Über die Entwicklung der Eikapselvolumina bei verschiedenen Opisthobranchier-Arten (Mollusca,Gastropoda)

An attempt has been made to estimate the volumes of eggs and egg-capsules employing the formula for the rotation-ellipsoid, first after oviposition, second for the capsules during different stages of embryonic development until hatching. The results of the calculations permitted analysis of: (a) the relationship between egg-case volume and egg volume immediately after oviposition; (b) the size of capsules during development until hatching; (c) the relationship of the capsule volume at hatching in comparison to that after oviposition (enlargement-factor).Placida dendritica shows no increase in capsule volume during development.Gonidoris nodosa, Rostanga rufescens, Trinchesia viridis, Acanthadoris pilosa, Archidoris pseudoargus, Tritonia hombergi andAeolidia papillosa show a distinct increase in capsule volume at the time of velarcilia appearance. The degree of egg-case enlargement and the time of its beginning reveal interspecific differences; within some of the species, both also depend on the number of larvae present in the egg-case. The reasons for such behaviour are not yet known; some possible explanations are discussed.     

Biochemical and physiological studies of certain ticks (Ixodoidea): specific gravity of hemolymph and coxal and gut fluids of Argas (Persicargas) persicus and Argas (Persicargas) arboreus (Argasidae)

Specific gravity (sp. gr.) of cell-free hemolymph and gut and coxal fluids was determined at different states of the gonotrophic cycle (unfed + 15 days, engorgement day before and after coxal fluid emission, engorgement + 1 day, oviposition day, and oviposition completion + 1 day) of female Argas (Persicargas) persicus and A. (P.) aboreus (Argasidae). The patterns of hemolymph and gut fluid sp. gr. change differed from each other during the gonotrophic cycle, but both patterns were similar in the 2 Argas species. Hemolymph sp. gr. decreased to a minimum one day after feeding (1.0085 and 1.0081 for persicus and arboreus, respectively), and increased through oviposition to a maximum on oviposition + 1 day (1.0187 and 1.0221). Minimum gut fluid sp. gr. occurred on engorgement day before coxal fluid emission (1.0565 and 1.0697). Afterward, gut fluid sp. gr. increased to a maximum on engorgement day + 1 for persicus (1.1089) and on oviposition day for arboreus (1.0973), and then decreased during oviposition in both species. In each tested state of each species, the sp. gr. was consistently higher in gut fluid than in hemolymph. In each species, coxal fluid and hemolymph sp. gr. were the same on engorgement day.     

Better Hosts Dive: Detachment of Ectoparasitic Water Mites (Hydrachnellae: Arrenuridae) from Damselflies (Odonata: Coenagrionidae)

Water mite larvae parasitizing damselflies must detach while the host is in a suitable reproduction habitat for both parasites and itself. They should do so during the host's oviposition. In this paper I present experimental data for the detachment rate of water mite larvae (Arrenurus cuspidator) from different host species, Coenagrion hastulatum and C. puella, in relation to the host's oviposition behavior. C. hastulatum oviposits submerged, whereas C. puella oviposits at the water surface and aggregates with conspecifics. It was found that mite larvae detach at a significantly higher ratio from hosts with submerged oviposition. Experimental tests showed that this is not a species-specific effect. It is caused mainly by the oviposition behavior. The results are discussed in the light of different oviposition systems in damselflies.     

Effects of male-female rations on mating and egg production in Octomyomermis muspratti (Mermithidae: Nematoda)

Octomyomermis muspratti, a mermithid parasite of mosquito larvae, molted to the adult stage in 4–16 days. When male-female ratios were relatively high (1:2), mating and oviposition began soon after maturation, and oviposition was completed in 21–40 days. The number of females developing eggs increased with a corresponding increase in the male-female ratio. About 60% of the females completed oviposition at male-female ratios of 1:20, and about 100% completed oviposition as the male-female ratios were increased to 1:2. No egg development was observed in the absence of males. Male O. muspratti were capable of mating with a number of females and remained reproductively active for at least 50 days after a maturation at 26–28°C.     

