Production Of Viable Eggs Research Articles

Effects of temperature on the reproductive life history of the black vine weevil,Otiorhynchus sulcatus

AbstractOtiorhynchus sulcatus(F.) (Coleoptera: Curculionidae) is one of the most serious pests of horticultural crops but despite this, the effects of temperature on its reproduction are not fully understood. This study investigates the effects of temperature on the full set of reproductive traits ofO. sulcatusat nine temperatures between 11 and 36 °C and develops descriptive models for each trait. Cohorts of newly eclosed adults were subjected to these temperatures and fed onRhododendronspec. leaves. Adults oviposited at temperatures from 11 to 27 °C. Significant differences among treatments were found in the preoviposition period, oviposition period, longevity, per capita egg production, and egg viability. The preoviposition period was the shortest at 24 °C and the longest at 11 °C. With a non‐linear model fitted to the data across the full range of experimental temperatures, the lower and upper threshold temperatures and optimum temperature for reproductive maturation were estimated to be 6.8, 30.0, and 22.7 °C, respectively. The developmental threshold and calculated thermal constant were estimated to be 6.7 °C and 505.0 degree‐days, respectively, using a linear model at temperatures between 11 and 21 °C. Maximum per capita egg production (1094.1 eggs) and highest egg viability (90.1%) were both observed at 21 °C. The median longevity ofO. sulcatusadults in the 18–36 °C range decreased linearly as temperatures increased. At 27 °C or above, the reproductive success ofO. sulcatuswas substantially impaired, and the optimum temperature range was 21–22 °C. Production of viable eggs in relation to temperature and weevil age was simulated by incorporating four models of life history traits, including egg production, egg viability, cumulative pattern of egg production, and adult survival. Overall, the present study demonstrates that temperature is a key factor in determining the reproductive success ofO. sulcatusadults. We hypothesize that temperature may influence the phenology and geographic distribution ofO. sulcatuspopulations.

The interaction of endosulfan with the Collembolan, Proisotoma minuta (Tullberg): toxicity, the effects of sub-lethal concentrations and metabolism.

An increased level of the Collembolan, Proisotoma minuta Tullberg was found in the cotton-growing areas of New South Wales, Australia. They were regularly exposed to endosulfan, a highly insecticidal compound. Toxicity, sub-lethal effects and metabolism of endosulfan were studied in P minuta that had been successfully maintained in a plaster of Paris and charcoal mixture substrate with freeze-dried yeast as a food. The 168-h LD50 values were 0.011, 0.049 and 0.055 mg liter(-1) for alpha- and beta-endosulfan and endosulfan sulfate, respectively. When P minuta were exposed to non-lethal concentrations of the endosulfans, egg production was inhibited. On recovery from the toxic effects of the endosulfans they resumed production of viable eggs. Conversion of alpha- and beta-endosulfan to endosulfan sulfate was found and the endosulfan sulfate could be further metabolized. The rate of metabolism of alpha-endosulfan was greater than that of beta-endosulfan and the product of endosulfan sulfate metabolism was not identified.

Lethal and sublethal effects of two insect growth regulators on adult Delphastus catalinae (Coleoptera: Coccinellidae), a predator of whiteflies (Homoptera: Aleyrodidae)

Pyriproxyfen, a juvenile hormone analog, and buprofezin, a chitin synthesis inhibitor, are two insect growth regulators (IGRs) considered as selective and effective insecticides for controlling whiteflies. Delphastus catalinae (Horn) is a commercially produced whitefly predator considered to be a valuable biological control agent of whiteflies, especially of Bemisia tabaci (Gennadius) ( B. argentifolii Bellows & Perring) in greenhouses. The compatibility of these two control strategies was tested by evaluating the lethal and sublethal effects resulting from ingestion of insect growth regulator (IGR) residues on treated B. tabaci eggs by adult lady beetles in the laboratory. Feeding on pyriproxyfen-treated whitefly eggs caused no significant decrease in longevity of either male or female beetles, whereas feeding on buprofezin-treated eggs reduced longevity significantly. Likewise, preoviposition period was not affected by pyriproxyfen, but was lengthened 3–6 days by buprofezin. Buprofezin reduced D. catalinae egg production and oviposition periods while a 28-day treatment with the low rate of pyriproxyfen actually increased these parameters. Both IGRs reduced D. catalinae egg fertility, especially the higher rate of pyriproxyfen and both rates of buprofezin. However, the process was largely reversed in the case of pyriproxyfen by a transfer of D. catalinae to water-treated whitefly eggs. Because D. catalinae fecundity was actually increased by 28 day exposure to the low rate of pyriproxyfen, there was no net effect on viable egg production. Thus, while both growth regulators negatively impacted D. catalinae , fewest side effects were observed with pyriproxyfen, and the worst of these, egg sterility, was reversible following removal of treated eggs.

