4th-stage Larvae Research Articles

Inhibition of development of Ostertagia ostertagi--effect of temperature on the infective larval stage.

Populations of Ostertagia ostertagi established from fresh larvae and from larvae stored at 4 degrees C for up to 12 weeks contained about 10% inhibited early 4th-stage larvae. This value rose to 21% after 16 weeks, due to an increase in numbers of inhibited larvae while adult numbers remained unchanged. Storage at 15 degrees C had no effect. In the case of larvae stored at 4 degrees C for 8 weeks, increasing the larval dose to 90000 had no significant effect on the proportion of the dose which was inhibited. The response to low temperature storage was much weaker than in previously reported studies on British populations, which accords with our earlier conclusion that low temperature cannot be the effective stimulus for inhibition in Australia.

Inhibited development of Ostertagia ostertagi in relation to production systems for cattle.

On a coastal farm in New South Wales where beef and dairy cattle production was carried on side-by-side, separate pasture plots were contaminated with eggs of Ostertagia ostertagi by calves from each production system in autumn, winter or spring. Successive groups of parasite-free tracer calves grazed on the plots for 14 days at 4-week intervals and were then killed for worm counts 14 days after removal from pasture. On all plots, the proportion of inhibited early 4th-stage larvae in tracer calves reached a maximum in spring, and was consistently and very significantly higher in calves which grazed plots contaminated with O. ostertagi of beef cattle origin. Factors which may be responsible for this difference between beef and dairy cattle populations of O. ostertagi are discussed.

Nuclear polyhedrosis virus infection ofPseudoplusia includens [Lep.: Noctuidae] larvae: Effect on post larval stages and transmission

Treatment ofPseudoplusia includens (Walker) larvae in either the 4th, 5th or 6th stage with a nuclear polyhedrosis virus (NPV) did not affect the weight or sex ratio of surviving pupae. Pupal mortality was low but increased with the dosage of the NPV larvae had received. Also, mortality of pupae from larvae treated in the 5th or 6th stage was higher than from larvae treated in the 4th stage. Adult longevity was not affected by the virus. Fecundity and egg viability were reduced following most treatments of 6th stage larvae but not 4th or 5th stage larvae. Adults exposed to NPV at 3 dosages during the 6th larval stage were released in cages on soybean. Some of the progeny succumbed to NPV infection. Progeny mortality increased over a 7 week period of adult release, but did not differ significantly between treated and untreated groups by the end of the 7 week period.

Evaluation of Organophosphorus and Pyrethroid Insecticides for Control of the Pale Western Cutworm1

In comparative oral toxicity tests with 5th-stage larvae of Agrotis orthogonia Morrison, 8 pyrethroids were more toxic than 17 organophosphorus insecticides. Decamethrin was 10 × more toxic than endrin, whereas AC 222705 ((±)-Cyano[3-phenoxyphenyl]methyl(±)-4-[difluromethoxy]-α-[1-methylethyl] benzeneacetate) > cypermethrin > endrin = fenpropanate = permethrin > fenvalerate = FMC 26021 ([5-benzyl-3-furyl]methyl(+)trans-2,2-dimethyl-3-[2-methyl-1-propenyl][cyclopropanecarboxylate]). The organophosphorus insecticides, Bay 77049 (O,O-diethyl-O-[2-quinoxalinyl] phosphorothioate), monocrotophos, chlorpyrifos, and N 2596 (O-ethyl S-[P-chlorophenyl] ethyl phosphorodithioate) were equal in toxicity but were 3–4 × less toxic than endrin. The remaining insecticides were 5–30 × less toxic than endrin. As contact poisons, the pyrethroids were 4–156 × more toxic than endrin with decamethrin as the most toxic. Chlorpyrifos was equal to endrin but both were 2 and 8 × less toxic, respectively, as contact than as oral poisons whereas the pyrethroids except for AC 222705 and FMC 18739 were 2–3 × more toxic as contact poisons. In greenhouse tests, cypermethrin, fenvalerate, and permethrin at 0.07 kg/ha were as effective as endrin at 0.28 and chlorpyrifos at 0.56 kg/ha when applied to wheat plants or to bare soil. These pyrethroids at 0.28 kg/ha applied to bare soil gave significantly better control than endrin at 0.28 and chlorpyrifos at 0.56 kg/ha. Leptophos was as effective as chlorpyrifos when applied to wheat plants but was less effective when soil applied. Methamidophos was unsatisfactory at the rates tested.

