Welcome to Firefly Keys. Our goal is to present information which will be of aid to on-line users in the identification of fireflies that they may make more accurate investigations, studies and research. We will do this by presenting links to published materials and sites on the Internet as well as photographs, drawings, or other material. It is also hoped that this presentation will make it possible for students, educators and amateurs to study fireflies in economically depressed areas, such that no longer will this occupation be limited to that class of society which can afford to attend the best colleges and universities or an education that is financially beyond the reach of all by a relatively few as college tuition costs skyrocket into the future. Original authors and contributors will be cited and given credit for their work. If you have drawings or photographs you would like to submit for consideration please send them to Dr. Firefly. Thank you for your contribution.
The accurate identification of fireflies requires close observation of their morphology and recording of mating flash patterns of the male firefly and female flash response.
With respect to North American fireflies a number of researchers have made significant contributions to recognizing and classifying the various species of fireflies; this includes: John L. LeConte, H. S. Barber, F. A. McDermott, John Wagener Green, and James E. Lloyd. Their classic works have been cited herein drawing illustratively from them to help educate and inform novices with respect to how to identify fireflies. It is hoped that by drawing together years of research a new generation of firefly enthusiasts will be born to continue more in depth studies in the future.
When one goes into the field to watch fireflies they are often met with a confusing mix of flashes; it took researchers many years to make sense out of the flashing fields, forests and meadow of fireflies; work in this regard still continues, for although some species of fireflies are relatively easy to come to recognize via their flash patterns and morphology, others are quite difficult to distinguish one from another.
In Photinus sp. it is necessary to collect a representative sample of a population and remove the genitalia by dissection; then to observe these in dorsal, lateral, and ventral views to compare to the structure of previously identified and referenced specimens. Standard methodology for the preparation of specimens for identification may be used:
A good quality dissection microscope is recommended for usage in the identification of fireflies. We recommend AmScope located in California, which provides a variety of high quality stereo-zoom dissecting microscopes as well as trinocular dissecting microscopes and digital cameras with software that can be used with the microscopes. The combination of dissecting microscope and digital camera is ideal in producing photographs to use in the presentation of keys to identify fireflies or other insects as well as for other educational purposes.
Specimen preparation for identificationThe identification of specimens usually requires males, and often the male genitalia need to be 'cleared' for examination. Clearing the male genitalia involves breaking off the abdomen and placing it in 10% potassium hydroxide (KOH; or sodium hydroxide, NaOH) solution. Most often, a cold KOH solution is used, with the specimens left overnight for clearing. Hot KOH can be used to clear specimens within a half hour, but KOH (particularly hot KOH) is caustic, and specimens are easily over-cleared if not carefully attended (not to mention that hot KOH may be dangerous). To break off the abdomen of a pointed specimen, turn the specimen upside down and push on the abdomen (to avoid damaging the genitalia, do not press on the pygofer); usually the abdomen will snap off at the base (at the tymbal mechanism), as long as the base of the abdomen is not covered with point glue. Sometimes the abdomen may suddenly snap off – it is a good idea to clean you workspace and perform this task within some type of container so that the abdomen can be easily found if abruptly dislodged. The abdomen can then be placed in KOH for clearing. When performing multiple dissections, be sure that the specimens and their abdomens can easily be associated without confusion later (usually by numbering the specimens and the clearing wells). A cleared abdomen will still have color, but will be flexible without being brittle. The soft parts of the anatomy will be easily dislodged and removed by gently tamping the abdomen. When the abdomen is ready to be removed from the KOH, place the abdomen in a water rinse and tamp out the abdomen contents to remove any remaining KOH (multiple rinses may be desired, or carefully neutralizing the KOH with a mild acid), then move the abdomen into glycerin. Sometimes the cleared abdomen will be sufficient to view the needed features, but often the aedeagus will need to be everted. This can be done by gently removing the pre-genital segments of the abdomen from the pygofer, then gently pushing the aedeagus with insect pins or a fine pointer from behind to evert it. Often the pygofer must be held in place while pushing on the base of the aedeagus. Considerable care should be taken to not tear the pygofer while pushing on the aedeagal base. When the aedeagus is everted, segment 10 (the "anal tube") will rotate anteriorly; sometimes rotating segment 10 will evert the aedeagus instead of pushing at the aedeagal base. When this process has been successfully completed, the aedeagus should be visible in lateral view, unobstructed by the pygofer (except possibly at the very base). TAL NOTES: The dissection of male firefly genitalia is best done using freshly collected specimens. Tools for this process can be made using pieces of razor blades that are broken off and mounted at the end of handles made using wooden matches, straws, or other material. One needs a steady hand and the aid of a dissecting or stereo microscope. After abdomens are removed, set in a small concave microscope slide with clearing agent. After mounting aedeagus upon a microscope slide in glycerin, drawings may be made with the aid of a drawing tube (Camera Lucida) which will project the image. A more modern method is to use a digital camera to photograph the aedeagus; then the digital image may be incorporated into graphic image software from which an illustration may be prepared. |
In Photuris sp. many species may only be distinguished by recording or noting their flash patterns. For other species it holds true that a close morphological examination coupled with an accurate recording of male and female courtship flash pattern is essential to establish an accurate identification.
