Fall 2007 Issue
Need to identify a species of the insects known as cicadas? If BU’s Dr. Allen Sanborn isn’t available, you might be out of luck.
By Paige Stein PStein@barry.edu
How many of us can say we are the only person on the entire continent – and one of the few in the world – who do what we do? Even the top neurosurgeons or biomechanical engineers among us would have a hard time laying claim to that distinction.
But for Dr. Allen Sanborn, a Barry University professor of Natural and Health Sciences and an expert in identifying and classifying species of insects known as cicadas, it’s nothing out of the ordinary.
“I’m pretty much it for the new world,” he said.
In fact, Sanborn, who says he was definitely not one of those kids who loved bugs, fell into studying cicadas, an insect related to leafhoppers and spittlebugs, by accident. As a master’s candidate at the University of Illinois at Urbana-Champaign, he was looking around for a thesis project involving scanning electron microscopy. An electron microscope uses electrons rather than light to form an image allowing it to produce high-resolution images of a sample surface.
“One of my graduate school instructors was very interested in having me apply the technology to cicadas,” said Sanborn, who added that it was the field work that really got him hooked.
Initially interested in thermal biology and acoustics, Sanborn got involved in taxonomy, the scientific classification of plants and animals, simply because there was no one else around to do it.
“I basically had to teach myself taxonomy,” he said.
There are, according to Sanborn, at least 2,000 unidentified species of the common, but under-researched insect sitting in labs and archives across the country. About 3,000, he estimates, have already been described.
Sanborn has published the descriptions of 11 species: two in 2004, five in 2005, two in 2006 and two as of June, 2007. He also has individuals of 50 new species, which add up to several hundred specimens, just sitting around his lab waiting to be described and identified, he says.
“As fast as I can identify them and write them up, I publish them,” he said.
Describing and identifying a cicada can involve anything from measuring their wing span, to comparing genitalia, to recording their songs.
May 2007 graduate Ana Poeck worked in Sanborn’s lab, helping to gather data on cicada specimens, an endeavor which, she says, was rewarding but required a lot of patience.
“First, I helped with measuring the cicadas’ wing and body length, and then I started softening them to trace the wings. Their exoskeleton is hard and the wings are close to the body, so to open the wings to be able to trace them, you have to soften them first,” said Poeck, who entered the University of Pennsylvania School of Veterinary Medicine this fall. “After tracing the wings on paper, I use a special computer program to get the wing area. You definitely need patience. Tracing cicadas and measuring them takes a lot of time, and you have to be really careful because they are so delicate.”
Cicada experts: an endangered species
And how is a cicada determined to be of a different species and not merely a variation of existing species?
Through the process of elimination, Sanborn says. A cicada’s characteristics direct him to a specific genus or taxonomic group, which allows him to eliminate all species that have already been described.
After he makes the determination that this is, in fact, “something new,” he sends a paper on his findings, often accompanied by a photo or student drawings of the specimen, to various academic journals. They, in turn, send the paper to other experts or academics for review. After they critique it, and any additions or changes are made, the revised paper is then resubmitted. Once it has been accepted and published, a new species of cicada is “born.”
The list of colleagues around the world, those capable of reviewing Sanborn’s work and confirming the identification of new species, continues to shrink.
“There aren’t that many of us left, most of the people who study cicadas are retired,” said Sanborn, reciting the short list of the world’s retired or semi-retired cicada experts, including Michel Boulard, a recently retired French cicada expert who has described more species of cicadas than anyone else.
Sanborn, himself, has been on field expeditions all over the world including, Costa Rica, Argentina and South Africa. Domestically, his work often takes him to the Southwest where there’s a “greater diversity of plant and animal life, and the trees are shorter.”
“I’ve had to see the Grand Canyon 17 times,” jokes Sanborn, who cited a trip to Pena Blanca in Southern Arizona as illustrative of the combination of luck, patience, and determination that successful field work requires.
“Pena Blanca is a location where we knew a rare species, Cornuplura nigroalbata, had been found,” he explained. “I went with my graduate advisors and on my own six separate times without collecting a single specimen. Then, on an expedition in 1991, we were able to collect more than all the previously known specimens. So in that one trip we more than doubled the number of specimens that had ever been collected.”
Getting to know you
Sanborn is often accompanied on his field expeditions by his wife, Dr. Polly Phillips, who teaches human biology, physiology and entomology at Florida International University in Miami. The couple, who have co-published 20 papers and made 26 joint presentations on their cicada work, went on their first field expedition together as graduate students at the University of Illinois.
“I joined the same research lab as Al (Sanborn) as a biology master’s student in 1988. There were four of us in the lab. We all worked on different animals, but the common theme in the lab was temperature/thermal biology,” Phillips said. “Each year [the lab] mounted a cicada field expedition. Since Al was the one working on cicadas, he went every summer, but they always took another student in the field. So that’s how I began the cicada stuff.”
Getting to know cicadas over the years, while always interesting, Phillips says, hasn’t always been accommodating.
“The technique is to drive with the windows down and listen for the calls, then to stop and go looking. Since these bugs are active in mid-summer, it can mean driving without air conditioners, or radios, in 100-plus Fahrenheit heat,” she said.
Although he once hung “off the side of a cliff” trying to capture a new specimen, Sanborn finds many of his specimens “hiding” in lab shelves rather than under a tree. During a visit to North Carolina Sate University in 2003, Sanborn identified two new species from China while studying the university’s North American specimens.
