concept of challenge posts lost its appeal?
Copyright © Ted C. MacRae 2012