Western corn rootworm (Diabrotica virgifera virgifera LeConte) (Coleoptera: Chrysomelidae) oviposition can be released by decapitation

Nervous system control of western corn rootworm (Diabrotica virgifera virgifera LeConte, WCR) (Coleoptera: Chrysomelidae) oviposition was studied using decapitation. Gravid females (n = 364) were decapitated with scissors and floated in water-filled Petri dishes. Oviposition by individuals was observed at 30 min intervals for 4 hr after decapitation; cumulative oviposition was tallied at 48 hr post-treatment. Overall, 82.7% of females laid eggs within 48 hr. Oviposition commenced quickly; 78.4% of females laid eggs during the observation period, 81.8% of these began egg laying within 30 min of decapitation. Egg-laying females deposited a total of 66.8 ± 2.1 eggs (mean ± SEM); this was 85.1% of the total mature egg load. Dissection revealed that 31.9% of n = 301 laying females and 14.3% of 63 non-laying females had a rupture of the common oviduct, manifest as an egg-filled hernia containing a mean of 8.17 ± 1.3 eggs (range: 1–83). Among n = 237 females that laid eggs during observations, females with hernias laid significantly fewer eggs (35.8 ± 4.2) than intact females (48.0 ± 2.7) during the 4-hr interval. There was no difference in the mean proportion of hatch for eggs collected from the same n = 10 females before (0.88 ± 0.03) or after decapitation (0.84 ± 0.04). Rapid oviposition following decapitation suggests that WCR egg laying is under constant descending neural inhibition; the motor programme controlling egg laying must reside posterior to the head. Decapitation can be used to quickly collect mature, fertilized WCR eggs.     

Predation of Clitostethus arcuatus (Col.: Coccinellidae) on Trialeurodes vaporariorum (Hem.: Aleyrodidae)

Greenhouse whitefly, Trialeurodes vaporariorum, is a serious pest of glasshouse crops. It shows resistance to different insecticides and growers are interested in finding other useful control methods. This research was carried out to study the predation potential and biology of Clitostethus arcuatus (Rossi) as one of the most important predators of this pest. Adult C. arcuatus were reared on tobacco leaves bearing colonies of greenhouse whitefly eggs under controlled conditions (25±2°C, 65±5% RH and 16 h L:8 h D). Results showed that the average developmental time of the egg, first through fourth instar larva and pupa were 2.82±0.12, 4.47±0.14, 4.54±0.1, 6.3±0.2, 7±0.22 and 3.8±0.13 days, respectively; and longevity of female and male were 66.4±2.6 and 54.9±2.5 days, respectively. The average feeding rates of female, male and larvae (first through fourth) were 61.4±0.7, 27.6±0.9 eggs/day and 12±1.03, 30.3±2.4, 41.3±2, 68.04±2 eggs/day, respectively. The larvae consumed an average of 992.2±36 eggs during the total larval developmental period with a daily mean of 45.8±0.5. A significant difference was shown between the feeding rate of fourth instar larval stages and between sexes. Females, males and one pair of C. arcuatus (♀,♂) consumed an average of 17.2±0.4, 10.6±0.8, 23.1±0.5 nymph/day; 28.5±0.9, 20.3±0.6, 47.2±0.6 pupa/day and 8±0.3, 6.5±0.54, 13.6±0.4 adult/day, respectively. The feeding rate was significantly different among whitefly life stages. Females laid an average of 3±0.23 eggs/day.     

Biology and host specificity of <Emphasis Type="Italic">Gonatocerus deleoni</Emphasis> (Hymenoptera: Mymaridae), a potential biocontrol agent of <Emphasis Type="Italic">Homalodisca vitripennis</Emphasis> (Hemiptera: Cicadellidae) in California,USA

The host-specificity and biological traits of Gonatocerus deleoni Triapitsyn, Logarzo & Virla (Hymenoptera: Mymaridae), a potential candidate for biological control of the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), were determined under laboratory conditions. G. deleoni is a solitary egg parasitoid native to Argentina, originally reared from sentinel eggs of Tapajosa rubromarginata (Signoret) (Cicadellidae). With GWSS as a fictitious host, G. deleoni’s average development time from oviposition to adult emergence was 18.8 ± 1.4 days, with males developing faster than females (18.0 ± 1.3 days, males; 19.0 ± 1.3 days, females). The average parasitism rate on 1–8-day-old eggs was 45.7% but this was significantly affected by the age of the egg, ranging from 1.4% to 69.9% (egg ages 8 and 3, respectively). The average sex ratio was 0.34 (percent males) and sex ratio was not significantly affected by egg age. G. deleoni was able to develop in eggs of GWSS and Homalodisca liturata Ball (both in the tribe Proconiini), but was unable to develop on eggs of Graphocephala atropunctata (Signoret) (different tribe, same subfamily) or Erythroneura elegantula Osborn (different subfamily).     

