Egg distribution patterns in the almond seed wasp,Eurytoma amygdali

The egg distribution patterns ofEurytoma amygdali Enderlein (Hymenoptera, Eurytomidae), which oviposits singly in green, developing almonds, were studied in the laboratory and in the field. In the laboratory, individual females were caged with a number of almonds and the eggs deposited in each fruit were counted. In the field, eggs were censused in almonds of different varieties at regular intervals, over four seasons (1988–91). In the susceptible ‘Retsou’ variety, eggs were uniformly distributed among fruits, both in the laboratory and in the field, as long as the mean number of eggs per almond was ≤2.5. When the mean number of eggs per almond was higher the egg distributions were random. This suggests that, up to a certain level of infestation, females were able to assess egg load of fruits and oviposit in the less infested ones. The main factor enabling the females to discriminate and select the less infested almonds for oviposition is probably a host-marking pheromone. In 1990, the same patterns of egg distribution were observed in samples taken from 5 other almond varieties that are not as susceptible as Retsou and have thicker pericarp and harder endocarp. In 1991 however, when fruits developed more rapidly than in 1990, egg distributions in 3 of these 5 varieties (Truoito, Ai, and Marcona) were not uniform. Although the mean number of eggs per fruit was low (1.2–2.0), many fruits of these varieties contained no eggs. This suggests that, in some less susceptible varieties, egg distribution might also be affected by certain fruit parameters, unfavourable for oviposition, related to the pericarp thickness and endocarp hardness.     

Seasonal susceptibility of 'Bartlett' pears to codling moth (Lepidoptera: Tortricidae) infestation and notes on diapause induction

Seasonal susceptibility of 'Bartlett' pear, Pyrus communis L., to codling moth, Cydia pomonella (L.), infestation, successful completion of larval development after infestation, and the induction of C. pomonella diapause was studied from 1992 through 1995. The seasonal variation in C. pomonella infestation and larval survival were effected by changes in fruit maturity. In late May through mid-June, pears were hard and were not as successfully infested by C. pomonella and produced less larvae compared with fruit later in the season. In late June to mid-July, pears became more suitable for infestation and a greater percentage of the larvae completed their development. In late July through mid-August, pears were susceptible to infestation, but the larvae were less likely to successfully complete development than in the late June to mid-July period due to pear tissue breakdown. From mid-August through September, pears are unsuitable for infestation, and few larvae were produced. When fruit were infested with neonate larvae in late May and mature larvae emerged from the fruit in July, a low percentage of the larvae entered diapause. However, when fruit were infested with neonate larvae in early July and mature larvae emerged from the fruit in early August, the majority of the larvae entered diapause. When fruit were infested with neonate larvae in late July through September and mature larvae emerged from the fruit after mid-August, nearly all C. pomonella larvae had entered diapause.     

Spatial distribution and hatching of overwintered eggs of a fish ectoparasite, Argulus coregoni (Crustacea: Branchiura).

The habitat distribution of overwintered eggs, which were found to be the only source of spring recruitment of Argulus coregoni Thorell, was studied at a commercial fish farm in Central Finland. The frequency of occurrence of egg clutches in the deep parts of the canals and ponds was 50 to 80% and the percentage cover of the surface of stones with egg clutches was 1.7 to 6.4%, while in the shallow parts these values were 8 to 27% and 0.1 to 0.3%, respectively. A greater proportion of empty egg-shells was observed in shallow water in the mid-May, suggesting an earlier hatching there stimulated by the increased temperature and higher illumination. Under laboratory conditions, only elevated UV illumination, but not diurnally fluctuating temperature, significantly accelerated hatching. Normally overwintered eggs produced a pronounced peak of hatched larvae at the end of May and hatching continued at a much slower rate throughout the summer. Eggs that overwintered twice, first normally and then for a second time buried under sediments, were exposed to the same laboratory conditions simultaneously with normally overwintered eggs, but their hatching was delayed until August. The hatching rate was low, but markedly increased in December.     

Hull split date and shell seal in relation to navel orangeworm (Lepidoptera: Pyralidae) infestation of almonds

Hull split date, shell seal, and navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), infestation data for 19 varieties of almonds, Prunus dulcis (Mill.) D.A. Webb, were analyzed to determine the relationship of shell seal and hull split date on A. transitella infestation. Data for all varieties were collected from three University of California regional almond variety trials from 2003 to 2005, with a total of 8,550 nuts evaluated. A significant negative relationship was found between percentage of shell seal and percentage of navel orangeworm infestation, with lower percentage of shell seal correlating to higher percentage of infestation. Similarly, hull split date was negatively correlated with percentage of infestation, with later splitting varieties trending toward lower percentage of infestation. Although there are outlying varieties, hull split and shell seal are indeed significant components in varietal differences in almond navel orangeworm infestation. Understanding such factors gives insight into both the predictive value of almond characteristics related to navel orangeworm damage as well as other potential indicators.     

