Pagina-afbeeldingen
PDF

“In the Bahamas and probably elsewhere the ideal breeding-places for Culicoides furens are areas of waterlogged sand mixed with humus, not subject to actual flooding by any except unusually high tides, and more or less covered with a growth of mangroves. But even in such localities the sand-flies by no means breed evenly over the whole extent. A typical sand-fly swamp or “swash,” as it is called in the Bahamas, may be described as follows from a New Providence example: the sandy, or in places rocky, beach is backed closely by a sea-dune, often of considerable width and clothed with sea-oats (Uniola), coco-plum (Chrysobalamus Icaco) and low scrub. At some distance inland is a line of rock outcrops. Between these two ridges lies the swamp, into which extend the branches of a narrow arm of the sea, a creek in the original sense of the word. The margin of the swamp is everywhere clearly defined by distinct zones of vegetation. The lower portion, about the arms of the creek, is covered almost uniformly with common stilt mangroves (Rhizophora mangle). The upper portions and the margins are clothed with almost pure stands of low black mangrove (Avicemnia mitida). While the muddy sand between the Rhizophora bushes is invariably bare, that among the Avicemnia shrubs is often covered, though not densely, with the low reddish herbaceous plant, Salicornia perennis. On the extreme edge of the swamp, at the foot of the sea-dune and of the landward rock outcrop, is a thin line of other vege

tation, chiefly white mangrove (Laguncularia racemosa) and buttonwood (Conocarpus erecta) with denser beds of Salicornia and of the much greener. sampire (Philozerus vermicularis). Occasional patches of the salt-marsh grass, Sporobolus virginicus, also occur here. The distribution of these different vegetation zones depends upon distance from tidal influence. In the upper part of the swamp are frequent and extensive patches of bare soil. The soil of the whole area is permanently water-logged, while that in the immediate vicinity of the creek is flooded by every tide. The proportion of humus in the sand decreases as one approaches the mouth of the creek, where the sand is pure and almost white. “In the swamp thus briefly characterised, sand-flies (C. furens) breed in greatest abundance about the meeting-place of the common mangrove (Rhizophora) and the black mangrove (Avicennia) patches, and to a greater extent in the shade of the former than of the latter. They breed also, right up to the edge of the swamp, in the shade of white mangroves (Laguncularia), of sampire (Philocerus) of the grass, Sporobolus virginicus. “I was able to find none in precisely similar soil in the shade of Salicornia, nor in the bare patches. Neither does the sand-fly breed in the lower part of the common mangrove zone, where every tide covers the surface with several inches of water. To sum up, we may state that for breeding in numbers sand-flies (Culicoides furens) require (a) sand with a proportion of humus, permanently waterlogged with salt or brackish water, but not flooded, and (b) shade. It would be presumptuous to assert that odd sand-flies do not breed where some or even all of these conditions are lacking, but we are concerned here with main sources of infestation.” Painter (1927) reared C. furens from sand and mud near a tidal canal in Honduras. Carpenter (1951), Woke (1954), and Blanton et al. (1955) reported C. furens as a severe pest in Panama, breeding in the Farfan Swamp near Fort Kobbe, C.Z. They devised a system of tidal gates to keep the swamp flooded with fresh water from rainfall. Control was good until the gates deteriorated. Breeland (1960) reared this species in Panama from numerous collections from a wide variety of saltwater habitats and found it to be most abundant in mangrove swamps or marshes that were only partially shaded. The densest populations were found in supersaturated muck of tide ditches with no standing water and partial to full exposure to sunlight. This species was virtually absent in densely shaded mangrove Swamps. Williams (1964) reared C. furens in Trinidad not only from tidal and brackish habitats but also from the margin of a fresh-water stream miles from the seacoast. Linley and Kettle (1964) described the larva and pupa of C. furens, taken at Greenwood, east of Montego Bay, Jamaica. The breeding site was the shaded banks of two