Effect of temperature on development and reproduction of Neoseiulus barkeri (Acari: Phytoseiidae) fed on Aleuroglyphus ovatus

The effect of five constant temperatures (16, 20, 24, 28 and 32°C) on the development, survival and reproduction of Neoseiulus barkeri Hughes fed on Aleuroglyphus ovatus Toupeau (Acari: Acaridae) was examined in the laboratory at 85% relative humidity. Development time of different immature stages decreased with increasing temperature, total egg-to-adult development time varied from 5.0 ± 0.13 to 17.5 ± 0.29 days. The lower thermal threshold for development was 9.7 ± 2.48°C and the thermal constant from egg to adult was 111.1 ± 12.34 degree-days. Pre- and post-oviposition period and female longevity all shortened as temperature increased. The longest oviposition period was observed at 24°C with 20.4 ± 1.13 days. At 20, 24, 28 and 32°C, mated females laid on average 0.7 ± 0.08, 1.5 ± 0.04, 1.6 ± 0.11 and 1.5 ± 0.11 eggs per day, respectively, but no eggs were laid at 16°C. Both the maximum fecundity (30.9 eggs per female) and the highest intrinsic rate of increase (r _m = 0.166) were obtained at 28°C. The results of this study indicated that a mass rearing of N. barkeri with A. ovatus as prey is feasible at the appropriate temperature.     

The life cycle of Hyalomma rufipes (Acari: Ixodidae) under laboratory conditions

Biological characteristics of Hyalomma rufipes parasitising on rabbits and sheep were compared under laboratory conditions in Gansu, China. Mature ticks could parasitize both rabbits and sheep, while immature ticks only fed on rabbits successfully. Adults sucked blood on sheep significantly longer than on rabbits (16 and 13 days, respectively). Other adult parasite characteristics fed on the two hosts were similar, including the weight of engorged adult, female daily oviposition, and the weight and amount of the egg mass laid. Those indicated that this tick species showed little host specificity between sheep and rabbits during its adult stage. In total, the life cycle of H. rufipes was completed in an average period of 179 days. The average developmental periods were 59 days for egg incubation, 3 and 21 days for immature tick prefeeding and feeding, 2, 12 and 40 days for adult prefeeding, female preoviposition and oviposition. The longer female fed for engorgement, the shorter preoviposition period of engorged female needed, although when the feeding period was less than 15 days, this relationship was not obvious. The results confirmed the correlation between the weight of the engorged female and the number of eggs laid (r = 0.909). The reproductive efficiency index (REI) and reproductive fitness index (RFI) in females was 10.63 and 7.22, respectively. Engorged nymphs moulting to females were significantly heavier (27.6 ± 0.89 mg) than those moulting to males (22.3 ± 0.52 mg). Males outnumbered females by 1.4:1.     

<Emphasis Type="Italic">Fopius arisanus</Emphasis> oviposition in four <Emphasis Type="Italic">Anastrepha</Emphasis> fruit fly species of economic importance in Mexico

We studied the oviposition performance of Fopius arisanus (Sonan) (Hymenoptera: Braconidae) attacking eggs of four fruit flies of the genus Anastrepha Schiner (Diptera: Tephritidae) under laboratory conditions. The complete process of oviposition on an individual egg of Anastrepha ludens (Loew) lasts in average 85.4 ± 2.9 s, including a tremor (25.8 ± 1.03 s) observed in the middle of this process related to the egg’s descent. The average parasitism of A. ludens egg was 60.9 ± 7.5%, with only 1.2% of superparasitized eggs. During individual acts of oviposition, we noted that F. arisanus possesses a highly flexible ovipositor that curves easily as it searches for additional suitable eggs, which may be of particular benefit when a female finds large clutches of eggs. The individual oviposition of F. arisanus in host fruits attacked by Anastrepha spp. varies with the egg clutch size of each fruit fly species: A. serpentina laid the biggest egg clutches (21.3 ± 1.4), followed by A. ludens (14.2 ± 0.9), and A. striata (1.0 ± 0.0) (=A. obliqua). The time spent by F. arisanus in individual ovipositions was parallel to these findings, reinforcing the idea that F. arisanus attacks several eggs in each individual insertion of its ovipositor. Neither formal oviposition acts, nor adult emergences of F. arisanus were registered in A. obliqua. We discuss the potential of F. arisanus as natural enemy of fruit flies of the genus Anastrepha, and explore the eventual developing of its mass rearing. Handling Editor: Torsten Meiners.     