Levels of natural resistance to Boophilus microplus (Acari: Ixodidae) in Carora breed bulls.

Boophilus microplus infestation is one of the most serious limitations to cattle industry in tropical regions, even though bovines show natural resistance to ticks. This resistance was evaluated in Cross-bred Carora Bulls (CCB) a tropicalized dairy breed from Venezuela. Seven CCB were experimentally infested with B. microplus larvae, "Mozo" strain, they were considered tick-naive because they had never been infested with ticks. The mean inoculum size applied on each bull was 6,477 larvae. After life cycle was completed adult female body weight (BW), egg mass weight (EW), egg hatching rate (%EH), and reproductive index (RI) were recorded. Results revealed a high variability in the levels of resistance to B. microplus. Thus, one animal showed greater resistance (Dunnett, p < 0.05) for the analyzed parameters in contrast with three non-resistant bulls. The others had moderate resistance. The trait "resistance" should be included together with other traits often used in genetic selection of cattle.     

The copepod Centropages abdominalis as a carrier of the stalked ciliate Zoothamnium

Adult specimens of the calanoid copepod Centropages abdominalis collected from February through April 1986 in Shinhamako, a saline lake connected to Tokyo Bay, were heavily infested with the stalked ciliate Zoothamnium. The number of copepods and those infested varied during the infestation period; in February when the copepod population was large, the incidence of infestation was low, whereas in March when the copepod population was small, copepods infested with Zoothamnium were proportionally more abundant. Numerical variations of infested copepods may correspond to changes in the Zoothamnium population. No specimens of Acartia omorii, which coexists with C. abdominalis, were infested in 1986, although a small number of A. omorii were infested with peritrich ciliates in 1985. Some shrimp larvae were also covered with the same peritrichs as copepods. Nevertheless, as a whole, the relationship between the phoront and its carrier seems to be specific. The highest incidence of infested copepods was approximately 30% similar to that in 1985. The sex ratio of C. abdominalis changed on each sampling date but in general females were more numerous than males. The percentage of infested males was higher than that of infested females, suggesting that the former can be attached to more easily than the latter.     

Seasonality and infestation pattern of epibiosis in the beach mysid Archaeomysis articulata

Seasonal variation and the infestation pattern of epibiosis in the beach mysid Archaeomysis articulata Hanamura, 1997, were studied based on intertidal samples over 1 year on a sandy beach in Ishikari Bay, northern Japan. The mysid-peritrich ciliate association was a year-round phenomenon in Ishikari Bay and the prevalence of infestation varied from 49 to 100% (average: 92%) during the investigation; no significant seasonal trend was noted. Incidence of infestation in smaller mysids (<5 mm) was significantly lower than in larger mysids (>5 mm). The number of ciliates carried by adult, mostly ovigerous, females was greater than that by adult males. Last stage embryonic larvae were occasionally infested by ciliates, but early stage larvae were absolutely free from epibionts. Dense infestation of epibionts was not correlated with the abundance of mysids, hence the impact of ciliates on natural populations of mysids is assumed to be insignificant.     

Almond seed wasp (Hymenoptera: Eurytomidae) sex pheromone: effect of trap type, trap position, blend ratio and time of the day on male attraction

Field trials were carried out in order to evaluate some of the factors affecting male response of the almond seed wasp, Eurytoma amygdali Enderlein, to traps baited with the alkadienes (Z,Z)-6,9-tricosadiene and (Z,Z)-6,9-pentacosadiene, the male attractant of this species. The trials were conducted in Latomia, Microthivae, Kanalia and Sykourion (Thessaly, Central Greece) during the 2004 growing season. In all regions, captures in traps baited with a 7:3 ratio of the above blend significantly and positively correlated with male emergence from infested almonds that had been placed in cages in the experimental fields. Traps baited with the 7:3 pheromone ratio were significantly more effective in capturing males than traps baited with the 1:1 ratio, supporting the hypothesis that (Z,Z)-6,9-tricosadiene is the main component of this attractant. Of four trap types tested, Rebel and Lasiotraps attracted significantly more males than Delta and Funnel traps. Height had no effect on trap efficiency; however, males were captured earlier in the day in traps placed 2.3 m above grown than in traps placed 1.3 m above grown. Most male activity was recorded between 10 and 12 h, but captures were continuously recorded during the entire monitoring interval from 6 to 17 h.     

