Egg Rafts Research Articles

The Bionomics of Culiseta melanura and Culiseta morsitans dyari in Central New York State (Diptera: Culicidae)1

Culiseta melanura (Coquillett) were found to overwinter as 4th instars and were trivoltine at this latitude. Logs were preferred resting sites of blood engorged, parous, and gravid females and males. Nullipars were more common in artificial resting boxes. Culiseta morsitans dyari (Theobald) larvae were found mainly with spring Aedes and did not occur after June. Their habitat was less specific than C. melanura and adults preferred resting logs to boxes and did not disperse as rapidly as C. melanura. C. morsitans dyari were univoltine and ♀ were long-lived with the ability to complete at least 3 gonotrophic cycles. In central New York State over-wintering was probably in the egg stage and adults preferred birds as hosts. Adults of both species laid egg rafts and were nocturnal. Parous ♀ were more attracted to light traps and nullipars were more common in resting sites.

室内条件下におけるアカイエカおよびコガタアカイエカに対する PH 60-40 の致死効果

We have evaluated lethal effects of the insect growth regulator, PH 60-40 [N-(4-chlorophenyl)-N'-(2,6-difluorobenzoyl) urea], against the larvae of Culex pipiens pallens and Culex tritaeniorhynchus. A 25% wettable powder formulation of PH 60-40 was used for the tests. All test were conducted in 300ml glass vessels each containing 200ml of distilled and deionized water. A certain amount of PH 60-40 was added into each vessel to make suspensions with desired concentration of the active ingredient. Twenty 3rd or 4th instar larvae were introduced in each vessel and about 10mg of dry beer yeast were added as food every 2 days. The temperature of water in these glass vessels remined at 23°±1℃. Since mortality occurs during larval molts, in the pupal stage, and at the unsuccessful emergence of adults, all of these forms were checked every day until all survived larvae became adults to determine total or cumulative mortality. The calculated mortality, determined from the number of adult emergence, was corrected by Abbot's formula. The LC-50 dosage were obtained from eyefitted curves of the corrected percent mortality obtained at each dose. Larval emergence was not inhibited in the egg rafts of Culex pipiens pallens laid 12-18hr prior, but development of the newly hatched young larvae was. At the rate of 0.2 and 0.1 ppb PH 60-40 inhibited adult emergence almost completely. LC-50 dosages of PH 60-40 against larvae of Culex pipiens pallens were 0.035 ppb at the 3rd instar, 0.062 ppb at the 4th instar, and those against Culex tritaeniorhyncus were 0.042 ppb at 3rd instar, 0.060 ppb at the 4th instar, respectively. At the rate of 0.5 ppb, adult emergence from the 4th instar larvae of Culex pipiens pallens was completely inhibited, even larvae tested were introduced 7 days after the treated medium prepared. However, at the rate of 0.125 ppb concentration the lethal effects were decreased after 7 days definitely. In conclusion, PH 60-40 possess a significant lethal activity against the larvae of Culex pipiens pallens and Culex tritaeniorhynchus and appears to be a promissing candidate for mosquito controlling agent.

Postemergence Effects of Two Insect Growth Regulators on the Mosquito Culex Tarsalis (Diptera: Culicidae)

After treating 4th-instar larvae of Culex tarsalis Coquillett at 0.1 and 1 ppb of Altosid™ [Isopropyl (2E,4E)-11-methoxy-3,7,11,-trimethyl-2,4-dodecadienoate] and 0.1 and 0.4 ppb of TH-6040 [1-(4-chlorophenyl)-3(2,6-difluorobenzoyl) urea], the adult mortality, fecundity, and egg viability of the resulting adults were assessed and compared with the checks. There was no significant difference in mortality of adults resulting from any of the treatments and that of checks except in the 0.4 ppb TH-6040 treatment where postemergence adult mortality was significantly greater than that in the checks and the other treatments. Adults resulting from 4th-instar larvae treated at 0.4 ppb of TH-6040 produced 43% fewer eggs/female than did the controls, but the greater adult mortality from this concentration was the main reason for this occurrence. When the number of eggs/female-day was calculated, it was found that adults resulting from the 0.4 ppb TH-6040-treated population did not produce fewer eggs/female-day than the controls. However, a 25% reduction in number of eggs/female-day was noted in the 1.0 ppb Altosid treatment relative to the untreated females. As a whole there was a 5% and 14% reduction in number of egg rafts resulting from the 0.1 and 1 ppb Altosid treatments, respectively. There was also a 12% increase and a 40% decrease in number of egg rafts in the 0.1 and 0.4 ppb TH-6040 treatments, respectively. Egg viability was affected at the higher rate (1 ppb) of Altosid, where 30% reduction was obtained. Mosquitoes treated with 0.1 ppb Altosid, 0.1 and 0.4 ppb TH-6040 showed no appreciable difference in percentage of egg hatch. The yield of progeny of adults from the higher rates of both insect growth regulators was depressed in the order of 36–38% in the treatments, as compared to the progeny in the control populations.