Evaluation of egg production and quality in the Mediterranean red porgy ( Pagrus pagrus) during two consecutive spawning seasons

Egg production from two broodstocks of captive-reared red porgy ( Pagrus pagrus) was monitored for two consecutive seasons (2001 and 2002). Spawning lasted from January to April–May under water temperature between 15.8 and 19.2 °C. Spawning was mostly daily, though over the course of the two spawning seasons, the mean interval was 1.5–1.2 days spawn −1. There was a large variation in daily fecundity without a consistent trend, except for a slight peak in the middle of the spawning season. Mean (S.E.M.) annual relative fecundity ranged between 408,300 (95,800) and 442,500 (180,800) eggs kg −1 year −1. Mean fertilization success increased significantly from 36.9 (2.0)% in 2001 to 68.9 (2.5)% in 2002, resulting in mean annual viable egg production of 174,800 (87,600) and 301,500 (99,800) eggs kg −1, respectively. There were no significant differences between the 2 years in other egg quality parameters, which ranged between 74.5 and 79.3% 1-day embryo survival, 81.6–85.5% hatching success and 76.7–78.8% 5-day larval survival. Of the relations examined, fertilization % had a significantly positive correlation with 1-day embryo survival, which in turn was significantly correlated with hatching %. Larval survival was further correlated with hatching %. These data suggest that decisions on whether to proceed with the incubation of a batch of eggs and rearing of the larvae can be made within 1 day from egg collection, before much effort is invested by the hatchery. The present study presents further information on the spawning kinetics, and egg production and quality characteristics of the Mediterranean red porgy in culture, and demonstrates the suitability of this species for reproduction in captivity.

Reproductive effects of estrogenic and antiestrogenic chemicals on sheepshead minnows (Cyprinodon variegatus)

Environmental estrogens can activate genes of the reproductive system, such as vitellogenin (VTG), a precursor to egg yolk protein, by activating the estrogen receptor (ER), whereas antiestrogens can inhibit ER activation. Adult lab-reared male sheepshead minnows (Cyprinodon variegatus) were exposed to estrogenic 4-tert-octylphenol (OP) and females to antiestrogenic cadmium (Cd), and the effects on four potential indicators of impaired reproductive function were examined: VTG in F0 male blood as sign of feminization, F0 generation fecundity/fertility, embryonic development/egg hatching/survival rate of F1 generation fry, and F0 gonadal histology. Mean VTG in the control, 11.5, 33.6, and 61.1 microg/L OP male fish were 0, 10.7, 38.7, and 65.6 mg/ml postexposure and 0, 2.5, 19.4, and 30.0 mg/ml postreproduction. A significant inverse relationship between increasing VTG in male blood and reproductive success of mating groups involving these males was shown, with higher OP decreasing percent viable eggs (fertility) by approximately 60%. Histology showed increased testis anomalies and decreased spermatozoa with increasing OP exposure. No effects on F1 embryonic development, egg hatching, or fry survival rate were observed. A significant decline in percent viable egg production involving Cd-exposed females occurred only when mated with OP-exposed males, with no eggs produced by fish exposed to the highest OP and Cd concentration. A three-week field exposure near a wastewater treatment plant outfall showed no elevated VTG in male plasma, but significantly higher total egg production per female per collection day (approximately 45%) was observed at the site furthest from the outfall.