Ovarian cycle in immature and adult stages ofTrichogramma cacoeciae andT. Brassicae (Hym.: Trichogrammatidae)

The ovarian cycle was studied in two species ofTrichogramma, the thelytokousT. cacoeciae and the arrhenotokousT. brassicae. For both species, egg development was recorded (1) in the immature stages (2) in adult females before and after one bout of oviposition. The two species differed in the numbers of immature eggs formed and stored in the ovaries, and in the pattern of egg replenishment after oviposition.     

Phycomycetes parasitizing the ovaries of blackflies (simuliidae)

The developmental stages of the fungus in the ovary and freshwater are discussed. Based on the evidence to date the simuliid host is infected in the early larval instars. Parasitism results in a destruction of the ovarian tissues with no or few eggs produced. The fungus replaces the ovarian tissue and produces massive numbers of spores which are released by the female fly at the time of oviposition. After oviposition, infected flies do not seek a blood meal. Longevity of the host does not appear to be affected by the presence of the fungus. The spores released by the fly during oviposition did not withstand desiccation and did not develop on the artificial media tested; development occurs only in water. Development of sporangia takes 5 to 7 days at 4°C, and 2 to 3 days at temperatures above 10°C. The developmental process in spores from S. verecundum was followed from the formation of sporangia to the opening of discharge tubes which zoospores were presumed to be released but not observed.     

Weather Variability Associated with Aedes (Stegomyia) aegypti (Dengue Vector) Oviposition Dynamics in Northwestern Argentina

This study aims to develop a forecasting model by assessing the weather variability associated with seasonal fluctuation of Aedes aegypti oviposition dynamic at a city level in Orán, in northwestern Argentina. Oviposition dynamics were assessed by weekly monitoring of 90 ovitraps in the urban area during 2005-2007. Correlations were performed between the number of eggs collected weekly and weather variables (rainfall, photoperiod, vapor pressure of water, temperature, and relative humidity) with and without time lags (1 to 6 weeks). A stepwise multiple linear regression analysis was performed with the set of meteorological variables from the first year of study with the variables in the time lags that best correlated with the oviposition. Model validation was conducted using the data from the second year of study (October 2006- 2007). Minimum temperature and rainfall were the most important variables. No eggs were found at temperatures below 10°C. The most significant time lags were 3 weeks for minimum temperature and rains, 3 weeks for water vapor pressure, and 6 weeks for maximum temperature. Aedes aegypti could be expected in Orán three weeks after rains with adequate min temperatures. The best-fit forecasting model for the combined meteorological variables explained 70 % of the variance (adj. R²). The correlation between Ae. aegypti oviposition observed and estimated by the forecasting model resulted in r_s = 0.80 (P < 0.05). The forecasting model developed would allow prediction of increases and decreases in the Ae. aegypti oviposition activity based on meteorological data for Orán city and, according to the meteorological variables, vector activity can be predicted three or four weeks in advance.     

Effects of some insect growth regulators on natural enemies of scale insects (Hom.: Coccoidea)

We report and discuss effects of four insect growth regulators: buprofezin, fenoxycarb pyriproxyfen and chlorfluazuron, at concentrations recommended for agricultural use on six species of natural enemies of homopteran pests. Dipping in buprofezin had no appreciable effect on adult mortality, oviposition and development ofComperiella bifasciata (Howard), (Hymenoptera: Encyrtidae). When exposed to hosts treated with buprofezin, percentage mortality of adultEncyrtus infelix Embleton (Encyrtidae) was low; buprofezin had some detrimental effect on immature stages ofE. infelix when applied prior to parasitization, but not when introduced after parasitization. Buprofezin had a slight effect on the immature stages ofCryptochaetum iceryae Williston (Diptera: Cryptochaetidae), while fenoxycarb and pyriproxyfen had marked detrimental effects on parasitization and/or development of the parasitoid fly. None of the larvae ofRodolia cardinalis Mulsant (Coleoptera: Coccinellidae) developed into adults after application of buprofezin, fenoxycarb or pyriproxyfen. Buprofezin and chlorfluazuron completely prevented egg hatch ofChilocorus bipustulatus L. (Coleoptera: Coccinellidae). Buprofezin did not adversely affect egg hatch and larval development ofElatophilus hebraicus Pericart (Hemiptera: Anthocoridae); fenoxycarb or pyriproxyfen applied either before or after oviposition on pine needles caused total suppression of egg hatch.     

