Skulduggery in the insect world

Press, Volume CXIV, Issue 33433, 15 January 1974, Page 16

Skulduggery in the insect world

' By

WALTER SULLIVAN)

In firefly mating, skulduggery, rather than fair play, seems to be the rule, according to a study done in the highlands of New Guinea. According to a report of the study in a recent issue of the British journal “Nature,” it appears that an interloping male, by picking up the light-flashing rhythm of another male at the height of the latter’s courtship, can trick the female into switching partners. This was observed by Dr James E. Lloyd, of the University of Florida, in Gainesville, in seeking an explanation for the synchronous flashing of fireflies that has puzzled naturalists for centuries. In South-East Asia and Melanesia, fireflies perched en masse in a tree are sometimes seen flashing in highly precise unison. “FIERY CLOUD” After a voyage downriver from Bangkok in 1680 the Dutch physician Engelbert Waempfer told how these flies settle on a tree, “like a fiery cloud.” “A whole swarm of these insects,” he wrote, “having taken possession of one tree, and spread themselves over its branches, sometimes hide their light all at once, and a moment after make it appear again with the utmost regularity and exactness.” Researchers have asked: Who is the maestro who

Iconducts this extraordinary i “orchestra?” Dr John Buck, of the United States National Institute of Arthritis and ’Metabolic Diseases in Maryland, has proposed that something akin to the . human “sense of rhythm” is at work, like an audience that begins to clap in uni|son. However. Dr Lloyd, after studying recordings that he ’made on a visit to the south-west Pacific in 1969, has come to a different conclusion. He went on an expedition aboard the ship Alpha Helix of the Scripps Institution of Oceanography in La Jolla, (California. He found that small groups of males, of the igenus Pteroptyx, characteristically flashed in unison when gathered on a branch or bush. However, it was only rarely, he said, that an entire tree flashed in unison.

ATTRACTS FEMALES Dr Lloyd believes synchronous flashings of a small group helps attract a passing female, but that a whole treefull in unison has little value for the individual fly (they are actually members of the beetle family). Hence, he believes fulltree flashing occurs only when there is “contagion” of the rhythm from one group of synchronously flashing males to groups in other parts of the same tree. It had been suggested that synchronous flashing in an entire tree evolved to enable fireflies of the opposite sex to find one another in dense vegetation. Dr Lloyd however, doubts this. The flashing patterns of fireflies serve not only the courtship ritual but, like bird songs and plumage, also • enable those of one species to find mates of the same species in an environment where there may be scores of other firefly varieties. This is true in North America as well as New Guinea, where Dr Lloyd obtained photo-electric records of at least 20 species.

In one of them, a form of. Pteroptyx, the female char-’ acteristically flew over branches laden with males) announcing their sex with a characteristic flicker. The: females emitted a bright, steady glow, whereas the) males periodically flickered, at about 12 flashes a second, , This was often done ini unison and when a female “lamp” passed close over-1 [head. the males changed to a ; “response” flicker that was [much more irregular. Sometimes a female would, fly the entire length of a .hedge crowded with males,) [her position over the hedgei being evident by the re-j sponse flickering directly) below her. When a female landed near a male, a “dialogue” between them ensued until J the female, as part of the | ritual, took off with the ■ male in pursuit. At this I point many other males ’sometimes joined the chase, I but the female eventually landed and, apparently, did so with her original “beau.” It may be, Dr Lloyd says, 1 that the response flicker of each male has a “personality” enabling the female to recognise him. In some species, flying males are attracted to females that respond to, or “echo” their own flashes. Dr Lloyd, standing in the sparkling darkness of the highland wilderness, found that by flashing his penlight in response to male flashes, he was able to entice males from 50 to 100 ft away. They flew to within a few inches of his light, he

said, then sensed deception and departed. — (Copyright, ' “New York Times’’ news i service). 1