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Biomedical subjects

J R Linley

Publications and source records attributed to J R Linley.

At least 19 recordsLinked to original sources
PubMed1992

Effects of ultra-low volume and thermal fog malathion, Scourge and naled applied against caged adult Culicoides furens and Culex quinquefasciatus in open and vegetated terrain.

The adulticidal effect of ULV and thermal fog malathion, Scourge and naled was tested at 2x label dosage (1.42, 0.22, 0.39 oz/acre, respectively) against caged Culicoides furens and Culex quinquefasciatus in open and vegetated (orange grove) terrain. Cages were at 122 cm elevation and positioned at 15.2, 45.7, 76.2, 106.7, 137.2 and 167.6 m from the line of insecticide release. Ultra-low volume applications of all 3 insecticides were markedly more effective than thermal fog under all conditions, especially in vegetated terrain. Of the 3 insecticides, malathion performed the poorest, especially against Cx. quinquefasciatus (in which there was some resistance) and particularly when applied as thermal fog. Scourge and naled were about equally effective. The best adulticide against C. furens was naled, which was clearly superior applied as ULV. It yielded 75% mortality out to 283 m in the open, and to 38 m in the presence of dense vegetation.

Aerosols↗
PubMed1991

Fine structure of the eggs of Haemagogus equinus and Hg. janthinomys (Diptera: Culicidae).

The eggs of Haemagogus equinus Theobald and Hg. janthinomys Dyar, the first of this genus to be examined with a scanning electron microscope, are described from material collected in Trinidad, West Indies. All surfaces of the eggs are described, including both dorsal and ventral surfaces at the anterior and posterior ends as well as the micropyle and associated apparatus. The dorsal surface, normally attached to the substrate, consists of a dense, hairlike mat of filaments formed from numerous, greatly elongated outer chorionic tubercles. These filaments possibly serve to improve anchorage of the egg as a protection against flushing by rain water or physical removal by predators. The outer chorionic cells on the ventral (upper) surfaces are extremely similar to those of two species of the subgenus Finlaya of Aedes, Ae. albolateralis (Theobald) and Ae. melanopterus (Giles), both collected in Taiwan.

Animals↗
PubMed1990

Fine structure of the egg of Trichoprosopon digitatum (Diptera: Culicidae) and its relationship to egg raft formation.

Eggs of Trichoprosopon digitatum (Rondani) occur in rafts; the anterior poles are submerged, and the posterior two-thirds float above the water surface. Each egg is approximately 1,060 microns long and 270 microns wide. The hydrophilic end is more curved dorsally than ventrally and is covered with flattened, anteriorly pointed, scalelike tubercles except for a small area around the micropyle. The hydrophobic portion is clad in a layer of closely arrayed, small, round tubercles among which are positioned much larger, flattened, anteriorly directed tubercles with deeply fissured surfaces. At three positions equidistant around the periphery of the egg, narrow, tongue-shaped extensions (the embrasures) from the anterior hydrophilic region project posteriorly into the hydrophobic region. Along these embrasures, progressing posteriorly, the tubercles change in form from flattened and bladelike to finely tapered, then, at the extension's posterior two-thirds, to long filaments with well-developed terminal hooks. Eggs in rafts are maintained in polygonal rosettes by the interlocking of these filaments and hooks and the surface tension of menisci between contiguous embrasures.

Animals↗
PubMed1989

Egg of Aedes (Gymnometopa) mediovittatus (Diptera: Culicidae).

The egg of Aedes mediovittatus (Coquillett) is described from scanning electron micrographs. The egg is black, slightly tapered toward the posterior pole, and is approximately 771 microns long and up to 175 microns wide. On the entire egg surface there are about 970 polygonal outer chorionic cells, each bounded by a raised outer chorionic reticulum which forms a wall around each cell. Incorporated into the inner surface of this wall are 13-18 relatively small, poorly defined and variably shaped tubercles. In the center of each cell there is a large, buttonlike, more or less round tubercle with a pitted upper surface. Over most of the egg surface, the walls of this tubercle are connected by spokelike bridges of variable diameter to the cell floor or reticulum wall. The structure of the outer chorionic cells is somewhat modified in areas approaching the anterior and posterior poles.

Aedes↗
PubMed1989

Scanning electron microscopy of the egg of Aedes (Protomacleaya) triseriatus (Diptera: Culicidae).

