AMPHIBIOUS COCKROACHES
Audreia bromeliadarum
Panama.—These insects when disturbed would dive into the water that had collected in the base of the bromeliad; they would disappear beneath the surface and remain submerged for some considerable time (Caudell, 1914).
Dryadoblatta scotti
Trinidad.—This species was taken from the leaf bases of Tillandsia sp. at 3,100 feet; water had collected between the leaves and the insect was presumed to be more or less amphibious (Scott, 1912). Subaquatic in the bromeliad Glomeropitcairnia erectiflora: "This large and handsome species [D. scotti] is very common in the larger, water-filled, epiphytic bromeliads of the rain forest. Within these plants it is usually to be found, often in considerable numbers, just above the surface of the water or partly immersed in it. The cockroaches will descend rapidly into the water when alarmed and probably obtain their nourishment from the accumulated organic matter in the water. Floating material is probably taken and it seems less likely that they feed below the surface. They appear to be ovoviviparous." (Princis and Kevan, 1955.)
Epilampra abdomen-nigrum
Puerto Rico.—Abundant in wet "malojillo" meadows. The nymphs swim easily and remain under water for long periods, as do the adults (Seín, 1923; Wolcott, 1950).
Panama.—A swimming nymph, captured in a dipper with mosquito larvae in a lagoon of the Rio Chilibre, was kept under observations in an aquarium. If disturbed, the insect dived into the water from floating vegetation and swam rapidly below the surface for a minute or two. Finally becoming quiescent, the cockroach would then cling to submerged roots; twice it remained still for 15 minutes before climbing to the surface, where it remained for five or more minutes before emerging completely (Crowell, 1946).
Epilampra annandalei
Lower Burma.—One male and three nymphs were collected in the Dawna Hills by Annandale who made the following observations: "The wingless specimens were under stones in a jungle stream and behaved just as the one I obtained in Chota, Nagpur, did [Annandale, 1906]. The winged specimen was under a stone at the edge of the stream, but swam readily. It did not seem so much at home in the water, however, and apparently could not, owing to the wings, raise the tip of its abdomen above the surface." (Shelford, 1909a.)
Epilampra sp.
Siamese Malay States.—Wingless females rested on floating logs from which they would dive into the water upon the least disturbance; they remained under water for several minutes, then surfaced beneath the shelter of the log. In the jungle all females were taken either in the water or among matted roots on the sides of the stream. Winged males were seen rising from the surface of the water (Annandale, 1900).
Sarawak.—All specimens were immature; they swam and dived well, but were soon drowned if prevented from rising to the surface to breathe. "When at rest the body of the cockroach is almost entirely submerged, the tip of the abdomen alone projecting above the surface of the water; the abdomen moves gently up and down and every 30-40 seconds a bubble of air issues from the prothoracic spiracle on each side." (Shelford, 1901, 1916.)
India.—A nymphal female, found in a jungle stream at Chota Nagpur, could swim with belly or back upward. When held under water it drowned in a few minutes. The tip of the abdomen was held out of water (Annandale, 1906).
Shelford (1907) has suggested that the immature stages of terrestrial species of Epilampra may well be amphibious. This is an area that could profit by more field observations.
Opisthoplatia maculata
Formosa.—Invariably found under or between rocks near mountain streams. The wingless adult and the nymph have similar habits. Normally the cockroach lives on land, and when it goes into the water it returns to land within a few minutes. This cockroach rarely swims, but when it does, it maintains its body in a horizontal position just below the surface of the water. Ordinarily, it walks on the river bottom or on water-covered rocks. This insect feeds on decayed leaves and, according to Shikano, it will eat human feces. (Takahashi, 1926.)
This species has a large number of long hydrophobic hairs on the ventral sides of the thorax and anterior abdominal segments. When the insect submerges, air is trapped in these hairs. The thoracic and one pair of abdominal spiracles open into the bubble of trapped air. However, the insect apparently does not use this plastron of air to replenish its tracheal air supply, but, like Rhicnoda natatrix (see below), it inspires air while at the surface through its posterior abdominal spiracles and expires air into the bubble under the thorax. While the insect is submerged, the air bubble increases in volume until part of it breaks away and floats to the surface. (Takahashi, 1926.)
Opisthoplatia orientalis
Formosa.—Lives on or in swampy ground (Takahashi, 1924).
Rhicnoda natatrix
Sarawak.—Immature cockroaches were found in sodden leaves at the edge of a pool, where they rested for hours at a time. Generally the fore part of the body was in the water but the tip of the abdomen was always in air. When disturbed the insects dived into the water and hid under sticks and stones on the bottom. Air is inspired through the posterior abdominal spiracles, when they projected above the water surface, and expired through the thoracic spiracles. In experiments in which the insects' abdomens were held immersed in water, with the thorax exposed, the insects died in 6 to 12 hours or less. (Shelford, 1907.)
Stictolampra buqueti concinula
Westsumba.—Found under moist fallen leaves on gravelly shore of Melolo River. The nymphs distinguished themselves through their amphibious mode of life and were often good swimmers (Princis, 1957a).
Unidentified epilamprines
Brazil.—These cockroaches were found under stones at the side of a rocky stream at Ouro Preto. When disturbed they ran down under the surface of the water and hid under stones at the bottom. When thrown on the water surface, they were helpless, and to get beneath the water surface they had to walk down some object. When they had penetrated the surface film they could swim freely. Specimens kept in jars lived several days with only a portion of their abdomens exposed to the air. (Bristowe, 1925.)