Temperature-dependent development and oviposition models of Ramulus irregulariterdentatus (Phasmida: Phasmatidae)

Public interest in Ramulus irregulariterdentatus as a pet insect in Korea is increasing, although it is also considered as a potential forest insect pest. The objective of this study was to construct development and oviposition models of R. irregulariterdentatus. Development rates were fitted with a nonlinear Briére model which estimated optimal temperatures to be 24.5 and 26.2?°C with upper development thresholds of 29.3 and 31.4?°C for egg and nymph, respectively. In a linear model, lower development thresholds were 7.6 and 5.2?°C for egg and nymph, respectively. Survivorship was the highest at 21.0 and 22.2?°C for egg and nymph, respectively. Mean fecundity ranged from 14.4 eggs at 17.5?°C to 32.0 eggs at 23.5?°C. It was fitted to an extreme value function. Adult survival and cumulative oviposition rate of R. irregulariterdentatus were fitted to a sigmoid function and a two-parameter Weibull function, respectively. These models can be used to forecast phenology and population dynamics of R. irregulariterdentatus in the fields and optimize environmental conditions for rearing R. irregulariterdentatus.     

Bionomics of Orasema simplex (Hymenoptera: Eucharitidae), a parasitoid of Solenopsis fire ants (Hymenoptera: Formicidae) in Argentina

Biological characteristics of the parasitoid Orasema simplex Heraty (Hymenoptera: Eucharitidae), a potential candidate for the biological control of fire ants in the United States were investigated. Female survivorship, fertility and oviposition preferences were studied in the laboratory. Naturally parasitized colonies were examined to determine offspring sex ratio, development success and time, and to artificially parasitize healthy ant colonies. In addition, field studies were carried out to establish natural oviposition substrates and adult activity patterns. Orasema simplex female survivorship was 3.6 ± 1.5 days. Newly emerged females contained 613.5 ± 114.0 mature eggs. The adult development success in natural parasitized colonies was 22.2% with a female-biased sex ratio (4:1). The time required from planidia to adult was 29.5 ± 5.4 days. In the field, adults were mostly found around the ant nests at midday. A broad range of plant species was observed as oviposition substrates. The transfer of planidia to healthy ant colonies was achieved but the development success was very low. Orasema simplex appears to have a limited potential as a fire ant biocontrol agent because of cosmetic damage to a wide variety of plants used for oviposition. However, further studies are necessary to evaluate the real damage exerted by oviposition punctures.     

An observation on the embryonic development in Thrips palmi (Thysanoptera: Thripidae) eggs obtained by an artificial oviposition setup

Thrips palmi is an important insect pest of vegetables and ornamental crops worldwide. Besides direct damage caused by feeding, it transmits several tospoviruses in a persistent-propagative manner. Eggs of T. palmi are microscopic and embedded within plant tissue by the sharp ovipositor of adult female. In the present study, an artificial oviposition setup has been standardized for T. palmi. Eggs of T. palmi were harvested in sterile water between two thin membranes. The developmental stages of T. palmi embryo were studied starting from oviposition up to hatching by inverted and confocal reflection microscopy. Energids were homogeneously distributed at an early stage of development. The anterior end of the egg curved with a constriction post 38 h. Initiation of tissue organization, mouthparts, appendages, compound eyes were observed at different time points. Appendages were well developed and segmentation was prominent post 70 h. The embryo was completely developed at around 80 h and hatched by 86 h post oviposition at 28 °C temperature. The study first time reports the embryonic development of T. palmi that would be helpful in detailed investigations of thrips developmental biology and evolution.     

Morphology and ultrastructure of the serosal cells (teratocytes) in Cardiochiles nigriceps Viereck (Hymenoptera : Braconidae) embryos

