Firefly egg and embryo gallery

The firefly egg and embryo gallery presents Photinus pyralis eggs photographed under a variety of lighting conditions for your enlightenment and enjoyment.

Figure C. Photomicrograph of P. pyralis egg from female collected 30 June 2001 in Montgomery, AL. The egg measures 0.825 mm in diameter and glows with a very dim green light.

Figure D. Like a microbal eclipse a firefly egg suspended in a droplet of water refracts light revealing a dark inner mass separated from the egg's outer pearl lustered shell, the formation of a larvae which glows bright green when disturbed by sharp vibrations. Oblong egg of P. pyralis 0.700 mm by 1.125mm with developing larva . Photo by Terry Lynch.

Figure E. Under dark field illumination egg of P. pyralis appears to glow brightly revealing an inner mass of dense cells as a firefly larva forms, pulling away from the egg shell encasement. While in fact firefly eggs do produce a dim glow which brightens as larvae develop, the effect shown here is due simply to refraction of light. Oblong egg of P. pyralis 0.700 mm by 1.125mm with developing larva . Photo by Terry Lynch.

Figure F. Egg of P. pyralis under dark field illumination shows debris adhering to the surface of the egg, central mass of cells and surrounding shell. This almost sphrical egg of P. pyralis is typical of those collected and measures 0.825 mm to 0.950 mm. Photo by Terry Lynch.

Figure G. Photinus pyralis egg viewed under dark field illumination shows green egg mass of developing larva and white area between larva and egg shell. Green hue added via photo enhancement. This is the same egg pictured in figure F and measures 0.825 mm to 0.950 mm. Photo by Terry Lynch.

Figure H. An embryonic larva of Photinus pyralis floats inside its spherical egg shell like a distant nebula amid galaxies of debris. This partially formed firefly larva measured 0.825 mm x 0.925 mm. Photomicrograph was taken with dark field illumination with firefly egg suspended in drop of water between slide and cover glass. A spacer ring was made using polyform modeling compound to avoid damaging the egg. Photo by Terry Lynch.

Figure I. Photinus pyralis larva almost fully formed rolled up inside egg with antennae and head visible at bottom. The egg pictured in figure I measures 0.775 mm to 1.025 mm. Photo by Terry Lynch.

Figure J. Photinus pyralis larva inside egg. Although blurred due to the thickness of the egg and contents which caused light diffusion under dark field illumination, the antennae, head, legs, segmentation and fiberous debris were all clearly visible to the eye when the focal plane was varied vertically. The egg pictured here is the same one shown in figure I and measures 0.775 mm to 1.025 mm. Photo by Terry Lynch.

Figure K. Photinus pyralis larva curled up inside egg. In this picture the segmentation of the curled larva is visible. It is also possible to distinguish the posterior end where the lantern and anal appendage occur and the antennae and head at the opposite anterior end. Movement of larva inside egg indicates an almost fully formed larva. Again this is the same larva/egg shown in figure I and measures 0.775 mm to 1.025 mm. Photo by Terry Lynch.

Figure L. This photo shows an embryonic Photinus pyralis larva with fully developed mandibles. Haziness is due to the fact that a thick egg, 0.825 mm to 1.050 mm, is being observed under dark field illumination. When focus was varied vertically, the observer could clearly see mandibles and legs which were both darkly colored and tanned at their tips. Larva movement inside egg revealed it exercising its mandibles, perhaps in preparation for chewing out of the egg. Photo by Terry Lynch.

Figure M. Prone to emerge from its egg like the eclipsed sun emerging from behind the moon, an embryonic P. pyralis larva exercises its sharp pointed mandibles and long pointed legs. One of two eye spots is also visible. Blur is due to scattering of light when egg suspended in water is observed under dark field illumination. Photo by Terry Lynch.

Figure 3. Optical microscope used to observe and photograph Photinus pyralis eggs and embryonic larvae. Inset: Left shows egg at 50X. Below egg on stage inside polyform ring between slide and cover glass is suspended in distilled water for observation and photographing. Photo by Terry Lynch.

This series of photomicrographs and observations of embryonic firefly larvae raises what perhaps is one of the most fundamental questions for future inquiry: at what point in larvae development does luminescence and its species specific control as seen in adults begin and how is this determined via genetic code? Do firefly sperm and/eggs glow prior to conception? If not, at what point after conception does luminescence begin?

Actually I was able to find the answer to this question via review of my own notes. In June of 1970 I experimented with infertile eggs of P. pyralis in my efforts to learn how to handle firefly eggs and how many eggs were inside females. Observations made in June 1970 indicate that P. pyralis eggs squeezed out of the abdomens of expired female's glow dimly but are not fertile as they do not develop and hatch into larvae. Eggs laid by female P. pyralis glow dimly and increase in their glow as the larvae inside obtains maturity. Hence cells within the egg are luminous even before fertilization but the egg can not develop and produce a larvae lantern until fertilized. Therefore it seems conclusive that eggs of P. pyralis contain luminous cells developed inside the female, indicating that a female firefly's genes contain the genetic key code for luminosity. The big question becomes: do both male and female contribute part of the genetic code required for lantern development in larvae and/or adults and control of flash patterns in adult fireflies, or does just the male or female contribute these lantern developmental and flash control genes? My guess is that this is contributed by both male and female given behavior variations contribute to speciation and such variations would occur in both male and female; plus, both male and female have a role in flash patten communication and recognition, so it only makes sense that the genes of both the male and female would contribute these factors.

Given that almost fully formed larvae inside eggs exhibit luminescence in response to vibrations, at what point in development of the firefly larva lantern is stimulus-response control enabled? How, in fact, is the lantern of a larvae constructed out of embryonic cells? What genetic code sequences actually control the growth and development of firefly larvae? What genetic code sequences control and determine each structure of a firefly larvae? Can that complex organism which is a firefly larva be better understood by retracing its development in the egg such that cellular changes which occur in the firefly larva embryo may give a better understanding of not just the larva lantern, but of the total organism? Finally, what is the genetic key code, or set of such codes, responsible for luminescence?

One approach of aid in answering some of these questions would be to make stained cross sections of firefly larvae eggs. Usage of appropriate stains will enable identification of luminescent cells or components. Cross sectional analysis of firefly eggs different ages may reveal much about how the larvae lantern comes into being. This should include growth and development of eggs within the female prior to fertilization (a difficult task given the problem of obtaining female fireflies of some species for study) and after fertilization.

In regards to the study of embryonic firefly larvae and lantern growth and development one may also want to consider bioluminescence of other organisms, even one celled animals and plants. For example, it is a well known fact that marine algae glow in response to vibration. Study of how light production in singles celled organisms occurs as a stimulus-response reaction may give clues to how light production in the more complex organ of a firefly larvae's lantern is enabled and controlled. The role of NO in enabling lantern flash of embryonic firefly larvae, should this be the case, may give clues to the development of light production organs and the nervous system of firefly larvae.

Although the embryonic development of any type of insect egg may be studied, firefly larvae eggs, or eggs of other luminescent species, may be of particular interest, as it will enable one to trace the development of light organs and their relationship to the nervous system and other organs, such as trachea. Then the study of firefly larvae pupation and metamorphosis may enable one to better understand how a simple larva light organ is transformed into the more complex light organ of an adult firefly.

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Copyright © 2001-2005 by Terry Lynch. All Rights Reserved. Please give credit where credit is due. If you want to use any of the photographs on this site as to publish them in books, articles or other web sites, please ask the author for permission. Also, this site is a report of original research, observation and experiment conducted over a period of years by the author. In any related investigations please site the author's works just as you would had it appeared in a scientific journal. Thank you.