Western Spruce Budworm Aerial Application with Sir 8514, 1979-1980

Abstract SIR 8514 0.25 WP was applied to a Douglas-fir stand by helicopter, at a dosage rate of 2 oz ai/acre, against 5th and 6th stage larvae of the western spruce budworm, in central Montana, July 2, 1979. The same insecticide was applied by helicopter to grand-fir against 4th and 5th stage larvae of western spruce budworm near Donnelly, Idaho, Jun 22, 1980, but at a dosage rate of 4 oz ai/acre. For both applications, SIR 8514 was mixed with water for a total volume of 1 gal/acre and applied with 8002 flat fan nozzle tips, at 45 mph, 50 ft above tree tops. Each year, tests were limited to a single dosage rate applied to three plots with 5 additional plots (1979), and 3 additional plots (1980), serving as checks. Spray plots were 50 acres in size and at 5500-6000 ft elevation in Montana and 5500-6200 ft elevation in Idaho. Each plot contained 15 sample trees. Populations were expressed as mean number of larvae/100 buds; population estimates were determined 24 hr prespray, and at 3 intervals postspray in Montana and 4 intervals postspray in Idaho.

Effects of a mammalian cholesterol biosynthesis inhibitor on adipocyte ultrastructure and metamorphosis in Rhodnius prolixus (Hemiptera).

A potent inhibitor of cholesterol biosynthesis in rodents [BMVA; 5-(4-biphenylyl)-3-methylvaleric acid] inhibits metamorphosis of 4th stage larvae of the blood-sucking bug Rhodnius prolixus.

Prediction of Pupation in Toxorhynchites brevipalpis (Diptera: Culicidae)1

Changes in pattern of the thoracic pigmentation in 4th-stage Toxorhynchites brevipalpis Theobald larvae are proposed as a reliable indicator for estimating of the age of 4th-stage larvae and the time of pupation. This method can be a useful tool in age segregation of field collected Toxorhynchites brevipalpis larvae as well as for segregation of larvae for uniform pupation in mass rearing of these predacious larvae for biological control purposes.

Development Time and Mortality of Dendroctonus frontalis1 in Relation to Changes in Tree Moisture and Xylem Water Potential 2

Development time and observed mortality of Dendroctonus frontalis Zimm. in relation to changes in host-tree condition were studied in east Texas during the summer of 1977. Four indices of host condition were monitored: bark, phloem, and xylem moisture and twig xylem water potential. Successful attack initiated predictable patterns of drying and rehydration in the phloem and xylem, and increasingly negative water potentials at the branch tips. These patterns were described mathematically and correlated to beetle development time. Eggs and 1st stage larvae were not affected by changes in phloem moisture in individual trees. However, development of 2nd- and 3rd-stage larvae was slowed when phloem moisture stayed above ca. 170% oven dry weight prior to those stages. Development of 2nd- and 3rd-stage larvae was also slowed in trees exhibiting large decreases in phloem moisture during those stages. Larval mortality was greater than mortality to other life stages. Concurrently, changes in phloem moisture were greatest when larvae were developing. Bark moisture remained at ca. 30% oven dry weight throughout beetle development. Development of 4th stage larvae and pupae was slower in trees with high average bark moisture during those stages.

A STEPWISE COMPUTER PROGRAM FOR ESTIMATING DEVELOPMENT TIME AND SURVIVAL OF AEDES VEXANS (DIPTERA: CULICIDAE) LARVAE AND PUPAE IN FIELD POPULATIONS IN SOUTHERN ALBERTA

