Signals with Glows, Flashes and Pheromones

Firefly communication is one of the more easily accessible wild animal behaviors to study. With simply a penlight and notebook, a careful observer may be able to:

1. distinguish several species by the flashing patterns of the males;
2. learn the flash codes of several species by imitating (with a penlight) the flash patterns of the flying males and noting the female responses;
3. attract males by imitating the female's response flash;
4. find predaceous fireflies that mimic the females of other species;
5. observe the aerial attacks by Photuris females by imitating the flying males of other species;
6. find Photuris species that use two or more distinctive patterns in their search for mates.

In this paper, Dr. Lloyd takes a broad view of communication in North American fireflies, outlining the three basic modes of communication found among them.
The (Daytime) Dark Fireflies
Some fireflies are non-luminescent. A number of these dark firefly species use pheromones (perfumes) for communication. The female emits the pheromone into the air and it wafts downwind in an invisible cloud called a plume. The male follows the plume upwind until he reaches the female.
Each species has its own unique pheromone and will attract a mate only of the same species.
The Glowworm Fireflies
The simplest form of light signaling known to occur is found in several western fireflies and three rare fireflies from Florida. Females of these fireflies are called glowworms. They often live in burrows but appear above ground at night, turning on their lamps to attract mates.
Most male glowworm fireflies do not have light organs as adults. Instead, the males have especially large eyes to search for the glow of the females. In a few of these species, the females may produce pheromones as well.
In some of the species, the males do have a light organ and emit a glow. Females will remain dark until they spot an illuminated male flying above. Only then will the female light up. Using their lamps for such a short time reduces their risk of being spotted by a predator.
The Lightningbug (flashing) Fireflies
Lightningbug fireflies control their lanterns with precision and illuminate them in short flashes. In the eastern half of the US, there are about 130 species of lightningbugs. Representative of this type is the Big Dipper, Photinus pyralis. The Big Dipper is active at twilight before the daylight fully disappears; its yellow flash stands out against the green of background foliage.
Male and female lightningbugs look very much alike. The most conspicuous difference is the size of their lantern. The male lantern occupies two full segments, while that of the female is much smaller, usually only a half-moon in the center of one segment. The males and females also differ in the size of their eyes—those of the males being much larger.
The males flash while in flight. When the female sees the male's flash, she waits a certain number of seconds—in the case of the Big Dipper it is 2 to 4 seconds—then responds with her flash. The delay interval is not constant, however; the timing of both male and female flashing varies with temperature.
That the flash rate changes with the temperature raises a question that to date remains unanswered. If their time-coded flashes are indeed temperature dependent, communication between the male and female would seem to be viable only if the temperature of the male and female were roughly the same. Yet the female is perched, expending little energy, while the muscle contractions necessary for male flight theoretically generate heat, suggesting that the male must be considerably warmer than the female. If this is true, then how do males and females maintain communication with each other when their own temperatures differ?

Species Counts of the Lampyriae Beetles of the United States. From the Fireflyer Companion, Vol. 1 No. 3.

State	Dark Fireflies	Glowworms	Lightningbugs	Total Number of Fireflies
Alabama	6 - 7	1	22 - 28	24 - 39
Alaska	1	0	0	1
Arizona	4 - 5	9	2 - 5	15 - 20
Arkansas	6 - 7	1	22 - 28	24 - 39
California	6 - 7	8	0	15 - 20
Colorado	4 - 5	1	2 - 5	4 - 11
Connecticut	6 - 7	0	22 - 28	24 - 39
Delaware	6 - 7	0	22 - 28	24 - 39
Florida	6 - 7	3	45	56
Georgia	8 - 9	3	43	56
Hawaii	0	0	0	0
Idaho	2	0	2 - 5	4 - 11
Illinois	6 - 7	2	22 - 28	24 - 39
Indiana	6 - 7	2	22 - 28	24 - 39
Iowa	6 - 7	0	11 - 20	24 - 39
Kansas	6 - 7	1	11 - 20	15 - 20
Kentucky	8 - 9	2	22 - 28	24 - 39
Louisiana	4 - 5	1	11 - 20	15 - 20
Maine	4 - 5	0	11 - 20	15 - 20
Maryland	6 - 7	2	29 - 31	24 - 39
Massachusetts	4 - 5	0	11 - 20	24 - 39
Michigan	6 - 7	1	11 - 20	24 - 39
Minnesota	6 - 7	0	11 - 20	15 - 20
Mississippi	4 - 5	1	22 - 28	24 - 39
Missouri	6 - 7	1	22 - 28	24 - 39
Montana	2	0	2 - 5	15 - 20
Nebraska	6 - 7	0	11 - 20	15 - 20
Nevada	1	2	0	4 - 11
New Hampshire	4 - 5	0	11 - 20	15 - 20
New Jersey	6 - 7	0	11 - 20	24 - 39
New Mexico	4 - 5	8	2 - 5	15 - 20
New York	6 - 7	0	22 - 28	24 - 39
North Carolina	8 - 9	2	29 - 31	42
North Dakota	4 - 5	0	11 - 20	15 - 20
Ohio	8 - 9	2	11 - 20	24 - 39
Oklahoma	6 - 7	1	11 - 20	24 - 39
Oregon	6 - 7	2	0	4 - 11
Pennsylvania	8 - 9	2	22 - 28	24 - 39
Rhode Island	6 - 7	0	22 - 28	24 - 39
South Carolina	8 - 9	2	39	50
South Dakota	4 - 5	0	11 - 20	15 - 20
Tennessee	10	2	22 - 28	24 - 39
Texas	10	3	22 - 28	24 - 39
Utah	2	2	2 - 5	4 - 11
Vermont	4 - 5	0	11 - 20	15 - 20
Virginia	6 - 7	2	22 - 28	24 - 39
Washington	4 - 5	2	0	4 - 11
West Virginia	6 - 7	2	11 - 20	24 - 39
Wisconsin	6 - 7	0	11 - 20	24 - 39
Wyoming	2	0	11 - 20	4 - 11

Species Counts of the Lampyriae Beetles of Canada. From paper (PDF) by J. McNamara.

Province/Territory	Dark Fireflies	Glowworms	Lightningbugs	Total Number of Fireflies
Alberta	1	1	1	3
British Columbia	6	2	1	9
Manitoba	3	0	9	12
New Brunswick	4	0	4	8
Newfoundland	1	0	1	2
Northwest Territories	1	0	2	3
Nova Scotia	3	1	6	10
Ontario	6	0	13	19
P.E.I.	0	0	1	1
Quebec	5	0	8	13
Saskatchewan	1	0	4	5