FIELD TEST OF AN AUTOCIDAL CONTROL METHOD WITH THE FERAL MOSQUITO CULEX RESTUANS (DIPTERA: CULICIDAE)

AbstractAn autocidal control method involving attraction of ovipositing females to artificial oviposition sites, rearing and chemical sterilization of adults reared from the collected eggs, and release of sterilized males back into the system was field tested with the mosquito Culex restuans Theobald. This species cannot be cultured continuously. The average weekly percentage of sterile egg rafts was 2.4 (range 0.3–16.0) in the test area where sterile males were released (av. 9620/wk) and 5.3 (range 1.5–30.0) in the area where both sterile males (av. 7000/wk) and untreated females (av. 4590/wk) were released. The low level of sterility achieved is attributed to infiltration of gravid females from outside the experimental areas, poor efficiency in producing sterile males from the collected egg rafts, and the small scale of the test.A hypothetical model is used to compare theoretical reduction in rates of increase of a population of mosquitoes when various proportions are induced to oviposit in ‘trap’ pools if the eggs trapped are destroyed, reared to produce sterile males for release, or reared to produce sterile males for release in conjunction with larvicidal treatment of uncontrolled breeding areas.

Comperative studies with Culex pipiens egg rafts. Immunogenetic, electrophoretic and enzymatic analysis of unfertilized, compatible and incompatible fertilized eggs

By applying immunologic, electrophoretic and enzymatic methods, extracts of different raft types of Culex pipiens were analysed. Rafts of the crosses Pa x Pa and Ha x Ha contained four common antigens, while unfertilized rafts of Pa and Ha (no antisera were prepared against them) and rafts of the crosses Og x Og, Og x Pa, and Pa x Og shared three common antigens with the remaining raft extracts. Disk-electrophoresis of raft extracts in acrylamide gel resulted in different electropherograms. Ten protein bands were common to all these raft types. The unfertilized rafts of Pa and Ha yielded three more protein bands, the crosses Pa x Ha and Ha x Pa one more, the crosses Og x Og and Pa x Og three more, and Og x Pa two more. Many enzymes were demonstrated in the raft extracts after they were separated in acrylamide gel and incubated with the corresponding substrate solutions. All the raft types possessed one enzyme type for glutaminate-, lactate-, glucose-6-phosphate-dehydrogenase and catalase. Malate-dehydrogenase and leucine aminopeptidase occurred in each raft type as two isoenzymes. Alkaline phosphatase was observed as a single enzyme, but was lacking in rafts of the crosses Pa X Pa and Ha X Ha. While rafts of the crosses Og x Og and Og x Pa possessed two acid phosphatases, three could be demonstrated for the remaining raft types. Up to eight esterases appeared; rafts of the crosses Og x Og and Og x Pa possessed seven such activities. The results obtained by the Ouchterlony test, disk-electrophoresis and the histochemical enzyme tests are discussed in context and checked according to the phenomenon of incompatibility.

アカイエカ発生源対策におけるグッピー Poecilia reticulata 利用の基礎的研究 : 第 2 報発生源での捕食の効率

Experiments were carried out with two guppies in each of 200 liter tanks placed outdoors under natural summer condition of Tokyo; water temperature was around 25-27℃. There was a control tank for each of the above experimental tanks. Five egg rafts of Culex pipiens pallens were given each morning for seven days. Each egg raft contained an average of 249 eggs. It was observed that guppies pecked at and ate the rafts; the number eaten was estimated at three rafts per day. Some of the larvae had hatched from the eggs, but it was difficult to estimate the number which did because of their small size. In any case, no larvae were found on the eighth morning. In order to determine the number of larvae of different developmental stages which was eaten per day, various stage of larvae were introduced in each tank. When 2,000 larvae, which had recently hatched from egg were supplied, it was noted that 369 of them had pupated after six to ten days. In the control tank wherein there were no guppies 1,614 larvae survived and pupated. It was estimated that 386 of the original 2,000 larvae in the control tank died naturally. If one assumes that an approximately equal number of larvae will die naturally in the experimental tank, then the actual number of larvae consumed was estimated at 1,245,or (2,000-369)-(2,000-1,614), during the larval period. When 500 larvae of age three days after hatching were supplied in the same way as mentioned above, the number of larvae eaten was estimated at 249 larvae by the end of the pupation period; under similar conditions, 142 four-day larvae were consumed; 50 five-day larvae; and 35 six-day were eaten. From the above the number of larvae eaten per day was calculated in the case of 0 to two days old larvae as : (1245-249)/3=332 larvae. In the same way, 107 three-day old larvae, 92 four-day old and 15 five-day old larvae were eaten per day. When a mixed-age population of larvae were supplied, the number eaten was greater in younger-aged larvae than older ones. However, some older ones were always eaten in spite of the presence of young larvae still remaining in the tank, although the number of older larvae consumed was less in comparison when a homogeneous age-group population was available.