The egg of Aedes triseriatus (Say) is described with the aid of scanning electron micrographs. The egg is dull black, very broadly cigar shaped, and slightly tapered posteriorly. The length is about 681 microns and the width about 202 microns. On the ventral surface, the irregularly pentagonal or hexagonal outer chorionic cells are about as long as wide and are bounded by the greatly elevated walls of the chorionic reticulum. Each cell has usually one (occasionally two or three) large tubercles set in the cell corners, abutted against the reticulum wall. On the dorsal surface, the chorionic cells are different in structure, each filled by a large, smooth domed tubercle. The micropylar collar is continuous (without gaps), and the micropylar disk is especially clearly defined and has a raised outer margin.

Aedes↗
PubMed1989

Comparative fine structure of the eggs of Aedes albopictus, Ae. aegypti, and Ae. bahamensis (Diptera: Culicidae).

Complete descriptions, including details of the micropylar apparatus and outer chorion at the anterior and posterior poles and on the dorsal surface, are given for the eggs of Aedes (Stegomyia) albopictus Skuse and Ae. (S.) aegypti (L.). The egg of Ae. (Howardina) bahamensis Berlin, the first of this subgenus to be examined with the electron microscope, is described for the first time. Certain characters may be useful for differentiating eggs of these three species under a stereomicroscope. The substantially greater egg length in Ae. bahamensis alone separates it from the other two species, at least in the laboratory populations studied. The micropylar collar in Ae. aegypti clearly differentiates it from the other two. Further examination of mixed groups of eggs is needed to determine whether fine structural differences in the outer chorion can be correlated with consistent differences in the stereomicroscopic image.

Aedes↗
PubMed1989

Laboratory tests of the effects of p-cresol and 4-methylcyclohexanol on oviposition by three species of Toxorhynchites mosquitoes.

Laboratory experiments tested the effects of p-cresol or 4-methylcyclohexanol at concentrations of 1, 10 and 50 ppm, on oviposition by the mosquitoes Toxorhynchites brevipalpis Theobald, Tx. amboinensis (Doleschall) and Tx. splendens (Wiedemann). A 5 + 5 ppm mixture of the two chemicals was also tested. All three species laid significantly more eggs in cups containing p-cresol, whereas only Tx. brevipalpis and Tx. amboinensis responded similarly to 4-methylcycohexonol and to the mixture of both chemicals. Tx. brevipalpis was, to a relatively limited degree, the most responsive of the three species. Ancillary experiments indicated that the chemicals were acting as attractants, causing more females to fly to treated cups. No stimulant effects were detected either in terms of the proportion of females that initiated oviposition flight (after flying to the cups) or in terms of the number of looping flights executed prior to ejection of an egg.

Animals↗
PubMed1989

Egg cannibalism and carnivory among three species of Toxorhynchites.

In laboratory experiments, third and early fourth instar larvae of Toxorhynchites amboinensis, Tx. splendens and Tx. brevipalpis, previously starved 24 h, rapidly cannibalized eggs of their own species, or ate the eggs of other species present on the water surface in small containers. Toxorhynchites amboinensis and Tx. splendens larvae of either instar cannibalized eggs somewhat more rapidly than Tx. brevipalpis, probably because brevipalpis eggs distributed themselves around the edge of the container and were less accessible. When offered heterospecific eggs, fourth instar larvae of all three species ate them as efficiently as they cannibalized their own except that eggs of Tx. brevipalpis were eaten very slowly. Toxorhynchites amboinensis larvae were offered conspecific hatched eggs, and these also were consumed.

Animals↗
PubMed1988

Laboratory experiments on factors affecting oviposition site selection in Toxorhynchites amboinensis (Diptera: Culicidae), with a report on the occurrence of egg cannibalism.

