Smithsonian Science » insects

How photography has transformed the study of spiders and their webs

John Barrat — Mon, 09 Jan 2012 12:32:22 +0000

Halocoryza acapulcana Whitehead

John Barrat — Wed, 19 Oct 2011 18:27:23 +0000

Halocoryza acapulcana Whitehead (Acapulco Saline Catarrh Beetle), described in 1966 by Donald R. Whitehead. This image is from a recent paper by Terry L. Erwin, entomologist at the Smithsonian’s National Museum of Natural History, containing updated information on this and two other previously described species of Halocoryza Alluaud beetles (sea-side beetles of the Indian, Atlantic and Pacific Oceans) and the description of a new species from Baja California Sur, Mexico, in the journal ZooKeys.

Invertebrates are ignored, overlooked by conservationists, policymakers and the public

John Barrat — Thu, 01 Sep 2011 15:22:31 +0000

When it comes to conservation, the earth’s invertebrates—insects, mollusks, worms, coral, arthropods and others—are getting a bad deal, say a team of scientists in a paper published recently in the journal Biological Conservation. Invertebrates make up more than 80 percent of all known species and provide humans with a myriad of valuable services—from crop pollination to their use as food—yet they are overlooked and underrepresented in conservation decisions and on priority lists of threatened and endangered species.

Image left: A honeybee pollinates and apple blossom.

“Invertebrate conservation is hard to justify when many people see each insect as a potential pest or each spider as a potential health threat,” write the paper’s authors, who include entomologists Terry Erwin and Pedro Cardoso of the Smithsonian’s National Museum of Natural History. In general the public is unaware of the critical role invertebrates play in the health of the ecosystem or the conservation threats that these creatures now face.

In addition, policymakers are often poorly informed about the details of invertebrate conservation, the scientists say. “Many assume that in protecting a single large animal, that animal will serve as an ‘umbrella species’ protecting all the other species—including invertebrates—in its habitat. “This view is however largely unsupported and untested,” the scientists say.

Image right: The tree-nesting tropical ant Cephalotes atratus (Stephen Yanoviak)

Remarkably, most of the world’s invertebrates remain unknown and have never been studied or described by scientists. The vast majority of species now going extinct due to human activities—about 3,000 a year—belong mainly to understudied groups of invertebrates, ‘the little things that run the world,’ the scientists write. “Because most invertebrates are undescribed, their geographic distribution is unknown as is their abundance, ways of life and sensitivities to pollution and habitat change.” Basic science for the study of invertebrates is scarce and underfunded.

Image left: Bonaire box jelly fish, St. Vincent Island, Caribbean (Photo by Ned DeLoach)

To remedy the problem the scientists offer a number of suggestions, including: More invertebrates should be placed on red lists of endangered species and in environmental impact statements; a stronger link must be made in the public imagination between invertebrate conservation and human well-being; sampling and analytical methods for biodiversity assessment and monitoring should be improved; and long-term ecological studies should be initiated to monitor ecosystem change.

“Invertebrate conservation is only possible with the preservation of ecosystems and their structure, function and processes,” the scientist’s conclude. “Only by preserving all species and guaranteeing interactions and ecosystem services may we reach the goal of overall biodiversity conservation.”

Photo right: A living colony of cupuladriid bryzoans, tiny coral-like marine organisms. (Photo by Aaron O’Dea)

“The seven impediments in invertebrate conservation and how to overcome them,” appeared in the journal Biological Conservation, and is authored by Pedro Cardoso, Terry Erwin, Paulo Borges of the Azorean Biodiversity Group, Portugal, and Tim New of La Trobe University, Australia.

Lofty experiments with gliding ants reveals secrets of their unusual flight

John Barrat — Mon, 13 Jun 2011 19:17:26 +0000

Since 2005 when biologist Stephen Yanoviak and his colleagues first reported that a species of tree-nesting tropical ant Cephalotes atratus, can glide backwards in a directed flight, the scientists have been studying this and other species of ants dropped from high places in Africa, Peru, Panama, Costa Rica and the United States. Seeking answers to the questions their 2005 discovery raised about the origin and evolution of flight in wingless ants, the researchers have used ropes, canopy walkways, construction towers, video cameras and even wind tunnels to conduct research on this previously unknown behavior in ants.

This short video shows frame-by-frame views of the movements of an ant (Cephalotes atratus) suspended in the updraft of a wind tunnel chamber. The three images are from above and two sides, and all are synched. These tree-dwelling ants are capable of a directed aerial descent (DAD) should they fall from high-up in the tree canopy. DAD is a defensive behavior that allows an ant to glide backwards and steer itself toward and land on the trunk of the tree from which it fell. In this way it is saved from the distant, hostile and unfamiliar terrain of the forest floor. (Video credit Yonatan Munk, UC Berkeley.)

