Photo Slices Provide Detailed Images of Tiny Wasps for Biocontrol Efforts
Using specialized digital photography methods, USDA scientists are producing high-resolution images of members of the wasp superfamily Platygastroidea.
According to Elijah Talamas, a postdoctoral scientist with the USDA’s Agricultural Research Service (ARS), the photographic process begins with positioning a wasp specimen under a specialized camera with a single-column lens attached to a vertical joist, and then taking stacks of photographs throughout the depth of the specimen.
Each photograph contains a small part of the insect in focus due to the small depth of field at high magnification. The “slices” are then combined into a single, highly-detailed digital image magnified up to 100 times the specimen’s original size. The image is then uploaded to online databases operated by university cooperators and linked to interactive keys, which guide users to specimen descriptions and other information.
“Making the images freely available online makes it possible for anyone with an Internet connection to assess the morphology of the holotype specimens,” said Talamas. “Each specimen has a unique collecting unit identifier (CUID) — which allows a user to determine the specimen’s origin on a species-distribution map. Taxonomists can refer to a particular specimen via its CUID without ambiguity.”
Of particular interest is using the images to improve the identification and taxonomic description of one- to two-millimeter-long Trissolcus wasp species that parasitize stink bugs and could have potential as biological control agents. The wasps’ larvae hatch and feed inside the bug’s eggs, killing them in the process. Some species attack the eggs of the brown marmorated stink bug (BMSB), an invasive pest from Asia that’s become established in 39 states and, in 2010, inflicted $37 million in damage to corn, soybeans, grapes, and other crops.
“One of the challenges of taxonomy for such small creatures is that taxonomists have had to rely on written descriptions and illustrations to understand what they have not seen firsthand,” Talamas explained. “In some cases this has worked very well, and high-quality illustrations are extremely useful. However, illustrators simply cannot capture all of the detail that a photograph can.”
The efforts of Dr. Talamas provide valuable taxonomic support to ARS researchers in Newark, Delaware, who are examining the host specificity and safety of several Asian Trissolcus species for potential use in biocontrol release programs against the BMSB.
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