アカイエカ発生源対策におけるグッピー Poecilia reticulata 利用の基礎的研究 : 第 3 報野外実験特に殺虫剤との共用

Four tanks, labeled A, B, C, and D, containing 750 liters of water, were placed outdoors near the laboratory. Breeding of Culex pipiens pallens was found in each tank in early June, 1972. Twenty guppies, or 10 mature pairs, were introduced in two of the tanks, B and C, on 9 June 1972. Tank B was then treated with fenitrothion 1ppm, tank C remained untreated. Tank D was treated with fenitrothion 1ppm on the same day, and tank A, the control tank, received neither guppies nor fenitrothion. The observation for each tank was conducted using a ladle to count the larvae and pupae densities every two or three days. Also counts of total number of egg rafts on the water surface were made on the same day. These observations were made until the end of September. According to the results, the larvae and pupae dramatically disappeared on the fourth day after fenitrothion treatment in both tanks B and D. In the case of tank D, the chemical treatment had to be repeated five times during a two-month period due to the outbreak of larvae every 10 or 20 days. Tank B, however, received no additional chemical treatment after the initial treatment because of the presences of the guppies. A number of pupae was observed for three weeks after introduction of guppies to tank C, but all pupae had disappeared by the end of this period. More than 100 rafts a day of oviposition were observed in tanks A and D. However, no rafts were recognized from tanks B and C, except for very few days during the peak time of oviposition activity of mid-summer. As Part II of the present report series showed, these egg rafts were eaten by guppies in each tank. Thus, in tanks B and C no adult mosquitoes emerged throughout the summer season.

名古屋地方における蚊族個体群の発生動態 : III. アカイエカ幼虫個体群と成虫個体群とにおける発生動態の関連性

An ecological study was made on the larval and imaginal populations of the house mosquito, Culex pipiens pallens Coquillett, in Nagoya City during a period April to November, 1969. The purpose of this report is to elucidate relationship between larval and imaginal population dynamics in natural habitat from the view points of seasonal change of larval population size, larval age structure, imaginal population size and parous rate of adult females. 1) The number of larvae and pupae in a fertilizer pit was estimated by the removal method (Fig. 2), and totalled 11,962 during the study period. Most of them (ca. 98%) were Culex pipiens pallens and the rest were C. tritaeniorhynchus, C. vorax, Anopheles sinensis and Aedes togoi (Table 1). In the vicinity of the fertilizer pit, a total of 123 adult mosquitoes were captured by a light trap during the same period. They consisted of 61% C. tritaeniorhynchus, 38% C. pipiens pallens and about 1% An. sinensis (Table 2). 2) The larval population of C. pipiens pallens occurred from late April to early November, and the population size reached its peaks during late May to early June and in early October (Table 1). Larval age structure was analyzed consecutively and, on the basis of the precursory abundance of the older larvae and pupae, adult emergence at population level was considered to occur about six times. Of these, number of newly emerged adults was estimated to be the largest at the second emergence period (late May-early June) and the next largest at the fifth emergence (late September-early October)(Fig. 3). 3) On the other hand, imaginal population of the species observed by a light trap occurred from early April to early November, and the population size reached its peak in July, after the first peak of productivity of adults observed in the larval population. The second peak of productivity in autumn, however, was not followed by the prominent peak in adult population size (Fig. 3). Parous rate of adult females rose remarkably in early May and during late September to early October, and number of egg rafts in the fertilizer pit increased in parallel with the rises of the parous rate (Fig. 3). 4) Life cycle of the house mosquito in spring in this district was summarized as follows : (a) Completion of overwintering of the adults around March to mid April, (b) appearance of the first larval population in late April, (c) appearance of imaginal population in early May.

A high incidence of green coloration in newly-emerged adult populations of Culex pipiens fatigans in Rangoon, Burma.