Potential of parasitoid Gronotoma micromorpha Perkin (Hymenoptera: Eucoilidae) as a biocontrol agent for pea leafminer fly,Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae)

The potential of the parasitoid, Gronotoma micromorpha (Perkin) as a biological control agent for pea leafminer fly, Liriomyza huidobrensis (Blanchard) has been evaluated in a series of studies on the fly preference to host instars, biological characteristic and functional response to the host density. The studies were carried out at the Laboratory of Integrated Pest Management (IPMLab), Faculty of Agriculture Udayana University in Denpasar and Greenhouse Owned-Farmer in Pancasari Buleleng, Bali (1200 m asl; average temperature 23.67 ± 5.69 °C and average RH of 64 ± 17.69%). The results showed that G. micromorpha has a strong preference towards the 3rd instar larvae of L. huidobrensis. The pre-oviposition period was 0.4 ± 0.67^d, oviposition was 12.5 ± 2.0^d and post-oviposition period was 1 ± 0.0^d while the peak oviposition occurred on the 4th day. Meanwhile, all the offsprings produced were females which indicated that parthenogenesis thelytokous was present in G. Micromorpha and the fecundity was 29 ± 3.77 per female adult. Furthermore, the average life span for the adult was 13 ± 1.42 days with an oviposition period of 12.5 ± 2.01 days. The average post-oviposition period was 1 ± 0.0 days and average development period of egg to adult was 32.03 ± 0.98 days. Meanwhile, the breeding potential was high with an average daily percentage of 2.27 ± 0.27 fecundity and a maximum spawning occurred on day 4. The functional response was type-2 and it is the rate at which parasitism increase with increase in population of the host density. Hence, the biological characteristics and mode of functional response by the parasitoid showed its potential as a biological pesticide for pea leafminer L. huidobrensis.     

绿翅鸭繁殖生态初报

2007～2009年在黑龙江中南部地区对绿翅鸭(Anas crecca)繁殖生态习性进行了观察。绿翅鸭在黑龙江属夏候鸟,每年3月末4月初迁来,10月上旬迁离,所观察的4对绿翅鸭居留期约6个月。迁来时成群停留在湖泊及江的冰面上,开江以后散去,繁殖期间,绿翅鸭的配偶关系为一雄一雌,巢址多选择离水域较近的草丛或灌木丛中,所观察的4巢,巢都比较简单,筑巢时间为(5.5±1.0)d(n=4)。巢筑成后的(3.25±0.50)d开始产卵。每窝70～12枚不等,平均(9.80±2.21)枚(n=4)。卵重平均(28.70±0.72)g(n=39),最后一枚卵产出后(2.50±0.577)d(n=4),开始孵卵,孵卵期约为22～26 d不等,平均孵卵期为(24.25±1.17)d(n=4),平均孵化率为79.5%±29.98%。幼鸟为早成鸟,育雏期为(29.75±1.70)d。     

Reproductive success of wild Lesser Rheas (Pterocnemia -Rhea- pennata pennata) in north-western Patagonia, Argentina

