1
17 December 2011 | NewScientist | 17 Don’t let the cave bedbugs bite After a hard day hunting and gathering, humans 77,000 years ago could count on a good night’s mosquito-free sleep on a comfy bed of grass and leaves. We know this because their bedding has been found in a South African cave. People lived in Sidubu cave from 80,000 to 38,000 years ago. A team led by Lyn Wadley of the University of the Witwatersrand in Johannesburg, South Africa, has now found layers of grasses, sedges and rushes on the floor of the cave, dating from 77,000 years ago onwards. they say it was most likely bedding – the oldest example ever found. All layers younger than 73,000 years show signs of burning, which Wadley suggests may have been routinely done to kill pests and diseases (Science, DOI: 10.1126/science.1213317). Not only that, the prehistoric homemakers also carefully chose their bedding for its medicinal properties. Although a range of trees grow in the region, they only used the Cape laurel (Cryptocarya woodii), which repels insects – including malarial mosquitoes – and their larvae. that makes the bedding the first sign of humans using medicinal plants, too. City lights show where to send measles vaccine MeASLeS hits migrating people when they crowd together. the good news is that it is possible to tell exactly where that is – and where to aim vaccination – by looking from space for the glow of the migrants’ lights. In 2008, after a vaccination programme had led to a global decline in deaths from the disease, measles bounced back. A resurgence among poor west African migrants, who tend to congregate during winter dry seasons, is a particular concern. However, because the virus also survives better in drier weather, it was hard to tell whether the crowding was the real problem. Nita Bharti at Princeton University and colleagues have now teased apart the variables of crowding and weather by scrutinising satellite images for the glow of people’s night-time fires and electric lights (Science, DOI: 10.1126/science.1210554). In poor regions, night-time glow reveals population density, so Bharti’s team used satellite images to map dry-season illumination increases in cities WHO would have thought it? An insect that spends all its time in bed with its siblings enjoys inbreeding. Coby Schal at North Carolina State University in Raleigh studied the genetic diversity of bedbugs (Cimex lectularius) in US buildings. He found that it was so low that in some cases a building-wide infestation may have originated from one pregnant female. Inbreeding is usually bad news for offspring because they are more likely to display genetic defects hidden in the recessive genes of their parents. Bedbugs – and a few other insects including cockroaches – are an exception. Some inbred populations may already be on their 70th generation, Schal told a meeting of the American Society of Tropical Medicine and Hygiene in Philadelphia, Pennsylvania, last week. That suggests inbreeding might not be a weakness we can use to eradicate the pests, he says. Rajeev Vaidyanathan at SRI International in Menlo Park, California, agrees. Most people already know the best way to tackle the pests, he says. “I don’t want to sound like your mother, but eliminate the clutter in your rooms and vacuum a lot.” Bedding down for some inbreeding DENNIS KUNKEL MICROSCOPY, INC./VISUALS UNLIMITED, INC./CORBIS in Niger after dark. In three cities, the brighter periods coincided with recorded measles outbreaks. In a fourth, with similar weather but little seasonal migration, there was no increase in either glow or measles. Claude Muller of the Institute of Immunology in Luxembourg says the insight into what makes measles seasonal is important. “If we understand that better, we can target vaccination better, to make sure less virus gets through the off season,” which could help to eradicate the disease, he says. Ultra-flat cells give buttercup its glow A BUTTERCUP’S chin-brightening yellow glow is more than child’s play – it gives the flower a competitive edge in attracting pollinators. But what causes this buttery gleam? Ullrich Steiner, at the University of Cambridge, and colleagues separated the layers that make up buttercup petals – an inner layer of starch and an outer epidermal layer that holds the yellow pigment – and shone light onto each. The starch layer reflected light like a rose petal, diffusing rays in many directions. The key to the buttercup’s glow seems to lie in the exceptionally flat cells of its epidermal layer. Steiner’s team found that light bounced off these cells in the opposite angle to which it hit the petal, like a flat mirror. This directed light creates an intense glow not seen if you hold another flower to your chin (Journal of the Royal Society Interface, DOI: 10.1098/rsif.2011.0759). Magnifying this effect is an air pocket between epidermal and starch layers, the team also found. This keeps a portion of the incoming light from reaching the starch layer, ensuring that it is reflected in a directional manner by the flat cells at the base of the epidermal layer. The reflectivity was the same for ultraviolet light, which bees use to navigate. As the buttercup sways in the wind, its petals flash like neon signs advertising its pollen. JASON GALLIER / ALAMY For new stories every day, visit newscientist.com/news