Survival and diapause egg production of the copepod Centropages hamatus raised on dinoflagellate diets

Copepods are often said to require a mixed diet to maximize their survival and reproduction potential. Copepods may be forced to feed nonselectively in food limited environments, but this does not mean they require a diverse diet. In this study, we show that the right single food item, at the right stage, can be as good or better than a mixed diet for development, survival, diapause egg production and viability. Centropages hamatus was reared on unialgal or mixed diets of five dinoflagellates: Amphidinium carterae, Prorocentrum micans, Scrippsiella trochoidea, Lingulodinium polyedra, and Gymnodinium sanguineum, ranging in size from 11×16 μm to 44×57 μm. Four experiments of 12–30 days were conducted, each testing five diets against a mixed Control diet of the four larger dinoflagellates. Algal volumes were adjusted so diets would have the same initial carbon content or cell volume at a level known to be in excess of the amount required for growth. Eggs were collected on the final 2 days of the experiments, the survivors were counted and female prosome length was measured. Diapause egg viability was measured after the eggs completed a refractory period. Nauplii had high survival on unialgal P. micans and S. trochoidea diets, but the adult females did not produce eggs. Naupliar survival was low on a unialgal diet of G. sanguineum, but the adult females had the highest rate of egg production. An optimal diet fosters growth and survival at all stages and maximizes viable egg production, to ensure high recruitment to the next generation. This can be achieved with single food items appropriate for the developmental stage. Copepods fed just two dinoflagellates, P. micans to foster juvenile growth and G. sanguineum to support final maturation and fecundity, had higher total egg production than copepods reared on the mixed diet of four dinoflagellates.

Mating and fecundity of Dermatophagoides farinae.

Studies of the life cycle of cultured Dermatophagoides farinae found that after an initial mating D. farinae females lived for 63.3+/-64.6 (SD) d after their egg production period ended (Arlian and Dippold 1996). The long period after cessation of egg production for D. farinae suggested D. farinae females could mate multiple times and produce eggs continuously for a longer period. The purpose of this study was to determine if female D. farinae could mate at least two times, and subsequently increase the production of viable eggs over a longer period of time compared to a single mating. Female D. farinae were randomly selected from thriving cultures and isolated in cages. When the females had ceased to lay eggs a male was added to the cage. Fifty-seven percent of the isolated females mated again and produced a second batch of viable eggs. In natural or culture populations, females have continuous availability of males. Therefore, in another experiment, females that emerged from the tritonymphal stages were continuously exposed to fresh males and fecundity and lengths of the reproductive and post reproductive periods were determined. These females had a 11 d longer reproductive period and produced 30.7% more eggs compared to females that only mated one time after they emerged from the tritonymphal stage. However, the post reproductive period was still long (58.6+/-11.4 [SE] d) the significance of which is not clear. In conclusion, this study revealed that D. farinae females are capable of more than one successful mating that results in increased egg production compared to that of a single mating. It is likely that females mate multiple times in natural and culture populations. It was observed that females actively attract males during the reproductive period but not afterward even though she continues to live a long time.

Spatial variation in abundance, size composition and viable egg production of spawning cod (Gadus morhua L.) in Icelandic waters

Changes in geographical location of spawning and/or in spatial abundance of spawners may influence offspring survival. In Iceland, the spatial dynamics of spawning cod (Gadus morhua L.) are complicated due to unequal distribution of size classes on the main spawning grounds. Information on abundance, age, and size distributions during peak spawning, potential fecundity, egg size, and estimated larval viabilities were used to contrast the reproductive potential of three adjacent spawning areas within the main spawning ground of cod in the Icelandic waters. The three areas differed with respect to age and size distribution, abundance, mean production per female and an index of total egg production. Larger and faster growing cod spawned closer to the coast (area 1). Smaller cod spawned in deeper water out on Selvogsbanki (area 2), and the smallest and youngest cod tended to spawn along the continental edge (area 3). Relative abundance was higher in area 2 than in areas 1 and 3 (640, 153, and 334 kg/net, respectively). Mean production of eggs per female was highest in area 1, while the index of total egg production was highest in area 2. The estimates of viable egg production did not change the general results. Estimates of the proportion of viable eggs produced were slightly higher in area 1 than in areas 2 and 3. However, the influence of the relative abundance of spawners in the different areas overrode any trends due to higher mean production of viable eggs. The results demonstrate that egg production, based on abundance and size and age composition of spawning cod, may vary extensively among different spawning areas. Such information, in conjunction with documentation of spatial and temporal variation in oceanic and environmental conditions, may provide an important contribution towards the understanding of recruitment processes necessary for management of commercially important fish species.