In Fig. 9 above a drawing of the genitalia of a male Photinus pyralis is shown to illustrate the "key and lock" nature that is at play with respect to evolution in fireflies. The male genitalia may be thought of as a "key" which fits in and opens the "lock" to the female allowing copulation and insemination. Each species of firefly has a unique male "key" and female "lock" to permit sexual reproduction when the right male key finds the correct female lock. However, through the evolution of fireflies a wonderful method has evolved which enables the lock to be picked before inserting the key; this is the courtship flash behavior or dialogue between male and female fireflies. This ability to "pick the lock" through courtship flash behavior suggests that there is a genetic code key which determines the structure of the male and female genitalia; the nature of this genetic code key is probably such that courtship flash pattern is linked to the same gene which determines the structure of the male-female genitalia. This same gene may also be linked with the flight pattern behavior, such that when you modify the structure of this gene via variation, the modification causes the flash to vary, flight pattern to vary, and the genitalia to vary, such that over eons of time flash pattern and flight behavior alone has become linked to variations in genitalia that permit male and female to locate and recognize each other as mates suitable for a matrimony even though they have not made physical contact or consummated their marriage. In the case of Photuris sp. a more highly evolved genetic coding of flash behavior appears to be taking place, such that variations in flash pattern and/or flight behavior are occurring to enable speciation without dramatic variation in the male-female genitalia. Future genetic research should enable one to decipher the nature of the firefly gene such that it may be discovered how variation in the genetic code determines flash patter, flight pattern and genitalia structure; i.e., the relationship of morphological variation to behavior modification in fireflies.
When you combine description of the morphology of fireflies, including that of their genitalia, with their courtship flash behavior, one is able to best distinguish the various species which occur throughout a geological area. In cases where that geographical area is great, such as with Photinus pyralis (See Fig 10 below), there may be ecological niches where races or tribes of fireflies tend to form with similar gross morphological features, yet though mistaken for different species in the past, as in the case of P. benignus (LeConte), were found by Green's observation of genitalia to be P. pyralis none-the-less. Green also reported races of P. pyralus in the extreme southern tip regions of Texas, in the areas of Brownsville and Uvalde, which have gross morphological variations, but which have yet to vary in genitalia structure sufficiently to warrant being classified as new species.
In some species morphology alone is a significant indication of the species at hand or at least suggest what species of firefly one may be observing, as seen in the illustration below.
However, any accurate determination of species requires a more in depth review of the scientific literature describing species coupled with the same close observation of morphology and courtship flash behavior which was used by others to distinguish the various species in the first place.
During the early 20th century F. A. McDermott and H. S. Barber made extensive observations of the flash patterns of Photuris fireflies during their courtship and after collecting and examining specimens were able to distinguish new species revealing slight, yet common, morphological characteristics. This early work in what Dr. Lloyd later came to call "semiosymantics" or using signaling to identify a mate, illustrated that it is important to note both the flash behavior of fireflies and their morphology when classifying species. Barber even gave new names for some species of Photuris based upon the characteristic nature of their courtship flash patterns.
With rapid advances in genetics, it is even likely that one day in the not too distance future the easiest way to identify fireflies and many other species of insects which appear similar morphologically will be through molecular phylogenetics, which has already yielded insight into how light organs and signaling evolved in fireflies. Stanger-Hall 2007
This page is under construction. We will be adding additional information, material and links over time to help students, instructors and amateur naturalist learn how to identify fireflies so that they may participate in original research and make a significant contribution to the understanding of our natural world. We hope to inspire people everywhere around the world to become aware of fireflies and the need to preserve, conserve and protect not only fireflies but all species. Because fireflies flash during their courtship people notice them and become aware when fireflies disappear. Yet as fireflies disappear, so vanish many other insects and arthropods. People are not aware of the disappearance of many, many vanishing species because unlike fireflies they do not flash and glow. Fireflies thus serve as ALARM that something is wrong when they disappear. Learning how to recognize fireflies and study fireflies is therefore important, as this is a stepping stone to establishing "Firefly Safe Zones," which will aid in not only preserving firefly populations, but in saving and rescuing endangered and/or threatened species. Having health firefly populations around the world will also enable maintaining a health ecosystem for all species.
UOD 2010. Specimen preparation for identification. University of Delaware -- College of Agriculture & Natural Resources.
Credits: I wish to thank hessmuse@yahoo.com for assisting in the research for the preparation of this web site.