AbstractGrowth and survival rates for larvae and pupae of Aedes vexans (Meigen) were measured in the laboratory at constant temperatures of 10°, 15°, 20°, 25°, and 30 °C. Growth rates in all stages increased with temperature except for 1st stage larvae which developed marginally faster at 25°C than at 30°C. The shortest stage at all temperatures was the 2nd, followed in most cases by the 3rd, 1st, and 4th larval stages, and then pupae; pupae and 4th stage larvae took markedly longer to develop at low temperatures. Average survival rate was about 99% every 3 h for larvae and 98% for pupae. At 10° and 15°C, 1st and 2nd stage larvae survived no better than later stages, but at the higher temperatures survival to the 3rd stage larva was better than 90% but decreased markedly in the 3rd and 4th stages. Overall survival was highest at 25°C. Mosquitoes reared at 10°C did not pupate, while those reared at 30 °C pupated but adults did not emerge.These laboratory data were used in a computer program whose output under field temperature regimes was compared with events in the field. The program works in 3 h time-steps. Rate of development varies with temperature and utilizes a modification of the algorithm of Stinner et al. (1975); the modification removes time as the independent variable in the development equation. Mortality rates are constant at 1% every 3 h for larvae and 2% for pupae. The program’s predictions for graduation from one stage to the next in the field population were all within about 13 h of the observed times and at the start of the pupal stage after 400 h, the output was running 13 h slow. The program appears to run slow at median temperatures below 10 °C and fast at median temperatures above 14°C. Events in the laboratory rearings are offered as possible explanations for these discrepancies. Predicted population size was close to that observed until the late 4th stage larva, from which point it deviated markedly. Pupal mortality in the field was much higher than in the laboratory.

Effect of Diethylcarbamazine Citrate on Fourth Stage and Adult Brugia Malayi in Cats *

Sixty-three experimental and 58 control cats were infected with Brugia malayi so that the developing and adult worms localized in the regional lymphatics of the hind legs. At 20 days after infection when Brugia were in the 4th larval stage, and at 8 weeks when worms were young adults, cats were divided into groups to test the efficacy of diethylcarbamazine citrate (DEC) at various dosage levels. At 100 mg total DEC/kg no 4th-stage larvae were seen in 5 cats compared with a mean of 20.4 living larvae in each of 5 controls. At this level of DEC, 2 of 5 cats had 1 and 2 adult worms while 4 of 4 controls had a mean of 23.2 living adult worms. At 50 and 25 mg/kg there was a substantial reduction of both 4th stage and adult worms when compared to controls. At 10 mg/kg, 4 of 6 cats had 4th-stage larvae but at a lower level (mean = 7.0) than in 6 controls (mean = 23.2). No reduction of either 4th-stage larvae or adult worms was seen at 1 mg/kg. This study establishes the efficacy of DEC against 4th-stage and adult Brugia malayi in cats, although considerably higher levels of the drug were required than the level previously determined to kill 3rd-stage larvae. It appears that the cat-B. malayi model will be an effective method to compare the efficacy of drugs against adult lymphatic-dwelling filariae.

NITROSCANATE* A NEW BROAD SPECTRUM ANTHELMINTIC AGAINST NEMATODES AND CESTODES OF DOGS AND CATS

SUMMARY: The efficiency of the broad spectrum anthelmintic nitroscanate against tapeworm and nematode infections of dogs was tested in artificially or naturally infected dogs. The safety of the compound was also evaluated in acute, subacute and chronic toxicity tests.At the recommended single dose rate of 50 mg/kg given to the dogs with food, nitroscanate was 98% efficient against Taenia hydatigena, T. ovis and T. pisiformis. The drug was highly efficient against Echinococcus granulosus only at the dose rate of 200 mg/kg given twice but total elimination of worms was not achieved. Natural infections of Dipylidium caninum, Ancylostoma spp and Uncinaria stenocephala were totally eliminated from all dogs at the dose rate of 25 mg/kg or higher.Nitroscanate was 97% efficient against adult Toxocara canis at a single dose of 50 mg/kg. When the dose was repeated 24 hours later total elimination of both mature worms and immature worms in puppies aged 2 weeks was achieved. The repeated dose of 100 mg/kg removed 98% of early immature worms from puppies aged 3 days. The drug was 100% efficient against adult Toxascaris leonina at a single dose of 50 mg/kg and 90.5% efficiency was achieved against early 4th stage larvae by two doses of 50 mg/kg. Nitroscanate was not efficient against Trichuris vulpis.The drug was efficient for the removal of Toxocara cati and Ancylostoma tubaeforme from cats.Nitroscanate caused no serious symptoms of toxicity at dose rates up to 10,000 mg/kg in single or repeated doses in young or older adult dogs. The drug was safely given to dogs during pregnancy, to young puppies and to cats. The regular use of nitroscanate as a broad spectrum anthelmintic for the prevention and control of parasitic infections of dogs is discussed.