Fish hatching strategies: a review

The paper presents differences in the distribution of hatching gland cells, and the location of egg envelope digestion, the significance of hatching movements, and the ways larvae escape from egg envelopes. A review of the literature on the hatching orientation of 34 fish species is compared. No correlation was seen between hatching orientation and egg diameter or newly hatched larva length, nor newly hatched larvae length ratio to egg diameter. Photographs of twelve freshwater species present the moment of hatching either head first or tail first. Some differences were shown in swelling between eggs incubated in commercial hatchery and developed in natural conditions, as well as possible effect of these differences on hatching.     

Infestation and seasonal activity of Ixodes vespertilionis Koch, 1844 (Acari: Ixodidae) on the Maghreb mouse‐eared bat,Myotis punicus Felten, 1977, in northeastern Algeria

Infestation of Ixodes vespertilionis Koch, 1844 on Myotis punicus Felten, 1977 from two sites (Trios Tunnel and Sidi Trad cave) in northeastern Algeria was studied. An overall infestation of 41.4% for all stages was found among bats collected from both sites. By stage, a total of eight females, 70 nymphs, and 107 larvae were recovered from both populations. The number of females recovered per bat at Sidi Trad ranged from 0‐1, for nymphs 0‐2, and for larvae 0‐2. While no female ticks were collected at Trios Tunnel, the number of nymphs ranged from 0‐2 and for larvae 0‐2. At Trios Tunnel, the number of nymphs was significantly higher during April and June but not for July and September. On the other hand, the number of larvae increased from July to November, while at Sidi Trad cave, female ticks were recovered during April and May and then disappeared until the end of the study period. Significant differences were noted during all the months when compared with all stages. Nymphs infested bats significantly during April and May, declined in June and July, and then became steady until October. Larvae peaked in July, with low frequency in April, and then fluctuated from August to November.     

颗粒体病毒在小菜蛾种群中的垂直传播方式的初步观察

在室内观察了小菜蛾颗粒体病毒PlutellaxylostellaGranulosisVirus(RxGV)在小菜蛾种群水平上可能的垂直传播途径。结果表明 :(1 )上代小菜蛾Plutellaxylostella(L .)幼虫期饲毒不能将小菜蛾颗粒体病垂直传递到下代 ;(2 )取食病毒的雌蛾产的卵所孵化的幼虫中 ,没病毒感染出现 ,说明病毒不能经小菜蛾成虫体内传播到下一代。 (3 )用小菜蛾颗粒体病毒处理卵卡时 ,其初孵幼虫有少量被病毒感染死亡 ,浓度高时感染率也较高 ,但感染率均在 1 0 %以下 ,说明小菜蛾颗粒体病毒能经卵表垂直传递给下代 ,但传递效率不高。但当用病毒处理叶片上的卵时 ,初孵幼虫死亡率高达 77 73 % ,而且孵化出的幼虫大多数染病且死于 3龄以前 ,因此田间病毒的施用时间可提早到卵高峰期。     

Effects of temperature experienced during embryonic development on biomass and C and N composition at hatching in Palaemon serratus (Pennant, 1777)

In decapod crustaceans, the conditions experienced during embryonic development trigger phenotypic plasticity of the larvae at hatching. The objective of this study was to test the effects of temperature during embryonic development of Palaemon serratus on the phenotypic plasticity of hatching larvae. We incubated egg-bearing females from eggs laying to hatching at four temperatures (10, 15, 18 and 20°C). Weight, carbon and nitrogen contents were measured on newly laid eggs and on freshly hatched larvae. The duration of embryonic development was negatively correlated with incubation temperature. At 20°C, all females abandoned their eggs during development. Incubation temperature had no effect on the weight and the percentage of N of the larvae at hatching, while it did affect their percentage of C and their C/N ratio. Embryos incubated at 10°C seemed to produce larvae with fewer lipid reserves than those incubated at 15 and 18°C. They probably overconsumed their lipid reserves to compensate for the metabolic losses due to the low temperature. These results provide information on the link between maternal investment per egg and larval development in P. serratus.     

