Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [60]
This rather convoluted process means that males can potentially waste a considerable amount of the females' time by persistently grabbing them in midair and chasing them around a pond or stream. Given that the females live only a few days or weeks in most species, and that it's important to find the best place and time to lay eggs, such harassment is more than merely annoying—it can compromise the female's ability to reproduce. The malelike morph of the females in the blue-tailed damselfly and several other species is thought to have evolved to allow the masquerading females to avoid some of the pestering, because males initially at least mistake them for other males and are less likely to bother them. This in turn means that selection will act on the males to make their acceptance rules for whom to court and who to shun a bit more flexible, so as not to miss out on any mating opportunities.
Van Gossum suspects that having this relatively open-minded response to all members of the same species, regardless of sex, means that a certain proportion of male-male pairs is inevitable, even though they obviously cannot increase the reproductive success of the males involved. The idea is that it's better to have a coarse decision threshold and risk accepting some mistakes than to be more discerning and risk missing some actual females. It's a bit like testing for certain cancers, where doctors would rather put some people through unnecessary biopsies and anxiety for a false positive than risk missing some actual signs of disease. In evolution, as in medicine, where to set the bar is not always clear.
Boys Will Be Girls Will Be Boys, Naturally
PEOPLE sometimes conclude from this kind of work that the damselflies, or Gillespie's spiders, or any of the other insects and their kin observed in homosexual pairings are making a mistake, and therefore human homosexuals are likewise in error, some kind of evolutionary fluke. Interestingly, a National Geographic story on Van Gossum's study suggested, "Such flexibility may also lead to genuinely homosexual damselflies." This implies, I suppose, that the damselflies in the Belgian experiments were somehow not really gay, although it's hard to know what the litmus test might be.
Instead, I think it makes more sense to see the flexibility in mating behavior, same-sex courtship and all, as part of the animals' natural repertoire. We cluck disapprovingly over the males' supposed errors, but that represents our misunderstanding of how evolution works. François Jacob famously said that nature is a tinkerer and not an engineer. What he meant was that natural selection doesn't produce perfection; it produces traits that are good enough. We often think of this in connection with our bodies, so that we have spines that are not really adapted to walking upright or immune systems that sometimes overreact to give us allergies to harmless substances, but the slop is part of every system, including behavior.
The chrysanthemum longicorn beetle (Phytoecia rufiventris) is a lovely insect with a ruby red spot on its back and a rust-colored abdomen. It is a pest of chrysanthemums, as the name suggests, and a single female can kill as many as seventy plants by laying her eggs in the stems, which makes understanding the beetles' biology of interest to horticulturalists. Unlike many insects, the chrysanthemum beetle lacks sex pheromones, those come-hither odors often employed as long-distance mate attractants and sex identifiers. The sexes find each other in the first place because both males and females are attracted to plants of a certain height. Qiao Wang at Massey University in New Zealand and his coworkers discovered that the male beetles reacted similarly to males and females when they first encountered them on a plant stem by attempting to copulate. After the male mounts, he engages