Morphology of the Advanced-Stage Larva of Eustrongylides wenrichi Canavan 1929, Occurring Encapsulated in the Tissues of Amphiuma in Louisiana

Larval nematodes identified as Eustrongylides wenrichi Canavan 1929, from cysts in the tissues of Amphiuma means tridactylum Cuvier in Louisana were redescribed. The extent of differentiation of the sex organs was found to be greater than that of 3rd-stage Dioctophyma renale, or of the infective stage of Trichinella spiralis, and comparable with the late 4th-stage larva of secernentean (phasmid) nematodes.

Ultrastructural Changes Associated with Development of Pin Namatode, Graculacus sp., with Special Reference to Its Survival : Ecological significance of dormancy in plant parasitic nematodes. VIII.

The 4th stage larvae (L4s) of Gracilacus sp.2 prior to lethsargus withstand unfavorable conditions for a longer time than lethargic L4s and adults; for more than 42 months in soil kept in polythene bags and at least 80 days in water-saturated soil. For all thicknesses of cuticle, the ratio of the external cortical and basel layer of the quiescent L4s was ca. 10% and 55%, respectively, being the largest in all stages examined. With the development of L4s to adulthood, the permeability of cuticle increased. The intestinal cells of L4s were filled with lipid droplets, which decreased in amount and some of which changed into the age pigment granules in adults. In the course of the formation of adult cuticle, electron dence balls appeared in the lateral hypodermis of the lethargic L4s. Changes in survivability with development is discussed from an ultrastructural viewpoint.

Haemolymph levels of juvenile hormone, ecdysteroids and protein during the last two larval instars of Locusta migratoria

Abstract The radioimmunoassay of ecdysteroids and juvenile hormone has enabled us to relate hormone levels to haemolymph protein concentrations and weight increase during the 4th and 5th instar of the migratory locust. The two hormones are never present in high concentrations in the blood simultaneously. The levels of ecdysteroids are high on the 5th day during the 4th larval stage: they show a small peak on the 3rd day, and then a large peak on the 8th day during the 5th instar. JHI-immunoreactive substances are high during the first 4 days of the 4th instar, and during the first 5 hr during the 5th instar. Protein concentrations in the haemolymph begin to rise when ecdysteroid levels increase during stage 4, and immediately after the small peak (on day 3) in the 4th stage larva. The rise in protein levels is correlated with an increase in weight.

Factors involved in the relative anthelmintic tolerance of arrested 4th stage larvae of Ostertagia ostertagi.

Factors involved in the relative anthelmintic tolerance of arrested 4th stage larvae of Ostertagia ostertagi.

Induction of Sulphate Transport and Hormonal Control of Fluid Secretion by Malpighian Tubules of Larvae of the Mosquito Aedes Taeniorhynchus

ABSTRACT 4th stage larvae of A. taeniorhynchus reared in sulphate-enriched sea water drink the medium at the same rate that they do when reared in sulphate-free sea water. They absorb into the haemolymph most of the water and nearly all of the sulphate from the ingested fluid. Larvae are able to keep the concentration of sulphate in the haemolymph at levels well below that of the medium, even when this contains as much as 89 mm sulphate. The Malpighian tubules of larvae reared in sulphate-containing waters soon develop an ability to transport sulphate. The rate of sulphate transport induced varies directly with the sulphate content of the water in which they are reared. This ability is not retained into the adult stage. The rate of fluid secretion by isolated Malpighian tubules is increased by up to 20 times when they are exposed to saline containing 1·5 mm cyclic AMP or concentrations of 5-hydroxytryptamine higher than 10−6M. Tubules isolated from unfed insects into stimulant-free saline secrete fluid only slowly, but similarly treated tubules from feeding insects initially secrete fluid very much faster. Extracts of the brain and of the thoracic ganglia stimulate Malpighian tubules to secrete fluid at a high rate. The brain is about four times as rich a source of stimulant as is the chain of thoracic ganglia. Treatment of the surface of the structures in the head with K-rich saline leads to the release of a factor which stimulates fluid secretion by the Malpighian tubules. The results suggest that the Malpighian tubules in larvae of A. taeniorhynchus are under the control of a diuretic hormone which is elaborated in the brain and possibly also in the thoracic ganglia and which reaches high levels in the circulating haemolymph of feeding animals. The rate of sulphate transport by isolated Malpighian tubules is strongly affected by the rate of fluid secretion. This behaviour is compatible with a passive leak of transported sulphate from the lumen back into the haemolymph through the permeable wall of the tubule.