Role of egg density on establishment and plant-to-plant movement by western corn rootworm larvae (Coleoptera: Chrysomelidae)

The effect of egg density on establishment and dispersal of larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was evaluated in a 3-yr field study. Implications of these data for resistance management plans for Bt crops are discussed. Viable egg levels of 100, 200, 400, 800, and 1600 eggs per infested plant were evaluated in 2000, 2001, and 2002. A 3200 viable egg level was also tested in 2001 and 2002. All eggs were infested on one plant per subplot in a field that was planted to soybean, Glycine max (L.), in the previous year. For each subplot, the infested plant, three plants down the row, the closest plant in the adjacent row of the plot, and a control plant at least 1.5 m from any infested plant (six plants total) were sampled. In 2000, there were five sample dates between egg hatch and pupation, and in 2001 and 2002, there were six sample dates. On each sample date, four replications of each egg density were sampled for both larval recovery and plant damage. Initial establishment on a corn plant seemed to not be density-dependent because a similar percentage of larvae was recovered from all infestation rates. Plant damage and, secondarily, subsequent postestablishment larval movement were density-dependent. Very little damage and postestablishment movement occurred at lower infestation levels, but significant damage and movement occurred at higher infestation rates. Movement generally occurred at a similar time as significant plant damage and not at initial establishment, so timing of movement seemed to be motivated by available food resources rather than crowding. At the highest infestation level in 2001, significant movement three plants down the row and across the 0.76 m row was detected, perhaps impacting refuge strategies for transgenic corn.     

The apple sawfly, Hoplocampa testudinea: egg development and forecasting of egg hatch

The effect of temperature on egg development of the apple sawfly Hoplocampa testudinea Klug was studied under controlled conditions. Based on a linear model describing the relationship between temperature and developmental rates a thermal threshold of 6.9 °C and a thermal constant of 85 day-degrees were established. The experimental results were used to expand and parameterise an existing phenology model to include egg development and hatching of first instar larvae. The model thus became a valuable forecasting tool not only for adult emergence and the optimal monitoring period but also for egg hatch and the best timing of control measures against first instar larvae. The model was validated by comparing predictions with independent observations on egg-laying and subsequent hatching of first instar larvae under semi-field conditions.     

Interspecific and intraspecific variations in egg hatching for British populations of the stoneflies Siphonoperla torrentium and Chloroperia tripunctata (Plecoptera: Chloroperiidae)

SUMMARY 1. The objective was to compare variations in egg hatching between the two species (interspecific variations) and between populations of the same species (intraspecific variations). There were significant interspecific, but not intraspecific, differences in female size, adult life-span, egg production, hatching success, incubation periods and hatching periods.
2. The optimum temperature for hatching success within the range 3.8–22.1°C in the laboratory and the range over which at least 50% of the eggs hatched were lower for Chloroperia tripunctata (Scopoli) (8.5°C, 4.2–17.3°C) than for Siphonoperla torrentium (Pictet) (12.8°C, 6.1–19.4°C). Few eggs hatched at 22.r°C.
3. The relationship between incubation period (d days) and water temperature (T°C) was given by: d=1219/T^1.368 for S. torrentium , d=253/T^0.459 for C. tripunctata . Both equations successfully predicted incubation periods for eggs placed in a stream. The period over which eggs hatched was much longer for C. tripunctata than for S. torrentium at all temperatures.
4. The shorter incubation period (at r>5.6°C) and shorter hatching period for S. torrentium ensure that larvae of this species are already growing when eggs of C. tripunctata start to hatch, but the prolonged hatching period of the latter species ensures a long period of larval recruitment to the population. These differences in egg hatching may reduce competition between the two closely-related species.     

Population ecology of the commensal chironomid Epoicocladius flavens on its mayfly host Ephemera danica

SUMMARY. 1. Epoicocladius flavens (Diptera: Chironomidae) has a 1-year life cycle in the River Tud in eastern England. Pupation and adult emergence occurred from the end of May until the beginning of September. Larval growth was rapid during the summer but thereafter almost ceased until the following April.1 Unlike other chironomids, the population density of E. flavens was very stable and remained at around 1000m ⁻² all through the year.
2. Ephemera danica (Ephemeroptera: Ephemeridae), the host of E. flavens , has a 2-year life cycle. The proportion infested was about 90% for the older host year-class and less than 30% for the younger year-class from autumn until the following summer. A rapid increase in infestation occurred during the summer as a result of hatching of the E. flavens eggs. Of those infested, the older year-class hosts harboured two or three larvae, on average, whereas the younger ones had only one.
3. When host year-classes were treated separately, the frequency distribution of the number of E. flavens per host each month did not depart significantly from a Poisson distribution. Younger instars departed from a Poisson distribution more frequently than older instars.
4. The majority of E. flavens larvae attached to the gills of their hosts. As the instars progressed, increasing proportions were found on the thorax, legs and tails. The thorax was the preferred site for fourth instar larvae.
5. Enhanced chance of survival, rather than the supply of detrital food particles which collect on the host's body, is considered as an important benefit to accrue to E. flavens from this commensalism.     