Directed aerial descent (DAD) is a defensive behavior that allows an ant dislodged from the tree canopy to glide toward and land back on the trunk of the tree from which it fell. In this way it is saved from the distant, hostile and unfamiliar terrain of the forest floor.

This video was created to compare a non-gliding and a gliding ant, both dropped from a tree. Videos courtesy of Steve Yanoviak.

One of the most challenging aspects of this research is simply studying these insects as they are falling, says Yanoviak, a tropical arthropod ecologist at the University of Arkansas, Little Rock, and colleagues, Robert Dudley of the Smithsonian Tropical Research Institute, and Yonatan Munk, University of California, Berkeley. Small body size, rapid descent, and the long distances that they can fall, make accurate data taking a challenge, they write in a recent paper published in the journal of Integrative and Comparative Biology summarizing their research.

Still, the team has discovered many new and interesting aspects to the directed aerial descent of different species of ants:

• DAD has multiple evolutionary origins in ants, the researchers say, occurring independently in numerous genera in the subfamilies Myrmicinae, Formicinae and Pseudomyrmecinae.

• Wind tunnel videos reveal that as they fall, gliding C. atratus ants hold their legs elevated and outstretched above the main body, and their gaster (the bulbous posterior body segment) fixed slightly below the main body axis. This configuration is aerodynamically stable and creates a force that pushes the ant backwards in a controlled glide. These ants steer by changing the position of their hind legs, mid legs and gaster.

Images above and below: C. atratus by Stephen Yanoviak

• Ants with hind legs, mid legs and gaster removed are unable to steer or glide effectively.

• Only tree-nesting ant species are capable of directed aerial descent. Some species are capable of righting themselves as they fall and rotating so their heads point toward the trunk of the tree from which they fell, but are not capable of horizontal movement. This suggests a transitional period in which these ants are evolving a gliding behavior.

• Ground nesting ant species may forage in the tree canopy but they cannot glide.

• Morphologically, ant species that can glide look no different from ant species that cannot.

• Gliding ants that are active both day and night, cannot glide at night, mainly due to their inability to see a target in the darkness.

• Gliding ants that fall into the leaf litter or into water are frequently attacked and killed by other ants, insects and fish. The mortality of ants that fall to the forest floor varies depending on environment.

Given the wide diversity of arboreal ants in the world, the researchers say, a broader study of directed aerial descent in these social insects promises a deeper understanding of the origin and evolution of this unusual behavior.

Tropical Research Institute entomologist David Roubik talks about his life as a scientist based in Panama

John Barrat — Wed, 20 Apr 2011 18:53:52 +0000

"I'm getting paid to do what I like doing," says entomologist David Roubik. He loved nature and being outdoors when he was a kid, and now he does fieldwork in the tropical forests of Panama. He loves to travel, and his research takes him around the world. Can his work, then, be called a job? Related posts:

Video: Community ecologist Sunshine Van Bael explains her work in Panama with leafcutting ants

John Barrat — Sun, 03 Apr 2011 15:42:48 +0000

From chewing tough insects to soft fruit, bat teeth are highly specialized

John Barrat — Tue, 22 Feb 2011 14:55:06 +0000

In a clever use of GPS technology, biologists at the University of Massachusetts Amherst have “mapped” the topography of bat teeth as if they were uncharted mountain ranges, in order to better understand how toothy ridges, peaks and valleys have evolved to allow different species to eat everything from hard-shelled insects to blood and nectar.

Image right: The faces and upper teeth of bats that eat insects (top), fruit (bottom) and a combination of fruit and insects (middle). (Image credit: Sharlene Santana)

Using a method based on geographic positioning systems that allows them to characterize the topography of the bats’ molars in a way similar to how geographers characterize mountain surfaces, the researchers calculated a measure of dental complexity that reflects how “rugged” the surface of the tooth is. Their work was supported in part through a predoctoral fellowship from the Smithsonian Tropical Research Institute.

Working with field-collected bat skulls, researchers Sharlene Santana and Betsy Dumont of the University of Massachusetts, with Suzanne Strait of Marshall University, compared the structure of molars across 17 species of the New World leaf-nosed bats that specialize in a variety of different diets (insects, fruits, and a combination).

They found that the molars of fruit-eating species had sharp outer edges that likely allow them to pierce tough fruit skin and pulp, plus large surfaces with tiny indentations that may help them grind fruit pulp efficiently. By contrast, the molars of insect-eating species were less complex, possibly because of their smoother shearing surfaces. The more simply-shaped teeth would presumably be good for cutting through hard insect exoskeleton. A paper on their research was published in the journal Functional Ecology.

Video: Three views of bat teeth in species specialized for different diets. First, fruit eaters have broad chewing teeth with many tiny bumps (Artibeus jamaicensis), while the second set of teeth, in an insect eater, show more ridges (Micronycteris hirsuta). Finally, teeth of a species that eats both fruit and insects have the tallest and simplest chewing tools (Phyllostomus hastatus). Video courtesy www.biomesh.org.