Wild adult females of C. pipiens fatigatis in Rangoon exhibit a distinctive green coloration on emergence. The color can be seen through non-dorsal areas of the integument. It persists for about 2 and 3 days respectively, in the thorax and abdomen. Excretion, or egestion, or both, of green material partly accounts for the loss of color in unfed nullipars. Green unfed females are nulliparous, permitting simple age grading without dissection. Green color also occurs in freshly-laid egg rafts, fourth-instar larvae, and the ovaries of gravid females. Some wild engorged females have green-colored thoraxes, indieating feeding can begin within 48 hr after emergence.

An oviposition pheromone associated with the egg rafts of Culex tarsalis.

The response of gravid mosquitoes, Culex tarsalis Coquillett, at 3 densities to egg rafts of their own species demonstrated an egg-associated pheromone which attracts females to oviposit. Olfactometer tests with this material showed significantly greater mosquito attraction to the oviposition pheromone than to distilled water. Gravid Culex pipiens pipiens L., and Aedes aegypti (L.), did not respond to the C. tarsalis pheromone, which fact indicates that it may be species specific. Preliminary analysis of this chemical indicates other solubility, a lipid nature, and low vapor pressure.

Overcrowding factors of mosquito larvae. 2. Growth-retarding and bacteriostatic effects of the overcrowding factors of mosquito larvae.

LT50, values of the overcrowding factors based on continuous exposure of 1st-stage larvae of Culex pipiens quinquefasciatus Say were 1.4, 5.6, and 6.4 days for 1, ½, and ¼ unit of the factors, respectively, while LD50 was 0.31 unit. The overcrowding factors also retarded larval growth; 1 unit of these factors facilitated only 0.6% of the 1st instars to pupate on the 16th day from the start of the exposure, whereas 68.2% of the untreated larvae pupated, and the median pupation time was reached on the 10th day. First and 2nd instars were more vulnerable in terms of growth delay as well as mortality. Reduction in sizes of the egg rafts laid by females resulting from treated larvae also was noticed. Bacteriostatic or bactericidal activity of the overcrowding factors was shown by determining the number of bacteria in the treated waters and by testing the factors against Bacillus thuringiensis Berliner on nutrient agar. The rate of heartbeat was depressed markedly in larvae treated with these factors as compared with untreated larvae. Reduction in bacterial numbers in the treated water and reduced rates of heartbeat of mosquito larvae are partly responsible for high mortality and growth retardation.

Studies on the life cycle of Culex pipiens pallens in Korea

The present studies were carried out, under natural room condition from June to July in 1969. 1. The period required for growth of eggs and larva varied according to various temperatures and methods of rearing. 2. The average number of eggs laid by the Culex pipiens pallens was 137 per egg raft. 3. The period of gonotrophic cycle was from 3 to 6 days: incubation period of eggs was from 1.5 to 2 days; larva period was from 10 to 14 days: pupa period was from 2 to 3 days. Accordingly, the period from the beginning of gonotrophic cycle to the adult mosquitos in next generation required 25 days at the longest and 16.5 days at the shortest.

Taxonomic and ecological notes on Culex (Melanoconion) Spissipes (Theobald).

Eggs, larvae and pupae of C1lle.u (Melanoconion) spissipes (Theobaldj wrere collected from the margins of Nariva Swamp '(Bush Bush Forest), Trinidad, W. I. The reared adults were studied for variation in mesonotal scale pattern. Culex (M.) merytes Dyar is newly synonymized with Culex @is- sijws in this paper as a result of the variation observed, and the synonymy of C. (iv.) fur Dyar & Knab was also confirmed, Natural larval habitats and oviposition sites of this species are discussed. distributed in Trinidad. It is a common inhabitant of the shaded swamp forest surrounding Bush Bush Island in the Nariva Swamp. Typical females display the anterior l/2 to 2/3 of the mesonotum completely adorned with straw- colored scales and with the posterior portion largely dark brown-scaled. This mesonotal pattern has been 1 of the most important characters for identify- ing the species. Examination of many adults col- lected from mouse-baited mosquito traps (Worth & Jonkers 1962) operated in Bush Bush Forest as well as adults reared from individual egg rafts or from immature stages collected at the swamp margin demonstrated the mesonotal pattern to be highly variable. This variation has created taxonomic confusion and at least 3 Latin names have been used for the species. This report attempts to clarify the synonymy and contributes a few ecological notes on the larvae as they occur in nature. The char- acter of the immature stages of this species will not be discussed in this paper, but it will be given later by another author. VARIATION IN ADULTS

Ovicidal activity of aliphatic amines and petroleum oil against two species of mosquitoes.

