FIGURE 3 A graphic scene of firefly emissions, with alphanumeric coordinates to index text discussion. The diagram illustrates flash patterns, response flashes, a warning flash (3N), an attack flash (7E), illumination flashes, a flash pattern default (9D), some (probably?) meaningless flashes of "stressed" fireflies (6J, 7N, 9F), and a Photuris larval glow (8L-10L).

given location. In Fig. 3 several examples are illustrated. A male Photinus macdermotti flies from 2E to 7E, repeating his two-flash pattern every few seconds; a Photinus collustrans presents several of his low arcing flash patterns behind the fence 9F-12F; Photuris frontalis males fly low in the woods beyond the fence at 3E-7D; a Photinus pyralis repeats his J-stroked flash pattern diagonally across the view between 1F and 11K, and three or possibly four Photuris species cruise over the forest canopy where high-flying one-short-flash patterns are often difficult to identify without attracting the emitters to view them in the hand, but the crescendo flash at 3B-9A is that of Photuris lucicrescens. Low in the woods at the upper right (10E-12D) two glowing males of the glowworm firefly Phausis reticulata cruise low over the ground emitting their green light continuously.

In the signal system used by most North American lightningbugs, perched females flash responses to the flash patterns of males of their own species. The response signals of females are single flashes in most cases, emitted after a slight delay (<1 s) and, after a brief dialogue of flash patterns and responses, males reach and mount answering females. However, the female delay in the common Photinus pyralis is distinctive and varies between 2 and 4 s, depending upon temperature. A female Photinus pyralis is answering her male from a perch up a spike of grass near 12L.

After mating, males return to mate searching and females turn to ovipositing and/or hunting (Photuris); this explains why males nearly always greatly outnumber females during their mating-time window, although the sex ratio at egg laying and at adult eclosion is expected to be 1:1. The operational sex ratio is reversed in some species toward the end of the season. Under such circumstances males theoretically are expected to become the more discriminating (i.e., the choosier) of a courting pair. Individuals may receive information that influences their flashing and mating behavior from the number of other flash patterns they observe around them.

Among the dangers that flying, signaling males encounter in the dark are the predaceous firefly females of the genus Photuris. These versatile femmes fatales mimic the flash responses of females of other species, attract males, and eat them (Fig. 4; termed variously aggressive, Batesian-Wallacian,

FIGURE 4 A predatory female of the genus Photuris (Florida member of the Photur. versicolor complex) devouring a male Photinus tanytoxus she has attracted with false mating signals. When hunting females of this species are presented with simulated "hovering" male flash patterns they sometimes launch aerial attacks.

FIGURE 4 A predatory female of the genus Photuris (Florida member of the Photur. versicolor complex) devouring a male Photinus tanytoxus she has attracted with false mating signals. When hunting females of this species are presented with simulated "hovering" male flash patterns they sometimes launch aerial attacks.

or Peckhammian mimicry); they also launch aerial attacks on flying, flashing males, aiming at their luminescent emissions. In Fig. 3, the flash pattern of the Photinus macdermotti male is answered (6F) but he flies on, then is attacked in the air (7E) by the Photuris female. Such predators may be expected to have had a strong evolutionary impact on both the signal coding (countermeasure trickery) of prey species and the flight paths and bioluminescent signals of mate-seeking males. Predaceous females obtain the defensive steroidal pyrones called lucibufagens from some firefly prey, which they incorporate into their own and their eggs' defenses.

The hawking Photuris female (7E) flashes just as she reaches the male, and they fall glowing into the shrub; possibly illuminating her attack so she could seize him. Photuris females use what appear to be illumination flashes in other situations: as they approach the ground or vegetation for landing (2J—6L); as they climb vegetation and take flight, when their flashes gradually become less frequent, then stop altogether as the females disappear into the night (7L—6I); and as they walk around in tangles of vegetation on the ground (5M-6M, 9L), perhaps seeking oviposition sites. Other flashes of unlikely if any behavioral-ecological significance are those emitted by fireflies in spider webs (6J), water puddles (7N), and tangles of Spanish moss (9F).

Males of many Photuris species use two or more flash patterns during mate search. Several species in one species group use a flicker with modulations timed exactly like those in the flash pattern of Pyractomena angulata (similar to the flicker shown in Fig. 1F), in addition to their species' own identification flash pattern. For example, Photuris tremulans males usually emit a single short flash every 2 s (20°C; Fig. 3, 2C—3C), but occasionally several or all males in a local population will emit the described Py. angulata flicker pattern (except it is green, not amber). When a short-flashing Photuris tremulans male is answered with a short flash, he approaches the respondent (female or penlight), maintaining a dialogue, and lands near; but, when a flickering male is answered, he switches (defaults) to his short flash pattern and then approaches as described (11C—9D).

When males of a related Photuris species receive an answer to their Py. angulata flicker (supernumerary) pattern, they default to their species' identification pattern, which is a pulsed pattern like the one seen above the trees at 2B—4B, or a variation of it. This firefly demonstrates another twist in the use of supernumerary flash patterns that will be important for understanding bioluminescent communication. For a few minutes at the onset of evening activity all males begin with the pulsing pattern but soon some, then more and more of them use their Py. angulata flicker pattern, until in an hour or so a peak of 50 to 80% flickering is reached; then, the proportion of males using the flicker pattern gradually decreases across the midnight hour.

Contrasting behavior of Photuris lucicrescens may be helpful for understanding signals of other Photuris species. They also use two flash patterns, a short flash and a crescendo flash (5B-7B), but they apparently do not switch patterns

FIGURE 5 Male fireflies of two Photuris species flashing over an oldfield in Connecticut seeking mates. One species is responsible for nearly all of the patterns seen here.

(default) during approach, and a nocturnal changeover has not yet been recognized. There is much to be learned about the behavioral ecology of Photuris fireflies and, in particular, the sexual selection aspects of their bioluminescent signals (Fig. 5). Note that the supernumerary patterns of several Photuris species are copies of flash patterns of known prey of the males' own females. In other words, pattern-copying Photuris males use a signal that hunting conspecific females will answer. This suggests a possible evolutionary origin of these prey-mimicking mate search patterns. Without this information the behavioral ecologist cannot understand selection pressures that have influenced the evolution of the bioluminescent signals we see today.

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