Neotanna shensiensis and Termpnosia shaanxiensis were collected in Shaanxi province in 1939 and had been sitting in the university’s archives for years before Sanborn identified them and published his findings in Acta Entomologica Sinica, a peer-reviewed Chinese and English bilingual journal, co-sponsored by the Institute of Zoology, the Chinese Academy of Sciences and the Entomological Society of China.
“There were 24 species previously known from the province. I added two more,” he said. “Shaanxi has several mountain ranges that pass through it, providing areas that can lead to reproductive isolation of populations and the formation of new species. Thirty percent of the species found in the province are found nowhere else.”
Last year alone Sanborn received identification requests from 16 universities, four museums and/or collections and 18 individuals.
“When Al begins to work on the bugs, he’s relentless and rarely takes a break. I’m aware of that, so if we are visiting a museum, I can expect not to get a lunch break, if he really wants to finish the work that day,” Phillips said. “I can handle that because I force him to do other non-cicada stuff whenever we travel.”
No pests allowed
Despite the backlog of specimens waiting to be identified, cicadas, partly due to their size, are typically underrepresented in collections around the world, Sanborn says.
“The use of portable generators, mercury vapors and black light traps has led to a significant increase in cicadas being collected. However, there is still prejudice among many entomologists as they discard the cicadas at traps because they are so large in comparison to be the majority of insects and take up valuable space in limited transport.”
Another reason why the cicada isn’t studied more frequently could be related to the fact that while it may be a little noisy, it’s not really much of a pest – at least in agricultural terms.
“Basically cicadas are not agricultural pests. They don’t threaten our crops or eat what we eat, nor do they bite or sting humans, so people tend to forget about them,” he said.
Not only does the cicada not eat what we eat, it doesn’t eat what most other insects eat.
“Cicadas are smart because they exist off the xylem, food compartments in the plant which are mainly water. Xylem is a nutritionally poor substance. Many insects and other organisms subsist on the phloem, the part of the plant where most of the nutrients are found.”
Singing in the rain
While the 17-year cicada (the kind that has caused communities in the Midwest to put out dumpsters marked, ‘For Cicadas Only’) is probably the most well known in the United States, the average life-cycle for a cicada is two to five years.
After mating, the female deposits her eggs in twigs or grasses depending on the species. When the eggs hatch, the newborn nymphs drop to the ground and burrow in at depths ranging from a foot to about 8 1/2 feet.
“Cicadas spend a total of about three weeks above ground in their entire life. The rest of the time they spend as an egg or underground [as a nymph],” Sanborn explained.
When they’re ready to emerge as adults, they burrow to the surface and molt, often leaving their skins on nearby tree branches.
At that point it’s all over, but the singing.
Most cicadas produce sound through timbals, or paired membranes located in the abdomen. When the timbals contract, they make a pulse of sound; the male’s abdomen is basically hollow, allowing the sound to resonate.
“It’s basically a mating call, which males use to attract a female,” said Sanborn. “The songs of cicadas act as reproductive isolating mechanisms…The females are attracted preferentially to the calling song produced by the males of their own species. This prevents cross-mating and potentially wasting their only chance to reproduce.”
Sanborn uses a portable tape recorder to record cicada songs in the field before analyzing them in his lab and, when possible, comparing them to a catalogue of existing songs.
“I have computer programs in the lab that digitize the sound and allow me to determine the frequency components and temporal parameters of the song. These differences can then be used to determine the status of a group as a species or not,” said Sanborn, who added that this technique was used to determine that what had been described as a variety of cicada in western Texas was, in fact, a species. (The term ‘variety’ is used to describe individuals that differ from the remainder of the species in certain minor characteristics.)
“We were able to show this population had a unique strong structure and elevated the variety to a species,” he said.
Brave ‘new’ world
In addition to continuing to refine classifications of cicadas, these days Sanborn and Phillips are also interested in the biogeographical patterns of cicadas.
“The big biogeography of Northern American cicadas, which involves trying to associate individual species with host plants, is taking most of our collaborative time these days,” Phillips said. “Al does the identifications when we visit the various museum collections. I am responsible for compiling and maintaining the collection location data and, ultimately, I will make the maps.”
And while Sanborn continues to work to identify species as fast as he can, it’s not likely he can keep pace with the sheer volume of specimens being collected.
“As more expeditions move into unsampled tropical areas, more new species are being discovered. I have more than 20 new species from Ecuador, Peru and French Guiana sitting in the lab,” said Sanborn, who noted that while new species are being discovered in both tropical and temperate regions, species are also disappearing in parts of the United States.
“Sadly, some broods (year classes of periodical cicadas) are disappearing, especially in New England where their habitats are being eliminated,” he said. “Even though there can be up to 3 million per acre, people still destroy their habitat by getting rid of trees and eliminating food.”
But Sanborn and others in the field may soon be getting some help identifying cicadas, thanks to the Partnerships for Expertise in Taxonomy (PEET) project. Funded by a grant from the National Science Foundation, the project seeks to “enhance taxonomic research and help prepare future generations of experts” by supporting research projects that “target groups of poorly known organisms.”
Projects must “train new taxonomists (a minimum of two per project) and must translate current expertise into electronic databases and other products with broad accessibility to the scientific community.”
“Basically, there was a period from the 1970s through the 1990s when taxonomy fell out of favor for funding, so no one was being trained to do it. I had to teach myself, because there was no one who could do it for the group that I use in my research,” said Sanborn, who serves as a senior faculty member on one of the PEET projects by identifying cicadas and helping students who are working on them.
In the meantime, while waiting for the next generation of cicada specialists to emerge, Sanborn is happy to continue working in his lab, making inroads on the long list of specimens just waiting to be identified.
“I really like being the one to see something new, something that no one’s ever seen before,” he said.