Life-cycle toxicity of bis(tributyltin) oxide to the sheepshead minnow (Cyprinodon variegatus).

The effects of tributyltin (TBT) to the life cycle of the estuarine fish Cyprinodon variegatus were examined in a 180-day flow-through exposure. The study was initiated with embryos less than 24 h postfertilization and monitored through hatch, maturation, growth, and reproduction under continuous exposure to mean measured TBT concentrations of 5.4, 3.2, 1.3, 0.66, and 0.41 microg TBT/L. Progeny isolated at the onset of reproduction by the parental generation (F0) were monitored for survival as embryos, survival as fry/juveniles, and growth 30 days postisolation. TBT, at a concentration of 5.4 microg/L, significantly reduced embryo survival of the F0 generation sheepshead minnows. By day 145 of the exposure, significant effects to the survival of this generation increased and included all test concentrations >/=0.66 microg/L. Survival of 0.66 microg/L was reduced 59% relative to control survival by termination of the F0 generation. Growth of F0 generation organisms as measured by standard length was significantly reduced only on day 90 at 3.2 microg/L, however no significant reductions of wet or dry weight related to treatment concentration were detected. Due to complete mortality of organisms exposed to 5.4 microg/L by study day 7, effects to fecundity and progeny were monitored at measured concentrations of 3.2, 1.3, 0.66, and 0.41 microg TBT/L. Fecundity, as measured by the production of viable eggs produced per female per day, was unaffected by any of the test treatments. All F1 generation embryos isolated from treatment chambers into 3.2 microg/L died. Survival, standard length, wet and dry weight of the F1 generation at the remaining treatment concentrations were unaffected. The results of this study indicate that exposure to TBT reduced survival of the F0 generation sheepshead minnow and establishes the lowest observed effect concentration (LOEC) as 0.66 microg TBT/L, and the no observed effect concentration (NOEC) as 0.41 microg TBT/L for this species.http://link.springer-ny. com/link/service/journals/00244/bibs/37n2p258.html

Induction of spawning in gilthead seabream, Sparus aurata L., by a long-acting GnRH agonist and its effects on egg quality and daily timing of spawning

Ovulation and spawning were induced in gilthead seabream, Sparus aurata L., which had failed to spawn spontaneously after thermal manipulations, using a long-acting commercial preparation of leuprolide acetate, an agonist of gonadotropin releasing hormone (GnRHa), in order to study the effects of this treatment on spawning periodicity, the timing of spawning, daily egg production and embryonic viability. Grouped and single females bearing yolky follicles were implanted once with 20, 40 or 80 μg kg −1 (body weight) of GnRHa encapsulated in a biodegradable copolymer, copoly( dl-lactic/glycolic acid ratio of 3:1). All treated females started to spawn after 48 h and about 40% of the eggs were laid during the initial 10-day period with daily peaks of 10 5 eggs kg −1. The mean daily production of viable eggs ranged between 71–288.10 2 eggs kg −1. Embryonic viability was equivalent to that of control fish which were induced to spawn with a rise in water temperature. There was, however, a significantly ( P < 0.01) higher egg production in the GnRHa-treated fish. While egg laying occurred regularly at dawn in controls, the long-acting GnRHa tended to shorten the normal 24-h ovulatory cycle of seabream, gradually shifting spawning from dawn to sunset. In tanks with single females, sudden spawning readjustments were observed from sunset to dawn through short 12-h ovulatory cycles. Interestingly, spawning of single females with two males resulted in a greater percentage of non-fertilized eggs in comparison to groups of spawning females maintained with a similar ratio of males, presumably as a result of territorial competition when few males try to occupy the same spawning tank.