We studied the reproductive success of a wild Lesser Rhea population (Pterocnemia -Rhea- pennata pennata) during two reproductive seasons (2004/2005 and 2005/2006) in north-western Patagonia, Argentina. The parameters recorded included population and nest density, clutch size, hatching success, chick survival (up to 3 months of age) and percentage of chicks that reached the juvenile stage after the winter. We also estimated the percentage of males that attempted to nest and of those that were successful (those producing at least one chick), daily nest mortality rates (DNMR) at different stages of the nesting cycle and the probability that an egg that has been recently laid will produce a chick. On average, both years pooled, the density of this population of Lesser Rheas was 1.55 ± 0.2 individuals/km² (SE), nest density was 0.17 ± 0.04 per km ² , clutch size was 20.8 ± 6.4 eggs, hatching success was 74.4% ± 11.3, Mayfield’s probability of an egg that will produce a chick was 0.64, chick survival was 65.4% ± 14.5 and percentage of chicks that reached the juvenile stage was 26.3%. Nearly a quarter of Lesser Rhea males in the population attempted to nest during a breeding season, and the DNMR was significantly higher during the laying stage (most nest failures were due to anthropogenic disturbances related to livestock raising activities). Nesting success, hatching success, and chick survival of Lesser Rheas were higher than those of their most closely related species, the Greater Rhea (Rhea americana), whereas the percentage of chicks that reached the juvenile stage was similar due to high winter mortalities of chicks. We suggest that the increase in reproductive effort is a strategy of this species to overcome environmental constraints.     

Life table parameters of an indigenous strain of Neoseiulus californicus McGregor (Acari: Phytoseiidae) when fed Tetranychus urticae Koch (Acari: Tetranychidae)

The life table of the indigenous Neoseiulus californicus was studied at different temperatures and 65 ± 5% relative humidity under conditions of 16 h light : 8 h dark (LD 16:8). The total developmental period from egg to adult varied from 3.0 to 14.0 days at 15 to 35°C. Survival to adulthood ranges from 86.21 to 93.94%, with the highest rate at 25°C. The lower threshold temperature from egg to adult stages of females and males was 10.84 and 10.72°C, respectively, and the thermal constant was 57.14 degree‐days (DD) for females and 56.18 DD for males. Total number of eggs laid by each female was the highest (70.38 eggs) at 25°C, whereas average daily fecundity was the highest (3.69 eggs/female/day) at 30°C. The net reproductive rate was the highest (48.49) at 25°C and lowest (26.18) at 30°C. Mean generation time decreased from 19.04 to 11.47 days with increasing temperature from 20 to 30°C. Both intrinsic rate of natural increase (0.284) and finite rate of increase (1.32) were maximum at 30°C. Adult longevity was the highest (42.75 days for females and 32.60 days for males) at 20°C and lowest (22.70 days for females and 15.30 days for males) at 30°C. Sex ratio was female biased and was the highest (78.08) at 25°C and lowest (70.24) at 30°C. Developmental data of five constant temperatures, temperature thresholds and thermal requirements may be used to predict the occurrence, number of generations and population dynamics of N. californicus as an important biocontrol agent of Tetranychus urticae.     

Erythritol ingestion impairs adult reproduction and causes larval mortality in Drosophila melanogaster fruit flies (Diptera: Drosophilidae)

Previous feeding studies showed the polyalcohol erythritol was toxic when ingested by adult laboratory fruit flies (Drosophila melanogaster). We asked whether erythritol could additionally affect fly population growth either through larval toxicity or through effects on adult reproduction. Females did not avoid laying on food substrates with 1M erythritol; laying rate on 1M erythritol food was similar to control food when females were given free‐choice access. Eggs laid or placed on 0.5 M to 2.5 M erythritol foods hatched at normal rates, suggesting erythritol was not toxic to eggs upon contact. Drosophila melanogaster larvae readily consumed food containing 1 M erythritol, but none of these larvae reached pupation. Longevity of larvae feeding on in 1 M erythritol food was significantly reduced relative to controls, and mean ± SE larval lifespan on erythritol was 1.54 ± 0.10 days (max. = 3 days). Exposing cohorts of second‐instar larvae to food with varying concentrations of erythritol showed the LD50 (at 24 hr) concentration was approximately 0.6 M. Taken together, these results suggest erythritol could be employed in effective larval‐sink baits. Adults flies fed with erythritol produced significantly fewer eggs on days when they fed on 1 M erythritol, and egg production was significantly reduced for one additional day after the adults were moved to control food. These findings suggest erythritol is rapid and effective at temporarily suppressing D. melanogaster reproduction, increasing its potential for use in effective insect population control.     

