Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [59]
Admittedly, The Entomologist's Record is not the most prestigious or widely cited of journals and contains quite a few other anthropomorphic articles, such as the poignantly titled, "Do Copper Underwings (Amphipyra spp.) Crawl Away in Order to Die in Peace?" Nevertheless, same-sex behavior in animals, whether sheep or butterflies, seems to bring out this kind of histrionic reaction in those who observe it. And Bagemihl points out that we are probably seeing only the tip of the homosexual iceberg, since many more researchers may be seeing similar behavior in their study organisms but ignoring it or dismissing it as a meaningless aberration.
Because insects do not invite the same identification or anthropomorphism as mammals and birds, though, we can at least hope to use them as testing grounds for our ideas without automatically falling back on our biases. Most modern scientists would dismiss the idea that moral standards exist at all in butterflies, much less that same-sex behavior is a sign of them. What kinds of homosexual behavior do we see in insects and other invertebrates?
For example, the males and females of a small spider that biologist Rosemary Gillespie studied in Hawaii do not exhibit any elaborate courtship behavior before mating. Instead, they simply leap at each other, fangs outstretched. If such abrupt amorousness is acceptable to both parties, the fangs become locked together (giving new meaning to the phrase "hooking up"), and the female curls her abdomen around so that the male can insert his sperm-bearing organ into her reproductive opening. A captive pair of males that Gillespie had collected a few weeks earlier exhibited much the same behavior in their container, remaining coupled for 17 minutes. Similar same-sex pairings, usually between males, have been seen in captive and wild beetles, locusts, wasps, and a kind of fly that lives near streams and lays eggs in water lilies.
In the blue-tailed damselfly, females come in three colors, one of which resembles that of males. Hans Van Gossum and his colleagues at the University of Antwerp in Belgium kept male damselflies either with other males or in mixed-sex groups and then allowed the males to choose between a female or another male in a small cage. Males that had experienced the damselfly equivalent of a British boarding school were more likely to then seek out another male and form a pair with him, while the males from the coed environment were more likely to pair up with a female.
To interpret this puzzling result, we need to know some details about the sex lives of this insect group. Mating in damselflies and dragonflies is both distinctive and complex, and because the insects are aerial, one can often see mated pairs flying over the surface of a stream. A male damselfly or dragonfly, unlike other insects (and most other animals, for that matter), actually has two sets of genitalia, one at the tip of his abdomen and the other closer to the center of his body, at the underside of the second abdomen segment. Before mating, the male transfers his sperm from the tip to the more central location. Then, once a male sees a female he intends to mate with, he flies up and grasps her behind the head with his rear appendages in what is called a tandem position. The pair may fly together like this for several minutes or even longer. Eventually, if the female does not reject the male, they land on a plant or some other object and form a wheel: the female bends her abdomen tip to reach the male's secondary genitalia so that he can transport his sperm into her reproductive tract. (I've always thought the wheel looks a lot like a heart, and often show images of paired damselflies to my class on Valentine's