The researchers further tested if, within insect-eating species, higher molar complexity was related to a greater ability to crush insect prey. They fed beetles to field-caught bats, recorded their feeding behavior, then collected fecal samples to measure how well the beetles had been broken down. “We found that insect-eating bats with more complex molars were better at breaking down prey, but how much bats chewed their prey was also important,” Santana and colleagues say.

“Our study highlights the functional significance of tooth structure and chewing behavior in breaking down natural prey and…..provides a major step forward in understanding mammalian feeding systems,” the researchers say. –Janet Lathrop, University of Massachusetts

“Billy club” leaf beetle has been hiding in Smithsonian collections since 1959

John Barrat — Wed, 16 Feb 2011 14:56:23 +0000

A new species of Brazilian leaf beetle named Cachiporra extremaglobosa, (which translated means the “extremely globular billy club leaf beetle,”) was recently discovered by scientists at the Smithsonian’s National Museum of Natural History. Its name alludes to the club-shaped antennae found on its head. The beetle measures roughly 1.85 millimeters in length and is commonly found on the bark and foliage of trees. The billy club leaf beetle was discovered in a large collection of insects acquired by the Smithsonian in 1959 from the late Argentinean beetle expert Francisco de Asis Monrós.

Image above: Four different perspectives of Cachiporra extremaglobosa. Image left: This view of C. extremaglobosa shows its club-shaped antennae.

“This beetle represents a new species, genus and tribe,” says entomologist Maria Lourdes Chamorro, who described the insect with Smithsonian colleague Alexander Konstantinov, from the U.S. Department of Agriculture. Chamorro came upon the beetle while going through a drawer of beetles from a different subfamily, the Cryptocephalinae. “When I saw the clubbed antennae I almost fell off my chair,” Chamorro recalls. She knew instantly the beetle was misplaced. “Usually in leaf beetles the club shape of the antennae is gradual but the club shape of this beetle starts at the eighth antennal segment (most leaf beetles have 11 antennal segments.).” Other members of its subfamily Lamprosomatinae are beautifully metallic in color. C. extremaglobosa is black with bluish-bronze luster.

Leaf beetles do not use their antennae as clubs but as a “nose,” Chamorro says, to detect pheromones from other leaf beetles and to recognize its host trees. “We don’t know why its antennae are shaped like clubs.” A paper describing C. extremaglobosa was published in a recent issue of the journal Zookeys.

With specialist pollinator absent, Himalayan gingers must adapt

John Barrat — Thu, 13 Jan 2011 21:05:44 +0000

The insect’s absence was conspicuous for botanists studying the reproduction of two little-known gingers—Roscoea cautleoides and Roscoea humeana—in the Himalayan Mountains of China. During three different years from early May to late June the Chinese and American scientists waited for a special pollinator to appear and sip nectar from the gingers’ flowers. They were expecting a fly or moth with a long, specialized tongue; one that fit down the deep, narrow corolla tubes of the ginger blossoms. The scientists staked out dozens of the gingers night and day while the plants flowered, but no long-proboscid pollinator ever appeared. Climate change, they surmised, was responsible for the loss of this highly specialized and now, perhaps forever unknown insect.

Although the breakdown of such a mutualistic relationship can have devastating consequences for a plant species, these gingers were adapting, the researchers observed. Remarkably, they found, the flowers of the two ginger species remained viable for 6 to 8 days, the greatest longevity of any known ginger flower. On average ginger blooms last one day only.

Such an adaptation increased the probability that other insects would pollinate these flowers. Forging short-tongued bees, the botanists observed, were one of the few insects that visited the gingers and occasionally pollinated them.

Images right: Clockwise top right: R. cautleoides; R. humeana; short tongued pollen collecting bee on an R. cautleoides flower; short-tongued pollen collecting bee on R. humeana flower; the flowers of R. cautleoides (right) and R. humeana (left) showing their long, narrow corolla tubes.

Although the loss of their specialized pollinator is a serious blow to R. cautleoides and R. humeana, “our study represents a striking example that compensatory floral mechanisms help to ensure reproductive success in light of the apparent loss of specialized pollinators,” the researchers write in the journal Plant Biology.

A paper on this research, co-authored by John Kress of the Smithsonian’s National Museum of Natural History; Z.-Q. Zhang, P.-Y. Ren, J.-Y. Gao and Q.-J. Li, of the Chinese Academy of Sciences; and W. –J. Xie of the Yunnan Academy of Agricultural Sciences, was published recently in Plant Biology, a journal of the German Botanical Society and the Royal Botanical Society of the Netherlands.–John Barrat

Cool science is being carried out on a Smithsonian island in the Panama Canal

John Barrat — Mon, 06 Dec 2010 13:47:45 +0000