Spawn and development of the olivid gastropod Olivancillaria carcellesi from north Patagonia,Argentina

Olivancillaria carcellesi occurs in shallow sandy shores from north Patagonia, in intertidal and subtidal sandy bottoms. Females of O. carcellesi exhibited a remarkable specificity for spawning on the shells of living males and females, indiscriminately, of the buccinanopsid Buccinastrum deforme, measuring 26.9 ± 4.7 mm in shell length. The egg capsule was semispherical and attached to B. deforme shells by a small elliptical and wide base. The capsule was translucid when spawned, with a thick and semirigid wall and a hatching aperture of 1.8 ± 0.1 mm (n = 111) in diameter. Each egg capsule contained a single egg that measured 1367 ± 34 μm (n = 5) in diameter before cleavage. The embryo developed a small bilobed velum and an operculum, which were both lost before hatching as a crawling juvenile of 1762 ± 47 μm (n = 28) in shell length. As in other species in the genus, the eggs of O. carcellesi are among the largest in the caenogastropods with direct development. The time from oviposition to hatching is estimated to be approximately 6 months.     

Reproductive traits of shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque, 1820) in the lower Platte River,Nebraska

We assessed reproductive status, fecundity, egg size, and spawning dynamics of shovelnose sturgeon Scaphirhynchus platorynchus in the lower Platte River. Shovelnose sturgeon were captured throughout each year during 2011 and 2012 using a multi‐gear approach designed to collect a variety of fish of varying sizes and ages. Fish were collected monthly for a laboratory assessment of reproductive condition. Female shovelnose sturgeon reached fork length at 50% maturity (FL₅₀) at 547 mm and at a minimum length of 449 mm. The average female spawning cycle was 3–5 years. Mean egg count for adult females was 16 098 ± 1103 (SE), and mean egg size was 2.401 ± 0.051 (SE) mm. Total fecundity was positively correlated with length (r² = 0.728; P < 0.001), mass (r² = 0.896; P < 0.001), and age (r² = 0.396; P = 0.029). However, fish size and age did not correlate to egg size (P > 0.05). Male shovelnose sturgeon reached FL₅₀ at 579 mm and at a minimum length of 453 mm. The average male spawning cycle was 1–2 years. Reproductively viable male and female sturgeon occurred during the spring (March–May) and autumn (September–October) in both years, indicating spring and potential autumn spawning events. Shovelnose sturgeon in the lower Platte River are maturing at a shorter length and younger age compared to populations elsewhere. Although it is unknown if the change is plastic or evolutionary, unfavorable environmental conditions or over‐harvest may lead to hastened declines compared to other systems.     

Reproduction of the wedge sole (<Emphasis Type="Italic">Dicologoglossa cuneata</Emphasis> Moreau) in captivity: spawning parameters and influence of the natural temperature

In this work, the wedge sole (Dicologoglossa cuneata) spawning under a natural thermocycle has been studied. The spawning parameters were similar to those of other flatfish in captivity, the relative fecundity being very high (1.7 ± 0.1 × 10⁶ eggs kg female⁻¹ per spawning season). The percentage of floating eggs decreased with time and was directly related to egg diameter, daily relative fecundity and fertilization rate. Nevertheless, the hatching rate variations were not correlated to any other spawning parameter. The temperature range during the spawning season was very wide (11–21°C) though the largest spawns occurred between 12 and 16°C. The natural temperature cycle influenced wedge sole egg production, the winter temperature minimum indicating the onset of spawning, but the variations in the reproductive season did not appear to affect the daily egg production. Future research should focus on the photoperiod and its interaction with temperature as key factor for spawning.     

Maximum realised lifetime parasitism and occurrence of time limitation in Gonatocerus ashmeadi (Hymenoptera: Mymaridae) foraging in citrus orchards

The relationship between body size (hind tibia length), <12 h egg load, wing wear and parasitoid age was used to estimate realised lifetime parasitism of recently dead Gonatocerus ashmeadi collected in a citrus orchard. Under prevailing field conditions and methodology assumptions, it was estimated that female G. ashmeadi lived on average for 183 ± 17 degree-days, parasitised a total of 87 ± 9 Homalodisca vitripennis eggs, and died with 34 ± 5 eggs remaining in the ovaries. Only 17% of dead G. ashmeadi died with no mature eggs suggesting that 83% of G. ashmeadi were not egg limited at time of death. Estimates of realised lifetime parasitism for female G. ashmeadi under prevailing field conditions in July and August in a southern California citrus orchard indicated that time of year had a significant effect on reproductive output. Additionally, live G. ashmeadi captured daily during June through August 2006 had body size, egg load and wing wear recorded to detect possible monthly changes in parasitoid age and egg load. Foraging G. ashmeadi captured alive in June were older and oviposited more eggs in the field compared with August. Only 0.5% of live G. ashmeadi were captured with no mature eggs in their ovaries indicating that the vast majority of live G. ashmeadi were not egg limited.     

