Wirth, W.W.

Proceedings of the Hawaiian Entomological Society

ScholarSpace at University of Hawai'i at Manoa

141Ephydra gracilis Packard, a recent Immigrant Fly in Hawaii(Diptera: Ephydridae)1By WILLIS W. WIRTHP. A. Sanitarian (R), U. S. Public Health Service(Presented at the meeting of September 9, 1946)The first recorded occurrence of Ephydra gracilis Packard inthe Hawaiian Islands appears to be a specimen found in a light trapat Hickam Field in April 1946. A month later a second specimenwas taken in a light trap operated on Sand Island opposite Honolulu. In April a lookout was begun for breeding places while onroutine mosquito surveys on Oahu, but the habitat was not discovered until July 23.The flies were found to be breeding by the millions in salt-waterponds opposite the Moanalua Gardens, the water in these pondshaving become increasingly saline as dredging operations hadclosed the inlet from Keehi Lagoon. These flies skate around onthe water surface, congregating in dense masses near the shore,and fly up a few inches when disturbed to alight quickly on thewater again a foot or two away. They were seen to enclose themselves in a bubble of air which was captured under their wings,and to crawl by projecting sticks or stones to the bottom a fewinches below where their long straight tarsal claws (a genericcharacter) served well to anchor them as they crawled around,presumably ovipositing. This habit previously has been noted forB. hians Say in Great Salt Lake, Utah, but not for gracilis. Thelarvae and pupae were found in the dense algal masses in the waterand in the upper layers of the algae-covered bottom ooze.Essig (1926) briefly summarized the knowledge of gracilis existing at that time: Ephydra gracilis Packard is 2.3 to 3.5 mm.long, opaque gray, paler beneath and with a slight green tinge above,and bright green legs marked with yellow. The larvae are somewhat transparent white 10.6 mm. long, the anal tube which has abasal and apical pair of forks, is from the base to the terminal fork4.9 mm. long, each of the prongs of the terminal fork 1.6 mm., andeach basal fork 2 mm. in length. They have 8 pairs of long prolegs.The larvae live suspended everywhere in the open water of GreatSalt Lake and Salton sea, in salt water in San Francisco and adjacent to the Pacific Ocean at Laguna Beach, California. The fly was1 From the U. S. Quarantine Station, Honolulu, T. H.Proc. Hawn. Ent. Soc, Vol. XIII, No. 1, May, 1947.142introduced from Great Salt Lake into San Francisco Bay by railroad trains after the building of the cut-off at the lake; J. M. Aid-rich, Psyche, 25: 30, 1918."Aldrich (1912) had previously given a description of gracilis,adult, larva, and puparium, with biological notes, in a review of thebiologies of the western U. S. species of the genus Ephydra. Therelated species, hians, was often so abundant in western salt lakesthat windrows of puparia several feet deep were driven on thebeaches by storms; these when collected and prepared by the Indians were often used as food and given the name "Koo-chah-bie."More recent collections (August 26, 1946) at Iroquois Pointnear Pearl Harbor on Oahu showed gracilis to be quite abundantthere in salt marsh pools in which the water had evaporated almostto the saturation point of the contained salt. However, in pools inwhich salt crystallization had actually occurred gracilis larvae werekilled, but an undetermined syrphid fly larva (probably Lathyroph-thalmus aeneus) and larvae of a psychodid fly apparently were stillthriving.It is believed, in view of the habits of Ephydra gracilis and thecircumstances surrounding its first discovered occurrence in theHawaiian Islands, that the introduction of this species can be moredefinitely attributed to aircraft transport than can any other of thenumerous recently discovered insect immigrants. The close proximity of favorable breeding habitats at California seaplane bases,the large numbers of adults produced at times, their habit ofswarming into moving vehicles (where they are a pest, as in trainscrossing Great Salt Lake), and finally the proximity of receptivehabitats near the Oahu seaplane bases, together develop conditionsfavorable for insect "transplantation."The writer is indebted to Dr. Curtis W. Sabrosky of the U. S.National Museum for confirming the determination of theHawaiian specimens as Ephydra gracilis.REFERENCESAldrich, J. M.1912. "The biology of some western species of the dipterous genusBphydra." Jour. N. Y. Ent. Soc, 20: 77-99.Essig, E. O.1926. "Insects of Western North America," New York. p. 608.

Ephydra gracilis Packard, a recent Immigrant Fly in Hawaii (Diptera: Ephydridae)

http://scholarspace.manoa.hawaii.edu/bitstream/10125/16167/1/PHES13_141-142.pdf

Ephydra gracilis Packard, a recent Immigrant Fly in Hawaii (Diptera: Ephydridae)

Abstract

Similar works

Full text

Available Versions

ScholarSpace at University of Hawai'i at Manoa