The morphogenetic changes of the serosal membrane during embryonic development of Cardiochiles nigriceps Viereck (Hymenoptera : Braconidae) were investigated. Eggs observed soon after oviposition into the natural host Heliothis virescens (F.) (Lepidoptera, Noctuidae) showed a transparent chorion and a uniform texture. After 5 hr, the embryo exhibited a distinct granular appearance and by 12 hr attained the germ band stage. A serosal membrane originated from the anterior pole of the embryo between 14 and 15 hr after the egg was laid, eventually forming with the cells both in the anterior and posterior pole a continuous envelope around the developing embryo.Ultrastructural observations revealed that the serosal cells in contact with the abdominal region of the embryo, beginning 24–25 hr after oviposition, formed a syncytium. However, the syncytial tissue did not extend to the cells around the head and thorax. The serosal cells at both embryo poles increased in size without losing their structural organization, and developed into teratocytes when the larva hatched. In contrast, the serosal cells surrounding the body of the embryo persisted longer on the head and thorax region of the newly hatched larva, while the syncytial tissue degraded more rapidly after hatching.In vitro rearing experiments showed that C. nigriceps embryos removed from parasitized host larvae just before and just after serosa formation, hatched only when the medium used was formulated with the addition of fetal bovine serum. Embryos did not develop or hatch when placed in a serum-free medium. Once the syncytium deriving from the serosal membrane became evident, embryos readily developed and hatched in serumfree media. The results of this study seem to suggest that the serosal embryonic membrane could have a nutritional role for the developing parasitoid embryo.     

Effect of temperature on queen oviposition and seasonal colony development in <Emphasis Type="Italic">Lasius japonicus</Emphasis> (Hymenoptera: Formicidae)

Although day length plays a critical role in the seasonal development of many temperate insects, this study showed that this variable is less important than temperature for seasonal regulation of an ant’s life cycle. Here, we examined the effects of temperature on queen oviposition and seasonal colony development of Lasius japonicus Santschi. Queens were collected soon after their nuptial flight and were reared under constant laboratory conditions; colony development was analyzed. The percentage of larvae- and pupae-emerged colonies was reduced in low rearing temperatures, indicating that temperature is the primary environmental factor for the regulation of seasonal development. Larval diapause was induced at higher temperatures than the reproductive diapause of queens. Larvae need to enter diapause before winter; nevertheless, eggs that were still unhatched in late autumn would not necessarily be wasted because they could be eaten by queens. Cyclic fluctuation in the egg number was observed. At 25 °C, the second increase in egg number was synchronized with pupation, suggesting a social effect on queen oviposition. In contrast, at 20 and 17.5 °C, the clear second peak of oviposition was found in colonies wherein larvae did not emerge, suggesting that endogenous rhythmicity is involved in the regulation of queen oviposition.     

Temperature-dependent oviposition model of Scopula subpunctaria (Lepidoptera: Geometridae)

Scopula subpunctaria, is one of important defoliating insect pests of tea plants in China. However, the effect of temperature on its longevity and fecundity had not been reported, and the temperature-dependent oviposition model is lacking. The reproductive characteristics of S. subpunctaria were investigated under eight constant temperatures (13, 16, 19, 22, 25, 28, 31, and 33℃), with a 14L: 10D photoperid and 65–85% RH. The results showed that temperature significantly influence oviposition period, longevity, and fecundity of S. subpunctaria. The mean longevity of female adults increased from 10.8 days (33℃) to 33.9 days (13℃). Male lived shorter than female did. The mean longevity of males was shortest at 33℃ (8.1 days) and longest at 23.8℃ (17.6 days). Total fecundity of S. subpunctaria females ranged from 15.4 eggs at 33℃ to 279.9 eggs at 22℃. The temperature-dependent oviposition model of S. subpunctaria was constructed based on four sub-models (developmental rate model, total fecundity model, oviposition rate model, and survival rate model). The results of this study would be helpful in forecasting and predicting population occurrence of S. subpunctaria in tea plantations.     

Intermittent character of adult diapause in Aelia acuminata (Heteroptera)

The response to photoperiod of field-collected Aelia acuminata was studied by exposing insects to three photoperiodic regimes. After the completion of diapause the insects do not respond to photoperiod: in mid-February the length of the pre-oviposition period is the same under both long and short photoperiods. After the onset of oviposition, insects again become responsive to photoperiod regardless of the time of year: under long day, oviposition lasts until death, whereas under short day the females cease oviposition after about 3 weeks. After a further 2 or 3 months without ovipositing, these females which are still experiencing short-day conditions resume reproduction for a further 4–7 weeks and long-lived individuals have three oviposition periods. A regulatory mechanism is suggested for the alternation between oviposition and diapause.     

