Insects of Coal Oil Point > Methods
Methods
Sampling
Specimen preparation
Identification
Photography
SAMPLING
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:
-
An Introduction to the Study of Insects
by Donald Joyce Borror, Charles A. Triplehorn and Norman F. Johnson
find it
- The Flies of Western North America
by Frank R. Cole and Evert I. Schlinger find it!
- The Manual of Nearctic Diptera
by J. F Mcalpine
- Hymenoptera of the World: An Identification Guide to Families
by Henry Goulet, John T. Huber find it! (Hymenoptera guide to families)
- American Beetles Volumes I and II
by Michael C. Thomas and Ross H. Arnett Vol I, Vol II
- Butterflies of North America
by Jim P. Brock and Kenn Kaufman find it!
- Dragonflies and Damselflies of California
by Tim Manolis find it!
PHOTOGRAPHY
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.
Insects
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
bees.
Towards
the end
of the photography section of the project, the museum acquired a Canon
EOS 20D, with an MP-E65 1-5x macro lens. We were able to photograph
small insects that otherwise would have
needed to go through the microscope process in just one shot. All of non-insects, for example, were photgraphed this way. However, we still used a styrofoam light diffuser for most pictures.
|