[ocr errors]

ponds, situated close to the sea, which contained considerable sea water even though they were not connected directly to the sea. Williams (1962), working on Saint John, compared emergence trap catches from ordinary tidal mangrove swamps (Type I) with those from vegetated margins of brackish ponds receiving some water by seepage from the sea, but with higher levels from periods of heavy rainfall (Type II). Type I habitats produced a nearly constant, moderate emergence of adults, whereas type II habitats produced larger numbers beginning with the flooding of such ponds by rainfall and increasing until about a week after the mud was exposed by drying of the ponds. Linley (1966a) and Davies (1967) trapped C. furens in Jamaica in the Bogue Swamps east of Montego Bay in emergence cages along transects crossing various vegetation zones and tide levels. They generally found C. furens breeding in those parts of the swamp occupied by white or black mangroves (Laguncularia and Avicennia) at a slightly higher level (0.2 foot) than C. barbosai. Its emergence was hardly affected by general water levels, but unlike that of C. barbosai, the emergence of C. furens was greatly inhibited by high amplitude tides. For this reason the abundance of C. furens is unlikely to show much seasonal variation in Jamaica, but it is more abundant on a biweekly cycle during neap tides than during spring tides. Using emergence traps, Linley et al. (1970a) compared the seasonal emergence of C. furens in Florida from three habitat types—tidal ditches, brackish pools, and impoundments. Compared with the other two habitats, impoundments produced relatively few adults early in the year (March to June), but thereafter the rate of emergence in impoundments increased and during the cold months (September to March) exceeded that in the other two habitats. Linley (1968, 1969) described techniques for colonizing C. furens in Florida and included notes on behavior under laboratory conditions. Earlier he (1966a) reported on the behavior, habitat preferences, and food preferences of larvae collected in Jamaica and reared in the laboratory. In alternate periods the larvae exhibited two types of activity— (1) burrowing through the soil, presumably foraging for food, and (2) inactively lying at the soil surface to secure a better supply of oxygen. Just prior to pupation the larvae migrate some distance to drier soil

where contact with air can be made

more easily by the pupa. Biting Habits.--Kettle (1969b) found biting activity of C. furens in Jamaica to be crepuscular and nocturnal with a peak at dawn and irregular outbursts through the night. He (1969c) found that moderately high windspeed (above 3 m.p.h.) decreased the biting rate. Kettle and Linley (1969b) found that this species preferred to bite the legs rather than the arms of humans. This species is rather exceptional among Culicoides species in its habit

of freely entering houses and other buildings in search of a blood meal (Myers, 1935; Adamson, 1939; Porter, 1959). Wire screens at windows and doors are only partially effective in keeping them out, but spraying or painting the screens with kerosene to which suitable insecticide has been added is an effective repellent. Flight Range.—Williams (1962) found on Saint John in the Virgin Islands that adults of C. furens may be carried by prevailing winds for more than 4 miles over mountains 1,200 feet high. Breeland and Smith (1962) reported that C. furens in Panama was carried downwind a distance of about 2 miles. It seems likely that windborne C. furens may disperse from 3 to 4 miles from their breeding places, whereas upwind dispersal may be limited to several hundred yards. The reliability of prevailing winds or trade winds may be an important factor in planning control measures for this species (Linley and Davies, 1971).

Culicoides guadeloupensis Floch and Abonnenc

(Fig. 6)

Culicoides guadeloupensis Floch and Abonnenc, 1950, p. 2 (female; Guadeloupe I.; fig. wing, palpus, head, eyes, legs, spermatheca, pharynx).

Female.—Wing length 1.17 mm.