Most of the homologous series of primary lymphatic amines (long alkyl chains) proved highly effective against eggs of Anopheles albimanus Wireman, but only one of these (solely Maine) proved effective against eggs of the southern house mosquito, Culex pippins quinquefasciatus Say. A beta Maine (beta penta decane amine) also proved effective at 10 ppm concentration against the former species but not against the latter. Species specificity may be attributed to the variations in chorion and micropylar structures and their functioning in the 2 species. Age of eggs as well as duration of treatment period influenced level of susceptibility of eggs to oleyl amine and Neopynamin® (2,2-dimethyl-3-(2-methylpropenyl)cyclopro-panecarboxylic acid ester with N -(hydroxymethyl)-1-cyclo-hexene-1,2-dicarboximide). The younger eggs (1-8 hours old) were more susceptible than older eggs. Longer treatment period (48 hours) produced higher kill of the eggs than a shorter treatment period (24 hours). Exposure periods of shorter than 24 hours produced no marked effects. A kerosene-type petroleum oil (Toxisol J. A. (Jet Aviation grade)) killed eggs of C. p. quinquefasciatus at concentrations of 25 ppm or higher. At these higher concentrations the surface tension of water and/or eggs was lowered to such an extent that the egg rafts sank and mortality in these eggs was high. Mechanical sinking of egg rafts caused similar high mortality of eggs. Embryonic development in eggs treated with effective concentrations was generally retarded. Most of the embryos treated showed no differentiation or were found at the earlier stages of differentiation. However, some embryos in the treated eggs reached full maturity but were not able to emerge.

Effect of Gamma Irradiation on Female Culex pipiens quinquefasciatus

Female Culex pipiens quinquefasciatus Say were exposed to 2000 to 9000 R of gamma irradiation as 1-day-old pupae. The average number of eggs per egg raft decreased with an increase in dose, and at 7000 R and above no eggs were deposited. The sterility produced by the different exposures ranged from 12% at 2000 R to 60% at 6000 R. It appears that complete female sterility due to gamma irradiation is accomplished by inhibiting egg production rather than by inducing the production of all sterile eggs.

Mist Application of Chemosterilants to Adult Male Culex pipiens quinquefasciatus1

To determine the comparative effectiveness of 3 chemosterilants on male southern house mosquitoes, Culex pipiens quinquefasciatus Say, virgin males 4-days old were exposed to mists of apholate, tepa, and metepa in an 85:15 mixture of ethanol:glycerol with a modified Hoskins-Caldwell spray chamber. Twenty-four hours later these were combined with virgin females and maintained as small colonies. Life span was not altered, normal mating and oviposition occurred, and normal numbers of eggs were produced. The egg rafts were collected daily, isolated and identified, and subsequent hatch was determined. Apholate proved to be the most active chemosterilant, followed by tepa and metepa in that order. A 2% concentration of apholate produced sterility of 95% or better. A 4% concentration of tepa and an 8% concentration of metepa were required to produce similar malesterility. The use of such a rapid, simple, and consistent technique for applying chemosterilants directly to the test specimens permits valid comparisons of biological activity by negating such varied problems as unequal evaporation, polymerization of compounds, and tarsal uptake from residues.

Microsporidia in Pennsylvania mosquitoes

Aedes canadensis (Theobald) larvae infected with a Thelohania were taken from two different localities in Pennsylvania. The pathogens were determined to be Thelohania inimica Kellen and Wills, and assigned to a new subspecies, Thelohania inimica canadensis. This constitutes the first microsporidian infection reported from Aedes canadensis (Theobald). Thelohania obesa Kudo was found in a single larva of Anopheles quadrimaculatus Say, confirming this mosquito as its host. Stempellia magna Kudo was recovered from larvae of Culex restuans Theobald that were reared from egg rafts collected in the wild, suggesting that transovarian transmission of this parasite occurs in nature.

Surfactant in Apical Drop of Eggs of Some Culicine Mosquitoes1

The apical drop found on the posterior end of eggs of species of Culex and Culiseta , described in the recent literature as being water, exhibits high surface activity and chemically seems to be an ester of several fatty acids. The apical drop appears to play a role in returning upset egg rafts to their normal position on the water surface.

Spawning Behavior and Egg Raft Morphology of the Ocellated Fringed Frogfish, Antennarius nummifer (Cuvier)

Spawning Behavior and Egg Raft Morphology of the Ocellated Fringed Frogfish, Antennarius nummifer (Cuvier)

Parthenogenesis in Culex fatigans

Parthenogenesis occurs in the mosquito Culex fatigans. Three larvae were hatched from 85,851 eggs in tests of eggs from 1001 females. There were 618 egg rafts; the three larvae were from different rafts.