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Shall we... dance?
Looking out my study window at what by August has become a sea of lantana and blue mistflower, I wonder why any butterfly remains active at 105 degrees. Naturally a butterfly can get too hot and must regulate its body temp by retiring to the shade. While some nectaring is taking place on the sun-soaked plants, I just noticed a more intimate activity among the large, shaded leaves of a sunflower goldeneye (V.dentata). There, a male and female are joined and look all the more beautiful for being together. But, as important as this joining is, it understates the complexity of butterfly reproduction.
Each year when you see the first adult members of a butterfly species, chances are that you're looking at males. Males tend to emerge from their chrysalides many days before the females of their species. Nature appears to have at least several reasons for this. One is to allow a male to establish a good territory, one having one or more host plants nearby that its species will use. Gulf fritillary males will settle into an area where passions vines are growing. And I recall the Tiger Swallowtail activity behind the Hardwicke Interpretive Center last spring, as the Tigers spiraled among the Texas ash. Also, hill-topping is a common activity for some species such as Swallowtails, and, in this instance, a male Tiger would occasionally light on an ash tree and sit with its wings spread, waiting for the right companion to come along. I've seen a Red-Spotted Purple do the same thing, patiently waiting on a hill up at LBJ Grasslands. We call this approach to finding a female "perching." Having staked out a territory, males will aggressively fly out to examine another butterfly, to determine if it's one of their species and if it's a male or a female. Males are naturally challenged, and research has shown that intruders almost always leave. Of course, some species' males more actively fly and search for a female, an approach we call "patrolling."
Another reason for the early emergence of males is that they need some time physically to prepare for females. Many engage in puddling, drinking from moist areas of the ground in order to obtain various minerals necessary for the production of pheromones. On other occasions the males are obtaining chemicals useful for developing their sperm packets. Sometimes these chemicals are derived from the nectar of particular plants. We often watch amazed at the huge number of Monarch and Queen butterflies that nectar on Eupatorium greggii. Phil Schappert suggests that they obtain alkaloids from the dried flower heads. Other researchers have suggested that males of these species are obtaining from the nectar the chemical lycopsamine, an alkaloid vital to their production of pheromones (biochemist Jerrold Meinwald recounts the research that led to this discovery in a fascinating article, "Sex, Violence and Drugs in the Lives of Insects: A Chemist's View." -- See web site below**). Females chemically analyze the pheromone and choose their mate based on the information received. As Dr. Meinwald notes, it's not necessarily the largest, brightest, or boldest male chosen, but sometimes the one with the best drugs.
Evidently the alkaloids and other minerals taken in by males serve another function in the great mating dance. As Phil Schappert reminds us, caterpillars don't take in significant amounts of salts and minerals on their foliage diet. Thus, it's necessary for the adult male butterfly to consume these ingredients. And just as the males of some animal species offer "nuptial gifts" to the female as part of their courtship, so too do butterflies. As Dr. Schappert observes, "Male butterflies... give females a 'gift' during copulation - a package of nutrients, salts and sperm called a 'spermatophore'. These are not small gifts - a spermatophore can weigh up to one-half as much as a male butterfly - and females depend on it to provision their eggs." (See A World for Butterflies in "Booklist" on this page.) Thus, the advance nectaring and puddling of the male not only allow him to attract a female but also enable him to pass on to the female and their offspring vital nutrients - fats, salts, nitrogen and chemical compounds" vital to reproduction. The male's gift also frees up the female to concentrate on flying and locating host plants.
Courtship and mating among butterflies seem almost as varied as the species themselves. It's usually believed that initial recognition among species is accomplished by visual examination of the color and pattern of the wings. (This, however, doesn't prevent an occasional attempted mating between males.) Research by the Smithsonian Institute published this summer suggests that in tropical environments various species depend on the reflection of polarized light in specific patterns from the wing scales of their own females. Regardless, the approach of the male to the female varies. Fluttering of the wings; attempting to force the female to the ground; releasing pheromones by brushing against or by spraying; landing face-to-face and ritualistically sizing up one another - all these mannerisms and behaviors comprise a complex palette in the art of butterfly courtship. When pheromones, etiquette, and other visual signs are satisfactory, the couple will proceed with mating. Usually the male lands beside her and twists his abdomen around to grasp hers. Once joined, the male and female are facing in the opposite direction. And mating may last anywhere from less than an hour to over twenty-four hours.
