ABSTRACTS

Natural History, March, 1999 by Richard Milner

CATERPILLAR FEVER Insects that are parasitized may have few remedies available, but at least one kind of caterpillar--Platyprepia virginalis--seems to have evolved an amelioratire response. As Richard Karban, of the University of California, Davis, has discovered at the Bodega Reserve in Sonoma County, California, Platyprepia caterpillars that have been injected with the eggs of a tachinid fly often climb to the tops of dried vegetation, where they expose themselves to sunshine. The basking raises their body temperature, which Karban believes increases the caterpillar's chances of recovery. Heat may accelerate the development of the fly and encourage its early exit from the caterpillar, while the sun's ultraviolet radiation might help prevent infection in the exit wound. ("Caterpillar basking behavior and nonlethal parasitism by tachinid flies," Journal of Insect Behavior 23, 1998)

OTTER ANGLERS For countless generations, fishermen on the Ganges River have bred otters to chase fish into their nets. Pat Foster-Turley, of the White Oak Conservation Center in Yulee, Florida, visited the region to Learn about breeding otters--an undertaking the world's zoos have found very difficult. When working, the fishermen release the captive adult otters, tethered to long bamboo poles, to round up fish, while the cubs swim freely nearby. Successful breeding, Foster-Turley Learned, results from allowing the otters their choice of mates. "Otters were paired, split up, and re-paired through trades with other fishermen until, eventually, a compatible breeding pair was established, producing one litter a year for the rest of their lives." Once widespread, only a small number of otter fishermen survive in Bangladesh. ("Fishing with otters--a fading tradition," Oryx 32, 1998)

UNDERGROUND NET A forest is more than an aggregation of trees. Members of various species are linked by a group of subterranean fungi that live among their roots. Trees use these underground networks to share nutrients, conveyed by the fungi from one root system to another. Suzanne Simard, of the British Columbia Ministry of Forests, in Kamloops, and several collaborators, including David A. Perry, of Oregon State University, Corvallis, tracked the nutrient transfer with dual carbon isotopes, reporting that fir seedlings receive up to 10 percent of their fixed carbon from neighboring birch trees--an amount comparable to that received by young plants from their directly connected parental clones. Perry argues that such networks of mutual aid may evolve through natural selection, just as individual members of a species do. ("A moveable feast: the evolution of resource sharing in plant-fungus communities," Trees in Ecology and Evolution 13, 1998)

RAINFOREST HEADHUNTERS Among the more troublesome recent invaders of the southeastern United States have been the rapidly reproducing fire ants from South America, whose painful sting and mosquito-like bite have become notorious. What might slow down the relentless march of these ants, which have no natural enemies in the Northern Hemisphere? How about a little fly that would dive-bomb them and, within a tenth of a second, inject lethal torpedo-shaped eggs into their thorax--eggs whose pupae would decapitate the individual and then devour its head from inside? According to Sanford D. Porter of the U.S. Department of Agriculture in Gainesville, Florida, phorid flies from Brazil in the genus Pseudacteon do just that. Importing the flies, Porter opines, may cause fire ants to lose their competitive advantage, and their numbers should drop. Last summer, populations of the flies were established at several test sites in the southern United States, and researchers are monitoring their impact on the ants. ("Biology and behavior of Pseudacteon decapitating flies that parasitize Solenopsis fire ants," Florida Entomologist 81, 1998)

GENDER-BENDING GOBIES Some animals, such as earthworms, slugs, and snails, are noted for their ability to change sex. But Philip L. Munday and his co-workers at the James Cook University of North Queensland, Australia, have recently found a fish that not only can change from male to female--it can then change back again. This protean creature is a little goby (Gobiodon histrio) that lives among coral colonies off Lizard Island at Australia's Great Barrier Reef. At first, the scientists found single juveniles or male-female adult pairs. Closer investigation revealed that all the immature gobies were female. When additional mature females were introduced, some of them changed quickly into males. When two mature males were placed there and no females mated with them, some of the already transsexual males changed back to females. ("Bi-directional sex change in a coral-dwelling goby," Behavioral Ecology and Social Behavior 43, 1998).