Effects of Parasitism by a Tachinid, Lixophaga diatraeae1 on Growth and Food Consumption of Sugarcane Borer Larvae2,3

In the laboratory, sugarcane borers (SCB), Diatraca saccharalis (F.), parasitized as 3rd-, 4th-, or early 5th-stage larvae by the tachinid, Lixophaga diatracae (Townsend), consumed less food and gained less weight than comparable unparasitized larvae. Parasitized larvae retained a greater percentage of ingested food than did the unparasitized larvae, but unparasitized larvae were more efficient in converting the retained food to body weight. There was no statistical difference ( P > 0.05) in efficiency of utilizing ingested food for body weight between parasitized and unparasitized larvae. There was no difference in head capsule size between larvae parasitized in the 3rd-, 4th-, or 5th-stage and comparable unparasitized larvae. Significant weight differences between unparasitized male (4.7±1.6 mg) and female (6.0±1.9 mg) SCB larvae were evident as early as 9 days after eclosion.

Ultrastructural Differences between the Propagative and Dispersal Forms in Pine Wood Nematode, Bursaphelenchus lignicolus, with Reference to the Survival

The ultrastructure of cuticle and intestine was compared between the dispersal and propagative forms of Bursaphelenchus lignicolus. With growth of the propagative form, the thickness of cuticle increased gradually, while the ratio of cuticle to body diameter decreased. The cuticle of dispersal 3rd-stage larvae (LXIIIs) was the thickest of all stages in the two forms. In the dispersal 4th-stage larvae (LXIVs), the ratio of basal layer was the largest (67% of cuticle). The external cortical layer was thicker in the dispersal form than in the propagative one. The large electron-lucent lipid droplets deposited deeply in the intestinal and hypodermal cells of LXIIIs. These lipid droplets were partly mobilized to glycogen granules with a development of LXIIIs to LXIVs.

The effect of previous desiccation on the ability of 4th-stage larvae ofDitylenchus dipsacito control rate of water loss and to survive drying

The desiccation survival of 4th-stage larvae ofDitylenchus dipsacirevived from dry worm aggregations (‘wool’ larvae) was compared with that of larvae extracted from narcissus bulbs (‘bulb’ larvae). Both sorts survived desiccation well, but ‘wool’ larvae survived desiccation at various humidities somewhat better than ‘bulb’ larvae. The rate of drying of the former was more rapid than that of the latter; the ability to control water loss, therefore, does not of itself ensure survival. The number of larvae reviving decreased with repeated cycles of desiccation and hydration, and also with the increase in the period during which the nematodes were kept dry. However, this was not associated with any loss of ability to control drying. The rate of drying of ‘wool’ larvae remained unaltered irrespective of previous desiccation treatment. In contrast, the rate of drying of ‘bulb’ larvae was more rapid after an initial desiccation with the result that ‘bulb’ larvae dried at the same rate as ‘wool’ larvae. While ‘wool’ and ‘bull’ larvae differed initially in both the rate of water loss and survival, a period of desiccation eliminated only the difference in water loss.The results suggest that the rate of drying is dependent largely on physical factors. It was shown, however, that the cuticle of dead larvae was completely permeable to water in both directions. Therefore the ability to control water loss must, in some as yet unknown way, be connected with the nematode as a living system.

Biology of Mesochorus nigripes:1 a Hyperparasite of Bathyplectes Spp.1,2

Mesochorus nigripes Ratzeburg is an indirect solitary hyperparasite of Bathyplectes stenostigma (Thomson) and B. curculionis (Thomson). Females lay single eggs in larvae of these parasites which are within larvae of the alfalfa weevil. The egg is hymenopteriform and continually enlarges from oviposition to eclosion. The 1st stage larvae eclose in 43–100 h. Once this stage reaches maximum size, the larva becomes quiescent and overwinters. The larva molts to the 2nd instar with the onset of warm spring weather. Both 2nd and 3rd stages require ca. 3 days for completion. The 4th stage larva matures in 4–5 days. Pupation requires 7–8 days for completion. Females emerge in 16–21 days at 26.7°C. Males were not found in field collections or in laboratory rearings. The initial hyperparasitism of the larval parasites ranged as high as 30% in newly-infested fields, but dropped and has remained relatively constant at 10% in older infestations. This reduction may be a natural phenomenon caused by environmental pressure or it may be due to a normal cyclical fluctuation in the population. The spread of this hyperparasite to other nearby states appears inevitable.