Occasionally matters become more complicated. You'd be amazed, for example, at the sexual aggressiveness of Gulf Fritillary males. Earlier this summer I noticed what appeared to be a cluster of Gulf Frits on a plant's foliage. Investigating, I found a couple joined together but surrounded by two or three other males who continued to try to separate the couple (other species such as Hairstreaks do this as well). Annoyed, I intervened, scaring the other males away so that our couple might finish their dance. (Equally aggressive Gulf Fritillary males - clearly lacking any sense of romance - are notorious for beginning to mate with females who have only begun to emerge from the chrysalis, a behavior described by some lepidopterists as the insect equivalent of rape.) If a joined couple is disturbed, the female (the larger of the two in most species) flies with her companion in tow to a nearby and hopefully safer spot. Watching that brief flight, I'm reminded of the increased vulnerability of both butterflies at this time and, if I may project a little, I suspect that both can hardly wait to be separated. In fact, once the female has received the male's package, she has no more need of him. In most species she will, however, mate again in order to obtain even more nutrients from another male's "gift." Incidentally, only the sperm of the last male to mate with her is utilized to fertilize her eggs.
A female who has mated may sometimes choose not to mate again when approached by a male. Or a particular male may not appear desirable as a mate. In those instances the female utilizes a basic strategy. Commonly, she will twist her abdomen upwards between her wings so that it is inaccessible to the male. As you might suspect, some males' persistence is unrelenting, though. The Texas Crescents in my yard behave in this way. The male will approach a female; she will avert her abdomen; he will fly in a tight circle, around and around, an inch or so above her, and alight, only to be rejected. He will continue this process over and over again. The males of some species are unwilling to chance that their female might mate again. Once mating is complete, the male deposits a "sphragis," a film or "mating plug" over the tip of the female's abdomen. This covering is tough and prevents the female from mating until it is abraded or falls off. An alternative is to coat parts of the female with a scent that is repugnant to other males, a scent that may last long enough so that some of the fertilized eggs are oviposited before another male can mate with her. Some females will mate only once, while others, more than once. It appears that the males of virtually all species try to mate many times. And after all, in the case of butterflies, it's not about commitment. It's about passing on genes.
Here are the most useful guides I know of to help you plan and develop your own butterfly garden or meadow or to learn more about our butterflies. Remember that both the Tarrant County Butterfly Society (see "More Info") and the Dallas County Lepidopterists' Society (see link below) meet monthly and often have field trips in which you are quite welcome to participate.
Butterfly Gardening for the South by Geyata Ajilvsgi. 1990. Taylor Publishing Company.
Butterflies of Houston and Southeast Texas by John and Gloria Tveten. 1996. University of Texas Press.
Butterflies through Binoculars: The West by Jeffrey Glassberg. 2001. Oxford University Press.
Four Wings and a Prayer by Sue Halpern. 2001. Random House.
Native Texas Plants by Sally Wasowski and Andy Wasowski. 1997. Gulf Publishing Company.
Texas Wildscapes: Gardening for Wildlife by Noreen Dalmude and Kelly Conrad Bender. 1999. Texas Parks and Wildlife Press.
http://www.dallasbutterflies.com/ -- excellent site of Dale Clark, local lepidopterist.
http://www.monarchwatch.org/ -- have a question about monarchs?
http://www.learner.org/jnorth/ -- answers to a trillion questions about monarchs. Most important, each spring they compile an updated map based on current sightings so that you can follow the migration of the monarchs north. They also map the journey south.
http://www.naba.org/ -- the North American Butterfly Association; much info.
http://forums.gardenweb.com/forums/butterfly/ -- some practical help on butterflies and gardening to attract them.
http://www.txcn.com/sharedcontent/features/texasgardener/BI_BUTTERFLY.6a12d05e.html -- garden guidelines by Charlene Rowell of Heard Museum and Tina Dombrowski of Texas Discovery Gardens.
http://www.texasdiscoverygardens.org/TopTenButterflyPlantlist.htm -- list of some useful host and nectar plants.
For more information, you may contact:
Tarrant County Butterfly Society (817) 923-8474
Joann Karges or (817) 923-8474
Henry Turner or (817) 922-9484