Guide to insects
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Last updated 08/15/2005
Insects of Coal Oil Point > Methods
Making a thorough collection of insects from an area as diverse as Coal Oil Point, while perhaps not rocket science, is more complicated than it might first appear. It certainly requires more than wandering around with a net, chasing bugs on the wing. A primary consideration is that all of the various habitat types will have specialist species found only in certain parts of the Reserve. So it was necessary to spend at least a little time specifically working in different areas. Secondly, only the most conspicuous insects can be casually netted. Most require a strategic approach, as well as a willingness to get a little dirty.
A couple of different types of traps were used in the survey. The most productive for flying insects was a Malaise trap. This tent-like trap, pictured at left, takes advantage of a tendency many flying insects have when encountering a barrier to grab it and climb. These insects are funneled upward into a bottle of alcohol at the apex of the trap. Over half of the insects we report here were collected by a single Malaise trap set in the backdune for about a month and a half in the spring of 2003.
Near this Malaise trap, and over the same time period, we set a single unbaited pitfall trap, shown at right. Pitfalls sample mostly flightless insects that fall into the trap while wandering. For a short time this trap was baited with a substance called cantharidin. Cantharidin is a natural defensive chemical produced by blister beetles (their name pretty well tells the story). A number of unusual insects are attracted to living or dead blister beetles, chewing or sucking on their bodies to obtain some of this chemical to use in their own defense. Though we have not yet found any blister beetles at Coal Oil Point, a number of these specialists were nonetheless attracted to cantharidin baits (see the beetle Notoxus lustrellus)
Collecting techniques additionally included sand sifting, vegetation beating, aquatic netting, and wrack combing. These general techniques have been used over a broader time frame than the trapping program described above, including sampling dates scattered throughout the year.
Altogether our samples represent approximately 45 trap-days, and an additional 25 person-hours of collecting effort at the Reserve. While this sounds like a lot, we estimate that we have as yet only documented somewhere between half to two-thirds of the actual insect fauna of the Reserve.SPECIMEN PREPARATION
The specimens, once collected, were brought back to the lab for preparation. While this primarily involved pinning or point mounting each individual specimen, many required some additional attention. Most flies (Diptera) and wasps (Hymenoptera) had been collected into alcohol. These fairly soft-bodied insects often shrivel when simply air dried. So these were subjected to a chemical drying process using HMDS (hexamethyl disilizane), which resulted in very nice specimens. These could then be glued to points. All specimens were labeled with precise collecting data, indicating where, when and how each specimen was collected. All 1783 prepared specimens are housed at the Santa Barbara Museum of Natural History.IDENTIFICATION
Obtaining and preparing this large collection of insects was a huge job. But it was only the beginning. The most daunting challenge in surveying insect biodiversity is figuring out what all has been collected. While field guides make identification of a few groups such as butterflies and dragonflies relatively straightforward, identification guides don't exist for the majority of insects, and those that do exist are rarely user-friendly. At present, we have in fact been able to identify only a small proportion of our collection to the species level. All specimens have been sorted to 'morphospecies', or groups of similar specimens that we believe to represent single species. But most of these have only been identified to the family or genus level. In some cases, we have gotten no further than 'midge' or 'tiny parasitic wasp'. This is partly a reflection of the state of insect taxonomy - even here in California, the work of specialists to fully catalog and produce guides to the fauna is far from done.
(Any specialists who see specimens pictured on this site that they'd like to study are welcomed and encouraged to contact collection curator Michael Caterino).
Disclaimers aside, a few books that we have found invaluable include:
The goal of this project was not just to catalog the insects of Coal Oil Point, but perhaps most importantly to be able to share this information with the world through this website. In order to do that we needed to photograph a specimen from each of our designated species. The museum already had pictures of the butterflies and some of the beetles on hand from previous projects, however with over 600 morphospecies in the collection this was still no small task.
The insects in the collection ranged in size anywhere from the six inch Black Witch moth to the tiny .01 inch Fairyflies. As a result of our subjects' great range in sizes we had to employ several techniques to properly photograph them. Most of the specimens were photographed using a Nikon D1x. Many insects in the collection were so small that they had to be photographed through a microscope. In these cases the Nikon was attached to a Leica MZ9.5 stereomicroscope, shown at right. The problem with taking a picture through a microscope is that it only focuses on one thin plane. For example, if the microscope is focused on the body of an insect, its wings, antennae, and legs will be quite blurry. In order to overcome this limitation we used a technique known as 'montaging'.
A mounted insect was positioned in clay on top of a gray board. A light diffuser fashioned out of a styrofoam cup, was placed around the specimen. The cup was modified into a "styrofoam spaceship" with two small holes on the side to let the fiber optic lights to illuminate the inside, and a larger hole on the top through which to view the specimen, apparatus shown at left. Several pictures were taken through the microscope. Usually 3-5 photos were taken at various planes of focus and then saved as tiff images. These images were then imported into a photo editing program called AutoMontage. The software incorporated the multiple images into one fully focused picture. We then manipulated this image in Adobe Photoshop 7.0, and converted it to the jpeg images you see on the site.
larger than about 1 cm were photographed with the same Nikon camera
through a macro lens. In this case, the camera was mounted above the
specimen, and mylar was used to difuse light, shown at left. In this case we were able
to take just one photo, which we then resized in Adobe Photoshop. This
method was used for a handful of insects in each order, for example the