Nurse cell polytene chromosomes of Drosophila melanogaster otu mutants: morphological changes accompanying interallelic complementation and position effect variegation.

Combinations of certain mutant alleles of the ovarian tumor gene permit the production of viable eggs. Two alleles that behave in this way are otu7 and otu11. Females homozygous for either allele are sterile, and their ovarian nurse cells (NC) contain giant polytene chromosomes of various morphologies. Fertile flies (otu+/otu+, otu+/otu7, otu+/otu11) have endopolyploid nurse cells with typical dispersed chromosomes. Fertile hybrids (otu7/otu11) produce large numbers of polytene chromosomes comparable to, and often larger than, classic salivary gland (SG) chromosomes. Therefore, these otu hybrids provide a unique system for studying, at the chromosomal level, the activation and expression of genes functioning during oogenesis. The otu gene encodes a long and a short isoform. The normal long isoform appears to be responsible for the dispersion of chromosomes during the endomitolic DNA replications occurring in ovarian NCs. The genetic inactivation of euchromatic genes placed next to pericentric heterochromatin by a chromosomal rearrangement is accompanied by the compaction of corresponding chromosome regions. A comparative study of the manifestation of position-effect variegation for the polytene chromosomes of SG cells and NCs was made using the Dp(1;1)pn 2b and Dp(1;f)1337 rearrangements. The percentage frequencies of block formation in the SG and NC nuclei for Dp(1;1)pn 2b rearrangement were 92.6% vs. 15.8%, respectively; for Dp(1;f) 1337, these values were 56.8% vs. 9.7%. Therefore heterochromatin belonging to germ line chromosomes is in a configuration that is far less likely to inactivate inserted segments of euchromatin than is heterochromatin from somatic chromosomes.

The diatom Thalassiosira rotula affects reproductive success in the copepod Acartia clausi

Fecundity, egg viability and fecal pellet production are reported for Acartia clausi females collected in the Bay of Naples, Italy, from April to October 1992 and fed either with a diatom (Thalassiosira rotula) or dinoflagellate (Prorocentrum minimum) diet, at food saturated conditions. The diatom diet significantly reduced both egg and fecal pellet production as well as hatching success. Blockage of egg development occurred with both axenic and non-axenic cultures of T. rotula, suggesting that inhibitors were provided by the diatoms and not by the bacteria associated with diatom cultures. Low hatching success was also artificially induced by exposing newly spawned A. clausi eggs to high concentrations of diatom extracts, indicating the presence of deleterious, inhibitory compounds blocking copepod embryogenesis. Fecundity and hatching success diminished significantly with female age. In contrast, female longevity was not significantly modified by food type. The presence of males did not significantly alter fecundity or egg viability. Females continued to produce viable eggs throughout the period of incubation, with and without males, in both food conditions, indicating that remating is infrequent and not necessary to sustain viable egg production in this species. The succession in low and high population densities may therefore be the outcome of variations in survival rates of eggs, rather than reproductive protential perse; such variations may strongly depend on the adult copepod diet.

UTILIZATION AND DEGREE OF DEPLETION OF EXOGENOUS SPERM IN THREE HERMAPHRODITIC SEA HARES OF THE GENUS APLYSIA (GASTROPODA: OPISTHOBRANCHIA)

Two series of experiments were conducted to examine the utilization of exogenous sperm and their degree of depletion in three hermaphroditic sea hares, Aplysia kurodai Baba, 1937, A. Juliana Quoy & Gaunard, 1832, and A. parvula Guilding in MOrch, 1863. The first series of experiments was designed to determine whether one mating is enough for female partners to receive sufficient sperm to fertilize at least one egg mass. For this purpose, isolated individuals were mated as females once with conspecific individuals and the viability of their subsequent eggs was examined. When successfully inseminated, individuals of all the three species received enough sperm to fertilize at least one egg mass, and they continued to lay 3.6–8.5 viable egg masses. However, 10–36% of the matings by these sea hares did not result in any viable egg production by the female partner, indicating that these matings did not involve sperm transfer Such matings without sperm transfer tended to be shorter than matings with successful sperm transfer The second experimental series was conducted to examine whether sperm depletion actually occurs or not in field-caught adults. For this purpose, adult individuals caught in the field were allowed to lay eggs under isolated conditions without mating All the individuals of A. kurodai and A. juliana stored enough sperm to fertilize at least one egg mass. However, in A. parvula, 23–33% of individuals laid egg masses containing non-viable eggs at their first spawning after isolation, indicating that these individuals were depleted in exogenous sperm