Laboratory experiments tested the effects of water quality and the presence of conspecific and heterospecific immatures on oviposition by Toxorhynchites amboinensis (Doleschall). The females showed a highly significant preference for oak leaf infusion water over distilled water. When twenty starved third and fourth instar Tx.amboinensis larvae were present in the water, substantially fewer eggs were counted from pots containing these conspecifics, than from controls in which no larvae were present. Numbers of eggs from pots containing starved second instar larvae did not differ significantly from controls. Observations of larval behaviour while oviposition was occurring suggested that egg numbers were reduced in containers because of egg cannibalism with third and fourth instar larvae, and not because the larvae caused a deterrent effect. Subsequent experiments confirming the occurrence of substantial egg cannibalism by third and especially fourth instar larvae are described. As with larvae, the presence of Tx.amboinensis pupae in the water had little effect on oviposition. If placed in the water 24 h prior to test, pupae very slightly enhanced its attractiveness, but if introduced immediately before test there appeared to be a slight deterrent effect. With heterospecific larvae, twenty fourth instar Ae.aegypti larvae introduced into infusion water 24 h before test rendered the water slightly attractive, while water in which Ae.aegypti larvae had been reared for 48 h proved highly repellent.

Aedes↗
PubMed1988

Evaluation of ULV naled applied simultaneously against caged adult Aedes taeniorhynchus and Culicoides furens.

Two experiments were conducted to test application of ULV naled against adult Aedes taeniorhynchus and Culicoides furens exposed simultaneously in cages hung on poles at selected heights and distances from the spray source. ULV spray was released at 0.14 oz active ingredient/acre, droplet size 13.5 micron mmd. In both experiments, insecticide largely carried over the first poles. The greatest mortality occurred at the second pole position, 18.3 and 25.7 m, respectively, from the spray origin, and diminished progressively with increasing distance. Cages at the highest elevation (183 cm) showed the greatest mortality, while those near the ground (15 cm) were substantially less affected. Regression analysis showed that 70% control or better was attained up to a distance (beyond a line 10 m from the release point) of 23 m in the case of Ae. taeniorhynchus and 18 m in the case of C. furens. ULV naled, applied as described, was not particularly effective for control of Ae. taeniorhynchus and C. furens, and was poor for insects exposed in low vegetation.

Aedes↗
PubMed1987

Polycyclic aromatic compounds as phototoxic mosquito larvicides.

The phototoxicity of 2-acetylnaphthalene, 1-acetylnaphthalene, 1-naphthalenecarboxaldehyde, 9-xanthenone, 9-thioxanthenone, 9-methylanthracene, anthracene, alpha-terthienyl, pyrene and fluoranthene was tested with larvae of Aedes aegypti, Ae. taeniorhynchus and Culex quinquefasciatus. The larvae were exposed to the chemicals in the presence of sunlight for intervals from 1 to 6 hr and the corresponding LC50 values calculated. The LC50 values determined when the 6-hr exposure was followed by 18 hr in the dark range from over 10 ppm to below 0.001 ppm. Naphthalene derivatives were the least active while alpha-terthienyl, anthracene, 9-methylanthracene, pyrene and fluoranthene were the most phototoxic.

Animals↗
PubMed1987

Evaluation of naled applied as a thermal fog against Culicoides furens (Diptera: Ceratopogonidae).

Naled/diesel oil (1:99), applied as a thermal fog, was tested against the biting midge Culicoides furens. The insects were confined in small cages suspended at 4 heights on poles at progressively greater distances from the fog release point. In terms of population survival 24 hr after treatment, a parabolic equation accurately described the regression of percent survival on distance from the release point. If 10% survival is considered as the maximum acceptable, then the equation predicts adequate control up to 19.6 m (64.3 ft) from the fog release point.

Animals↗
PubMed1986

The effect of salinity on oviposition and egg hatching in Culicoides variipennis sonorensis (Diptera: Ceratopogonidae).

The preferences of Culicoides variipennis sonorensis females for oviposition on different salinities were tested in experiments using small wells in a 4 x 4 latin square array. The mean numbers of eggs deposited on wet surfaces on salinites of 0.0, 9.9, 19.0 and 34.0O/OO, were 1212, 659, 287, and 0, respectively. Within a higher range, salinites of 19.0, 23.0, 28.0 and 34.0O/OO yielded mean numbers laid of 110, 3, 6 and 0, respectively. The overall relationship could be reasonably well described by linear regression, implying, under experimental conditions, a decline of 458 eggs laid for every 10O/OO increase in salinity. Eggs laid directly onto salinities up to 19.0O/OO survived and hatched equally well; at 34O/OO, however, no eggs became tanned and none hatched. In contrast, when eggs were laid onto fresh water, then transferred to different salinities 24 hr later, they survived and hatched even at 34O/OO.

Animals↗