James E. Lloyd

Aggressive Mimicry in Photuris: Firefly Femmes Fatales

Firefly females of the genus Photuris, long known to be carnivorous, attract and devour males of the genus Photinus by mimicking the flash-responses of Photinus females. Although suspected, this behavior had not been observed previously.

Ecology of Colors of Firefly Bioluminescence

Dark-active North American fireflies emit green bioluminescence and dusk-active species emit yellow, in general. Yellow light and yellow visual spectral sensitivity may be adaptations to increase the signal-to-noise (that is, foliage-reflected ambient light) ratio for sexual signaling during twilight. The peaks of the electroretinogram visual spectral sensitivities of four species tested, two dark- and two dusk-active, correspond with the peak of their bioluminescent emissions.

Aggressive Mimicry in Photuris Fireflies: Signal Repertoires by Femmes Fatales

Females of Photuris versicolor prey on males of other species by mimicking the flash responses of the preys own females. They adjust their responses according to the male pattern, and attract males of four species with distinctively different flashed responses. The capabilities of the firefly brain are more complex than previously suspected. The mimicry is quite effective, and females seldom answered more than ten males without catching one.

THE COLORS OF FIREFLY BIOLUMINESCENCE—I. OPTIMIZATION MODEL

Abstract— A model is developed for the optimization of signal‐to‐noise ratio for the detection of bioluminescence by fireflies during twilight. The relative degree of optimization is derived in terms of a dimensionless ratio, a biologically effective adaptation. The numerical values of this adaptation can be used to predict the sequence of adaptations of both visual spectral sensitivities and bioluminescence spectral emissions that result in the range of colors of bioluminescence of fireflics from green through yellow. It is shown that a narrowing of visual spectral sensitivity via a screening pigment pathway in order to discriminate against green ambient light is more efficient than a shift in visual spectral sensitivity via change in the opsin photoprotein. The model predicts that the range of wavelengths for the peak intensities of bioluminescence for North American fireflies should be between 550 and 580 nm and provides the physical basis for the observations that in general dark‐active firefly species cmit green bioluminescence and twilight‐active firefly species emit yellow bioluminescence.

THE COLORS OF FIREFLY BIOLUMINESCENCE—II EXPERIMENTAL EVIDENCE FOR THE OPTIMIZATION MODEL*

Abstract— The shapes, the peak wavelengths and the close matching of bioluminescence colors to visual spectral sensitivities in North American firefly species are consistent with the predictions of a spectral optimization model for selection in evolution (Seliger et al., 1982). A screening pigment found by microspectrophotometry in the rhabomeres of Photinus pyralis has the absorbancc characteristics predicted by the model. The biologically effective adaptation, a dimensionless ratio proportional to the relative advantage of a species to detect bioluminescence during twilight. has been calculated from experimentally determined distributions of ambient spectral radiances, visual spectral sensitivities and bioluminescence emissions and is shown to correlate both with color of bioluminescence and with the timing of initiation of flashing activity. The colors of firefly bioluminescence are therefore species‐specific adaptations to optimize the detection of bioluminescence in the different photic environments in which the species have evolved.

Flashes of Photuris Fireflies: Their Value and Use in Recognizing Species

Mating flashes provide excellent clues for recognizing biological species of fireflies. Since Photuris species also flash in contexts in which species-specificity would appear to be irrelevant, mating flashes must be distinguished; since the parameters of mating flashes that do not encode species information may vary considerably, these signals must be critically analyzed. The use of mating flashes for species recognition has spatial and temporal limitations.

OCCURRENCE OF AGGRESSIVE MIMICRY IN FIREFLIES

Predation by aggressive mimicry in fireflies is known only in females of the Photuris pennsylvanica-versicolor group (it is doubtful that fireflies in the other group of the genus, i.e. P. congener and relatives, are predators as adults). Aggressive mimicry has been observed in 10 species, and circumstantial evidence suggests that such predation probably occurs in all species of the pennsylvanica-versicolor group, though there could be idiosyncratic exceptions. Probably most species prey on 2 or more species: P. versicolor preys on at least 11. Males and larvae of some Photuris spp. may also be aggressive mimics, but evidence is only suggestive.

Symposium: Insect Behavioral Ecology--'82: Male Competition in Pteroptyx Fireflies: Wing-Cover Clamps, Female Anatomy, and Mating Plugs

A variety of male insect structures are used to hold females during mating including mandibles (Sivinski 1981), tergal gin traps (pinching organs) (Morris 1979), genital claspers (Wing 1982), antennae and modified legs (Parker 1970). Such structures may prevent other males from taking over a receptive female (Parker 1970), and they may enable the male to manipulate the female to his advantage-e.g. for forceful insemination (Thornhill 1982; see also, Lloyd 1979). The hooked elytral tips of Pteroptyx fireflies, long a puzzle to biologists who observed them and also the primary criterion for separating the genus Pteroptyx from Luciola, are used to clamp the female during mating in Pteroptyx valida, and probably other species. Here we present the details of this clamping as it occurs in P. Valida.

Flash signal evolution in Photinus fireflies: Character displacement and signal exploitation in a visual communication system

Animal communication is an intriguing topic in evolutionary biology. In this comprehensive study of visual signal evolution, we used a phylogenetic approach to study the evolution of the flash communication system of North American fireflies. The North American firefly genus Photinus contains 35 described species with simple ON–OFF visual signals, and information on habitat types, sympatric congeners, and predators. This makes them an ideal study system to test hypotheses on the evolution of male and female visual signal traits. Our analysis of 34 Photinus species suggests two temporal pattern generators: one for flash duration and one for flash intervals. Reproductive character displacement was a main factor for signal divergence in male flash duration among sympatric Photinus species. Male flash pattern intervals (i.e., the duration of the dark periods between signals) were positively correlated with the number of sympatric Photuris fireflies, which include predators of Photinus. Females of different Photinus species differ in their response preferences to male traits. As in other communication systems, firefly male sexual signals seem to be a compromise between optimizing mating success (sexual selection) and minimizing predation risk (natural selection). An integrative model for Photinus signal evolution is proposed.

Spectral sensitivity of the compound eyes in two day-active fireflies (Coleoptera: Lampyridae: Lucidota)

SummaryThe electroretinographic visual spectral sensitivity functions in day-active fireflies Lucidota luteicollis and Lucidota atra show a broad green sensitivity and a shoulder in the near-ultraviolet region of the spectrum (Figs. 1, 2) as is commonly found among day-active insects. The nomogram for P530 visual pigment matches the spectral sensitivity curves in the green. The adult L. luteicollis retains its larval bioluminescent light organ which has a peak emission at 562 nm. The λmax of the ERG spectral sensitivity does not match the bioluminescent peak (Fig. 1B) as it does in twilight- and dark-active fireflies. Some relevant behavioural observations with respect to mating are presented.