Indoor husbandry of the panther chameleonChamaeleo [Furcifer] pardalis: Effects of dietary vitamins A and D and ultraviolet irradiation on pathology and life-history traits

To assess the importance of diet and light for indoor maintenance, hatchling panther chameleons were reared for 1 year on crickets fed diets that differed in vitamin concentrations and in different light environments. Dietary transfer of vitamins from the cricket diet to the lizards via the crickets was quantified, as was UV irradiance. There was a statistically significant dietary enhancement of growth by both vitamins on males. UV-A irradiation significantly suppressed growth of females. Low vitamin A shortened life span and resulted in a number of gross and histological pathologies. Hepatocellular lipidosis, indicating a possible toxicosis, occurred with all diets and light treatments. Higher vitamin A resulted in mild soft-tissue mineralization, and high vitamin D shortened the life span of females. Low vitamin A drastically reduced reproduction in both sexes. The intermediate levels of dietary vitamins resulted in the best production of viable eggs by females. However, without high UV-B irradiation, all viable eggs died at term and contained different vitamin levels than hatching eggs from wild-caught females. Baseline levels of egg calcium are given for hatching eggs from wild-caught females. Modifications in current husbandry procedures are recommended. © 1996 Wiley-Liss, Inc.

Egg viability in the copepod Temora stylifera

Estimates of production rate and viability of eggs are reported for Temora stylifera collected in the Bay of Naples (Italy). Complementary observations on rates of fecal pellet and spermatophore production and female longevity were also conducted during the incubations. In situ egg viability was highly variable during the 2 yr of observation, with mean monthly values of &lt;80% of total egg production. Under experimental food‐saturated conditions, the nature and hatching success of eggs were modified depending on type of food. With a dinoflagellate diet (Prorocentrum minimum), the responses of copepods were characterized by maximum production of viable eggs, high female longevity in the presence or absence of males, and low rates of fecal pellet production. The opposite was true with a diatom diet (Thalassiosira rotula), except fecal pellets were produced at a higher rate, showing indirectly that this algae was neither properly assimilated nor transformed into production. Total and mean daily egg production were more or less the same with the two diets, indicating that under poorer food conditions copepods can maximize total egg production but not viability.

SUCROSE INGESTION BY ZEIRAPHERA CANADENSIS MUT. &amp; FREE. (LEPIDOPTERA: TORTRICIDAE) INCREASES LONGEVITY AND LIFETIME FECUNDITY BUT NOT OVIPOSITION RATE

AbstractIn the laboratory, the longevity and fecundity of female Zeiraphera canadensis Mut. &amp; Free. (Lepidoptera: Tortricidae) given access to a 10% sucrose solution and water was greater than that of females provided only water. The presence or absence of sucrose did not affect oviposition rate during the first 10 days post-emergence, after which most females denied sucrose died. The enhanced fecundity of sucrose-fed females was due to their increased longevity and, hence, longer oviposition period. Greater longevity, combined with a decrease in oviposition rate and egg viability with age, resulted in a lower average lifetime oviposition rate and percentage viable egg production for females provided sucrose. Although carbohydrate ingestion resulted in increased fecundity and longevity in the laboratory, its effect in nature may be minimal because Z. canadensis usually does not live more than 10 days under field conditions.