Pathogenicity of entomopathogenic hyphomycetes, Paecilomyces fumoso-roseus and Nomuraea rileyi, to eggs of noctuids, Mamestra brassicae and Spodoptera littoralis

Bioassays were conducted to determine the susceptibility of egg masses of Mamestra brassicae and Spodoptera littoralis to different spore doses of Paecilomyces fumoso-roseus and Nomuraea rileyi at 20° and 25°C. P. fumoso-roseus was highly virulent against eggs, whereas N. rileyi provoked only a deferred mortality of larvae hatched from treated eggs. Nevertheless, larval mortality of S. littoralis caused by N. rileyi at 25°C was more effective after first-instar larval contamination than after egg mass treatment. The duration of the egg stage could explain differences of susceptibility between the two noctuids at 25°C. Scanning electron microscopical observations suggested two ways of contamination of newly hatched larvae. First, fungal germinations on the chorion surface suggested that newly hatched larvae might be infected by penetration of the egg integument before hatching. Second, conidia on the egg cuticle could be an entomopathogenic inoculum for newly emerging larvae which fed upon chorions. Results showed that pathogenicity of Hyphomycetes to noctuid eggs might be a promising area of investigation for biological control.     

平卧川牛漆甾酮对小菜蛾生长发育的影响(英文)

平卧川牛漆甾酮是紫背金盘中的主要植物蜕皮甾类 ,在筋骨草属植物中普遍存在。试验结果表明 ,用 5 0mg L平卧川牛漆甾酮处理小菜蛾卵 ,其孵化受到抑制 ,总孵化率为 94.7% ,显著低于对照的 1 0 0 %孵化。平卧川牛漆甾酮对幼虫具有弱的毒杀活性和良好的拒食活性 ,且与浓度相关。小菜蛾的生长发育也受平卧川牛漆甾酮的影响。用高于 5 0mg L浓度处理幼虫 ,其生长受抑及蛾的产卵量下降 ,而较低浓度处理则有利于幼虫生长 ,卵量提高。这种双重作用可能是由于平卧川牛漆甾酮的激素活性和拒食活性的作用结果 ,后者导致昆虫营养不良。处理幼虫后 ,试虫的化蛹和羽化受阻。小菜蛾对平卧川牛漆甾酮比 2 0 羟基蜕皮酮更敏感。     

Control of the flat-headed root borer <Emphasis Type="Italic">Capnodis tenebrionis</Emphasis> (Linné) (Coleoptera: Buprestidae) with the entomopathogenic nematode <Emphasis Type="Italic">Steinernema carpocapsae</Emphasis> (Weiser) (Nematoda: Steinernematidae) in a chitosan formulation in apricot orchards

Entomopathogenic nematodes Steinernema carpocapsae were applied in a chitosan formulation (Biorend R^®) to control the flat-headed rootborer Capnodis tenebrionis (Coleoptera: Buprestidae) in 5 field trials in the province of Valencia, Spain. Application was performed during spring and summer into the soil around apricot trees at densities of 1 and 1.5 million infective dauer juveniles per tree through drip irrigation, injection or by a drench. For evaluation of the control effect the roots of 106 trees were excavated, the cortex removed and living and dead insects were sampled. Dead larvae were dissected and checked for nematode infestation. Control of C. tenebrionis larvae was between 75% and 90%. No influence of the application method, nematode density or time of application on the control effect was recorded. Recovery of the infested trees was observed already in the season following nematode application. Due to the two year life cycle of the insect with egg laying from May to August, applications during spring and autumn are recommended.     

Reproductive biology and morphology of eggs and larvae of Stiphodon percnopterygionus (Gobiidae: Sicydiinae) collected from Okinawa Island

Reproductive biology and morphology of eggs and early larvae of the sicydiine goby Stiphodon percnopterygionus were investigated on Okinawa Island, southern Japan. Spawning season was estimated as being from May to December. Standard length at maturity was approximately 20 mm in both sexes, and batch fecundity was approximately 1000–10 000 per female. The egg masses, guarded by the male, were laid on the undersurface of stones in freshwater. The pyriform eggs had long- and short-axis diameters of 0.54–0.58 mm and 0.49–0.50 mm, respectively. Newly hatched larvae (1.20–1.32 mm notochord length: NL) were poorly developed, with large yolk sacs and unopened mouths. Three days after hatching (1.87–2.05 mm NL), eyes were fully pigmented and mouths were opened. An erratum to this article is available at .