Age‐ and temperature‐dependent oviposition model of Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) with Tetranychus urticae as prey

In this study, we developed an oviposition model of Neoseiulus californicus (McGregor) with Tetranychus urticae Koch as prey. To obtain data for the model, we investigated the longevity, fecundity and survivorship of adult female N. californicus at six constant temperatures (16, 20, 24, 28, 32 and 36°C), 60–70% RH and a photoperiod of 16 : 8 (L : D) h. Longevity (average ± SE) decreased as temperature increased and was longest at 16°C (46.7 ± 5.25 days) and shortest at 36°C (12.8 ± 0.75 days). Adult developmental rate (1/average longevity) was described by the Lactin 1 model (r² = 0.95). The oviposition period (average±SE) was also longest at 16°C (29.8 ± 2.93 days) and shortest at 36°C (6.7 ± 0.54 days). Fecundity (average±SE) was greatest at 24°C (43.8 ± 3.23 eggs) and lowest at 36°C (15.9 ± 1.50 eggs). The oviposition model comprised temperature‐dependent fecundity, age‐specific cumulative oviposition rate and age‐specific survival rate functions. The temperature‐dependent fecundity was best described by an exponential equation (r² = 0.81). The age‐specific cumulative oviposition rate was best described by the three‐parameter Weibull function (r² = 0.96). The age‐specific survival rate was best described by a reverse sigmoid function (r² = 0.85).     

Biology of Bactrocera (Zeugodacus) tau (Walker) (Diptera: Tephritidae)

The biology of the fruit fly Bactrocera tau, an important horticultural pest, was studied under laboratory conditions at 25°C and 60–70% relative humidity on Cucurbita maxima. The duration of mating averaged 408.03 ± 235.93 min. After mating, the female fly had a preoviposition period of 11.7 ± 4.49 days. The oviposition rate was 9.9 ± 8.50 eggs and fecundity was 464.6 ± 67.98 eggs/female. Eggs were elliptical, smooth and shiny white, turning darker as hatching approached, and measured 1.30 ± 0.07 mm × 0.24 ± 0.04 mm. The chorion has polygonal microsculpturing and is species-specific with polygonal walls. The egg period lasts for 1.3 ± 0.41 days. The duration of the larval period is 1.2 ± 0.42, 1.7 ± 0.48 and 4.0 ± 0.94 days for first, second and third instars, respectively. Pupation occurs in the sand or soil and pupal periods are 7.0 ± 0.47 days. The life cycle from egg to adult was completed in 14.2 ± 1.69 days; the longevity of mated females and males was 130.33 ± 14.18 and 104.66 ± 31.21 days, respectively. At least two to three generations were observed from June 2008 to June 2009.     

Biology, life table and predation of Feltiella acarisuga (Diptera: Cecidomyiidae) feeding on Tetranychus cinnabarinus eggs (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common predatory gall midge, which feeds on many species of spider mites. All major life history and life table parameters of F. acarisuga were determined using the carmine spider mite, Tetranychus cinnabarinus (Boisduval) eggs as prey under laboratory conditions [26.7 ± 2 °C, 75 ± 5% RH, and a photoperiod of l4:10 (L:D) h]. Developmental times of F. acarisuga were 2.6, 7.1, and 6.7 d for eggs, larvae, and pupae, respectively, with an average of 16.4 d from egg to adult emergence. Female immatures development took ≈1 d longer than male immatures did. Adult F. acarisuga lived an average of 12.8 d, and the female adults (13.3 d) lived significantly longer than male adults did (11.9 d). After an average of 1.5 d preoviposition period, each female laid an average of 27.3 eggs in its life span with an average of 2.1 eggs per day and an average of 2.8 eggs on each of its oviposition day. The raw data were analyzed using an age-stage, two-sex life table method that takes into consideration of the variable developmental rates among individuals and between sexes. The intrinsic rate of natural population increase (r), net reproductive rates (R_o), gross reproductive rate (∑m_x), generation time (T), and doubling time (DT), and the finite rate of increase (λ) of F. acarisuga were estimated using the age-stage, two-sex (male and female) life table analysis as 0.122 d⁻¹, 16.19 eggs per female, 20.81 eggs per female, 22.81 d, 1.1298 d, and 5.7 d⁻¹, respectively. Each of the first, second, and third instar larvae of F. acarisuga consumed an average of 35.5, 54.0 and 86.9 T. cinnabarinus eggs per day, respectively. Larvae of F. acarisuga could consume an average of 175.4, T. cinnabarinus eggs, and female larvae consumed 14% more spider mite eggs (187.6 eggs) than male larvae (165.1 eggs). The significance of other life table parameters related to the population and the potential of using F. acarisuga as a biological control agent are discussed.     