Mating, Longevity, Fecundity, and Egg Fertility of Chilo partellus (Lepidoptera: Pyralidae): Effects of Delayed or Successive Matings and Their Relevance to Pheromonal Control Methods

Male and female Chilo partellus (Swinhoe) were paired on days 0–7 after eclosion to determine the effect of aging on mating ability, and the effects of delayed mating on longevity, preoviposition and oviposition periods, fecundity, and egg fertility. When the moths were of equal age, 58% mated on the night of eclosion, 80–85% 1–2 d after, and then significantly fewer. Mating ability of the males remained high for 5 d and then declined significantly, whereas in females it decreased progressively starting 2 d after eclosion. Female longevity and the preoviposition period both increased with increasing age at mating, but the oviposition period decreased in late-mated females. Mean fecundity and egg fertility of females mated 1 and 4 d after eclosion were 538.2 and 91% and 345.4 and 51%, respectively. Both were reduced significantly when mating was delayed beyond 4 dafter eclosion. A 4-d delay in mating could cause a 67% reduction in viable egg production. Given the opportunity, males copulated an average of 4.6 times, while females usually mated once. The spermatophores transferred during the first six matings by the male were equally effective in producing fertile eggs. These observations suggest that mass trapping of males using pheromone traps as a control method for C. partellus would not be feasible. However, delaying and disrupting mating by permeating the field with female sex pheromone would be a more effective behavioral control strategy.

Female sex pheromones of Chilo spp. (Lepidoptera: Pyralidae) and their development in pest control applications

Female sex pheromone components have been identified for seven species of Chilo, pests of cereals and sugar-cane. Synthetic pheromone blends for C. suppressalis, C. sacchariphagus, C. sacchariphagus indicus, C. auricilius and C. zacconius have shown satisfactory attractiveness to male moths in the field. Blends for C. partellus and C. infuscatellus seem to be incomplete. Pheromones and related compounds have been investigated for control of C. suppressalis by mating disruption in the Philippines, Japan, Spain and Korea. These studies have shown not only trap catch reduction, but also reduced viable egg production in field cages and effective control of damage by this pest on areas up to 60 ha. Initial studies have been carried out on control of C. sacchariphagus by mating disruption in Mauritius, and both the pheromone and an inhibitor have been shown to cause trap catch reduction of C. auricilius in India. Attempts have been made to control C. sacchariphagus indicus by mass trapping in India.

Single and multiple worm infections of Echinostoma caproni (Trematoda) in the golden hamster

Six of 10 hamsters fed a single metacercarial cyst of Echinostoma caproni (single-worm infections) and 13 of 19 hamsters fed either 2 or 5 cysts (multiple-worm infections) were infected with adult echinostomes at necropsy 22 days post-infection. Considerable histopathological changes to the small intestine occurred in hamsters carrying single-worm infections. There were no differences in either mean length, width or wet weight of echinostomes in single- versus multiple-worm infections. The mean number of eggs/worm from single-worm infections (525) was significantly greater than that from multiple-worm infections (288). The average percentage of fully developed miracidia/worm from single worms (94%) was similar to that from worms in multiple infections (92-95%). Single worms of E. caproni were capable of self-fertilization and production of viable eggs. Miracidia derived from single worms were as capable of infecting laboratory-reared Biomphalaria glabrata and producing patent rediae as were those from multiple infections.

Differential viability of eggs laid by queens in polygyne colonies of the fire ant, Solenopsis invicta

The viability of eggs laid by individual functional queens from polygyne colonies of the fire ant, Solenopsis invicta Buren, was examined by staining for chromatin. In isolation units held in the laboratory inseminated queens laid nearly 100% viable eggs, compared to <10% for uninseminated queens. Experiments in which the quantity of brood was manipulated demonstrated that the number of brood and workers present has little, if any, effect on the ability of a queen's eggs to form embryos, in contrast to the stimulatory effect of larvae on oviposition rate. In field colonies, although there was considerable variability among queens, inseminated queens laid a significantly greater proportion of viable eggs than did uninseminated queens. Inseminated queens taken directly from polygyne colonies in the field laid a smaller proportion of viable eggs than those maintained individually for several weeks in the laboratory, suggesting that there is mutual inhibition among cohabiting inseminated queens which affects viable egg production. Among queens taken from the field, there was no significant correlation between the proportion of viable eggs laid and queen weight, a reliable indicator of oviposition rate. Thus caution should be exercised in equating relative rates of egg production with reproductive success in studies of reproductive roles in social insect colonies.