Head: Eyes with short interfacetal hairs. Antenna with five distal segments elongate, 11 longer than 9 and 10 combined; AR 1.65. Palpal segments with lengths in proportion of 19–52–57–24–33; third segment stout, with a large irregular shallow pit on distal portion; PR 1.4. Thorax: No data given. Wing: Wing pattern similar to that of C. trilineatus Fox; cell R5 with a single, oblique, poststigmatic pale spot and a transverse pale spot in distal portion; cell M1 with two pale spots; cell M2 with a pale spot behind medial fork, one in front of mediocubital fork, and one in distal portion of cell at wing margin; a small pale spot in cell M4; anal cell with a single pale spot in distal portion; vein M1 narrowly pale bordered on distal half. Macrotrichia abundant over entire wing; CR 0.67. Abdomen: One spermatheca present, subspherical, with a moderately long, slender neck; measuring 0.064 by 0.055 mm. Male Genitalia.-Male unknown. Distribution.—Guadeloupe (fig. 6). Type.-Known only from the holotype female, collected St.Claude, Guadeloupe, 1944–5, R. Chassignet (slide No. 1944, in coll. Inst. Pasteur de la Guyane, Cayenne). West Indian Records.-None. Discussion.—The previous description was taken from Floch and Abonnenc (1950). The wing pattern of C. guadeloupensis is practically indistinguishable from that of C. trilineatus, but the hairy eyes, the presence of only one spermatheca, and the markedly elongate distal antennal segments provide means for readily distinguishing C. guadelowpensis. Larval Habitat.—Unknown. Biting Habits.-Unknown.

Culicoides heliconiae Fox and Hoffman

(Figs. 3 and 18)

Culicoides heliconiae Fox and Hoffman, 1944, p. 108 (female; Venezuela; fig. wing).-Fox, 1948, p. 22 (male, female; fig. palpus, aedeagus, parameres)Wirth and Blanton, 1956e, p. 95 (redescribed; synonym: rozeboomi; illus.).-Wirth and Blanton, 1959, p. 274 (redescribed; Panama records; illus.):-Williams, 1964, p. 463 (Trinidad; larval habitats).-Wirth and Blanton, 1968, p. 205 (redescribed; illus.)-Wirth et al., 1968, p. 132 (Panama; reared from Heliconia).

Culicoides rozeboomi Barbosa, 1947, p. 26 (male, female; Trinidad; illus.).

Female.—Wing length 1.66 mm.

Head: Eyes contiguous, bare. Antenna (fig. 18, a) with lengths of flagellar segments in proportion of 60 — 50 — 50 — 50 — 50 — 50 — 50 — 50 — 65–66–80–83–108; AR 1.06; sensory pattern 3,11–15. Palpal segments (fig. 18, f) with lengths in proportion of 20–120–140–60–56; PR 3.6; third segment spindle shaped, with sensilla scattered on surface. Proboscis long, P/H ratio 1.33; mandible with 23 teeth.

Thorax: Blackish; mesonotum (fig. 18, c) with large median area and other smaller areas dark pruinose gray, lateral margins and a sublateral pair of short bands velvety black; humeri whitish. Legs blackish; midknee narrowly pale on each side of joint; fore femur with subapical, fore tibia with subbasal, and hind tibia with basal and apical, narrow pale rings; tibial comb (fig. 18, d) with six spines, second from spur longest.

Wing (fig. 18, b): Pattern as figured; 2RC with apex included in a pale spot; base of cell M4 dark where it borders bases of veins M3 +4 and Cu1; pale spot present in cell R5 anterior to base of vein M1; apices of veins M1, M2, M3+4, and

Cu1 with pale spot at wing margin. Macrotrichia sparse on distal half of wing and extending nearly to base of anal cell; CR 0.71. Halter pale. Abdomen: Blackish, cerci yellowish. Spermathecae (fig. 18, e) two plus rudimentary third and Sclero

FIGURE 18–Culicoides heliconiae: a, Female antenna; b, female wing; c, thoracic pattern; d, tibial comb; e, spermathecae; f, female palpus; g, male parameres; h, male genitalia, parameres removed.

[graphic]
« VorigeDoorgaan »