Influence of Substrate Color on Oviposition Behavior,Egg Hatchability,and Substance of Egg Origin in the Mosquito Anopheles sinensis (Wiedemann) (Diptera: Culicidae)

Understanding the factors that influence the choice of substrate for oviposition by the malaria mosquito is critical to efforts directed to the management of the disease and vector control measures aimed at modifications of larval habitat. The influence of black and white substrates on Anopheles sinensis (Wiedemann) (Culicidae: Anophelinae) female oviposition behavior and egg-hatching rate and the presence of substances associated with egg laying were studied. Results from the no-choice tests showed that the number of eggs laid on black substrate was significantly greater than that laid on white substrate. Results from the dual-choice tests revealed that gravid females showed stronger preference for the black substrate than that for the white substrate. Furthermore, the egg-hatching rate on white substrate was significantly lower than that observed on black substrate. Results from the three-choice tests showed that substance of egg origin was associated with the black substrates (UBS) that were attractive for and stimulated oviposition. The results of this study suggest that there might be some compounds in the black substrates which play a positive role in the oviposition behavior of female mosquitoes and in the development of eggs and that eggs might produce and release active substances that attract females and stimulate oviposition. These results could be important as regards to the optimization of mosquitoes raised for experimental purposes and the control of malaria mosquitoes by altering the oviposition behavior of gravid females.     

A preliminary histological investigation of gall induction in an unconventional galling system

In an unusual case involving a candidate biological control agent, the histologically complex stem galls of the weevil, Rhinusa pilosa (Coleoptera: Curculionidae) on yellow toadflax (Linaria vulgaris), are rapidly induced during oviposition and reach full size by larval hatch. To investigate gall induction, the oviposition behavior of R. pilosa was described. We experimentally disrupted ovipositing weevils at three key points in the oviposition sequence and compared host-plant tissue responses post disruption, to what occurs during normal gall induction using histological methods. De novo xylem production, intercellular spaces in the cortex, and hyperplasia and hypertrophy of the procambium and pith parenchyma surrounding the egg were some of the tissue- and cellular-level modifications observed only 3?C5?days after normal oviposition. Normal gall development was not observed after any of the oviposition disruption treatments, although some of the cellular and tissue responses resembled those found after undisrupted oviposition. Feeding by the female during oviposition canal formation induced wound meristem and callus tissue formation, but no other modifications consistent with gall formation. When females were disrupted about 20?s into oviposition, a homogenously dense substance was observed, which was suspected to be ovipositional fluid. There was minor stem swelling 10?days later and histologically, periclinal cell divisions, de novo xylem, and pith cells with numerous stained plastids were observed as in normal gall development, thus suggesting that ovipositional fluid plays a role in gall induction.     

Biological control of giant salvinia (Salvinia molesta) in a temperate region: cold tolerance and low temperature oviposition of Cyrtobagous salviniae

Success of Cyrtobagous salviniae Calder & Sands (Coleoptera: Curculionidae) for biological control of Salvinia molesta D. S. Mitchell in temperate regions has been less reliable than in tropical and subtropical regions and this difference is presumed to be due to greater winter mortality. We measured the cold tolerance of C. salviniae by comparing chill coma recovery time and survival of adults after exposure to freezing conditions among four geographic populations collected from Florida, Louisiana, Texas and Australia. Effects of winter temperature acclimation on low temperature oviposition also were determined. The Australian population was more cold tolerant than the three US populations. No oviposition by C. salviniae was observed at a water temperature of 17 °C and the oviposition rate at 19 °C was less than at 21, 23 and 25 °C. We suggest that introduction of cold tolerant strains of C. salviniae could increase its effectiveness in temperate regions of the US.     

Effect of malathion and acetylcholine on the developing larvae ofPhilosamia ricini (Lepidoptera: Saturniidae)

Feeding of malathion induces accumulation of acetylcholine inPhilosamia ricini developing larvaevia inhibition of acetyl cholinesterase activity. The insecticide also causes depletion of all nutrients, loss in weight, under-development of silk glands resulting in reduced silk production, lack of oviposition and high mortality among the insects. Acetylcholine however, while fed during the same period of development, tones up their nutritional status, induces better growth, weight gain, improved silk production and oviposition and significantly lower mortality than in the control group of insects maintained on castor leaves. This improved status of insects has been attributed to choline, the insect vitamin released from acetylcholine. Acetylcholine has also been noted to protect the insects to some extent from the poisonous effect of malathion on exposure to it after a dose of acetylcholine during the preceding instar stadium