Life cycle and behaviour of the predaceous mite <Emphasis Type="Italic">Cunaxatricha tarsospinosa</Emphasis> (Acari: Prostigmata: Cunaxidae)

Life cycle and behaviour of Cunaxatricha tarsospinosa Castro & Den Heyer from rubber trees in Brazil were studied, with Tenuipalpus heveae Baker offered as prey. The study was conducted at 25.4 ± 0.2°C, 83 ± 5% RH and 12:12 h L:D photophase. The egg stage was the longest immature stage, lasting 17.1 ± 1.3 days (mean ± SE); total juvenile development was completed in 33.2 ± 2.8 days. Lifetime fecundity was 12.0 ± 2.2 eggs. Intrinsic rate of population increase was low, suggesting that T. heveae may not be a good prey for the predator. All specimens of C. tarsospinosa collected in the field for this study were females, no males were found. Concurrently, only females were obtained in the laboratory. This seems to be the first report of thelytokous parthenogenesis for cunaxids. Similar to earlier reports for some Cunaxinae and Coleoscirinae, prey were captured when predators were actively searching for them.     

Modulating effect of a magnetic field on Saprolegnia parasitica,Coker, 1923 infecting trout (Salmo trutta,L.) eggs

The aim of study was to investigate the effects of static magnetic fields [1 mT (miliTesla), 5 and 10 mT] on Saprolegnia parasitica growth, development, and cytotoxicity in the infection of trout eggs in hatcheries under laboratory and industrial conditions. The egg envelope (SEM) structures resulting from infection with and development of S. parasitica are also presented. S. parasitica mycelium was cultured on a microbiological medium SDA in Petri dishes (4 ± 0.2°C, 97% humidity) exposed to a magnetic field and in a control, to assess the mycelium growth rate. Effects of the magnetic field on cytotoxicity of S. parasitica after a 21‐day incubation on SDA medium were analyzed using the colorimetric cytotoxicity test MTT. Eggs of brown trout Salmo trutta were infected with S. parasitica by inoculum and incubated in glass vessels (4 ± 0.2°C) in a magnetic field and a control. The degree of mycelium invasion of the egg envelopes and the percentage of egg mortality were recorded daily thoughout the period of embrionic development. The magnetic field effects on brown trout eggs infected by wild strains of fungus‐like organisms (FLO) in the hatchery (4°C ± 0.1) were also investigated. Changes in the structure of brown trout egg envelopes as a result of infection and development of S. parasitica were examined in a FIB/SEM. The effects of magnetic fields of 5 and 10 mT on slowing the growth of mycelium of S. parasitica in vitro were also observed. Determining biochemical properties of S. parasitica also showed the effects of the magnetic field in differentiating the cytotoxicity. All magnetic field values showed a distinct decrease from medium to low values of S. parasitica cytotoxicity; the most effective reduction was observed at 5 mT. Magnetic fields in all tested levels slowed development of the mycelium on the incubated trout eggs, resulting in a decrease in the number of eggs infected by S. parasitica and thus permitting a greater hatching success. Similar effects were observed in other hatching conditions where eggs were also exposed. No negative effects of magnetic field treatment on the condition of the newly‐hatched larvae were observed. The SEM and FIB (Focused Ion Beam) analyses revealed penetration of S. parasitica via radial canals of the envelope. The magnetic field had no effect on the structure of hyphae or sporangia of S. parasitica, but did affect the growth rate of mycelium on the egg surface.