Determination of Homalodisca coagulata (Hemiptera: Cicadellidae) egg ages suitable for oviposition by Gonatocerus ashmeadi, Gonatocerus triguttatus, and Gonatocerus fasciatus (Hymenoptera: Mymaridae)

Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) eggs 1–10 days of age were exposed to Gonatocerus ashmeadi Girault, Gonatocerus triguttatus Girault, and Gonatocerus fasciatus Girault (all Hymenoptera: Mymaridae) in no choice laboratory trials to investigate egg age utilization and to determine which egg ages are vulnerable to attack by these three parasitoids. The H. coagulata egg ages that were most suitable for oviposition by G. ashmeadi, G. triguttatus, and G. fasciatus were eggs 3, 4, and 2 days of age, respectively. Egg ages least suitable for parasitoid development were 6–10 days for G. ashmeadi (resulting in <50% parasitism), 1–2 and 7–10 days for G. triguttatus (resulting in <25% parasitism), and 3–10 days for G. fasciatus (resulting in <11% parasitism). Pooling parasitism data across all egg ages showed that parasitism by G. ashmeadi was 12.9 and 28.5% higher compared with G. triguttatus and G. fasciatus, respectively, and G. triguttatus resulted in 15.6% higher percentage parasitism compared with G. fasciatus. Egg age had a significant effect on the percentage of female G. ashmeadi offspring produced, but this was not significant for G. triguttatus, and low G. fasciatus parasitism prevented statistical analyses for comparisons. Results from tests where females were offered a choice for oviposition between eggs 1, 3, and 5 days of age demonstrated that G. ashmeadi and G. triguttatus showed no significant oviposition preference, while percentage parasitism by G. fasciatus was 29.4 and 7.4% higher when females were presented eggs 1 and 3 days of age, respectively, compared with eggs 5 days of age. Choice tests indicated that an overlap in egg age suitability for oviposition exists between G. ashmeadi, G. triguttatus, and G. fasciatus, and that interspecific competition for eggs 1, 2, and 3 days of age may occur in the field environment.     

Effect of Temperature on the Life History of Cirrospilus sp. near lyncus (Hymenoptera: Eulophidae), a Parasitoid of Phyllocnistis citrella (Lepidoptera: Gracillariidae)

The effect of four constant temperatures on the life history of Cirrospilus sp. near lyncus was examined in the laboratory. This species is one of the most abundant generalist indigenous parasitoids of the citrus leafminer, Phyllocnistis citrella Stainton, in Spain. Adult lifespan of C. sp. near lyncus decreased from 50.2 to 9.1 days as temperatures increased from 15 to 30°C, respectively. Both gross fecundity and host-feeding were highest at 20°C (170.48 eggs and 32.33 hosts). Oviposition rates were optimal at higher temperatures (5.22 eggs per day at 25°C and 4.79 eggs per day at 30°C) and were dependent on female age. In contrast, host-feeding rates for a given temperature did not depend on age. Generation time decreased with increasing temperatures from 68.05 days at 15°C to 12.19 days at 30°C. Net reproduction peaked at 20°C (68.86 viable females per female). Intrinsic rate of increase doubled from 15°C (0.059 females per female per day) to 20°C (0.127 females per female per day) and almost doubled again from 20 to 30°C (0.210 females per female per day). Given these parameters, C. sp. near lyncus could perform optimally in the area occupied by P. citrella in the Mediterranean region.     

Life table and predation of Oligota pygmaea (Coleoptera: Staphylinidae) a major predator of the red spider mite, Oligonychus coffeae (Acarina: Tetranychidae) infesting tea

The staphylinid beetle, Oligota pygmaea (Solier) is an important predator of the red spider mite, Oligonychus coffeae (Nietner) infesting tea. Biology, life table and predatory efficiency of O. pygmaea were studied under laboratory conditions. Duration of developmental stages of O. pygmaea was 3.2, 5.7 and 12.5 d for eggs, larvae and pupae, respectively with an average of 23.0 d from egg to adult emergence. After a mean preovipostion period of 2.9 d, each female laid an average of 400.5 eggs in its life span. Adult O. pygmaea lived for an average of 54.1 d. Adult females lived for a longer period of 58.8 d compared to the longevity of 49.4 d of adult male. Studies revealed that its life table characterized by an intrinsic rate of natural population increase (r) of 0.118 d, net reproductive rates (R_o) of 243.693 eggs/female, gross reproduction rate (Σm_x) of 245.313 eggs/female, generation time (T) of 46.575 d, doubling time (DT) of 5.874 d and finite rate of increase (λ) of 1.125 d. Seasonal abundance of O. pygmaea and its prey, O. coffeae was monitored by sampling 25 tea leaves randomly from each experimental block grown under the prevailing field conditions. O. pygmaea showed a typical pattern of population dynamics with a peak during January to March and low incidence during June to September. Peak in the population of O. pygmaea coincided with the abundance of O. coffeae in the tea fields. Weather factors such as high temperature, low relative humidity and low sunshine hours adversely affected the populations of O. pygmaea. The first to third instar larvae of O. pygmaea consumed 31.0–133.2 eggs of mites per day. Third instar larva of O. pygmaea consumed an average of 133.2 eggs, 46.4 hexapod larvae, 39.6 nymphs and 11.4 adults per day. Adult females consumed more number of red spider mites compared to the males.     

Development of Encarsia bimaculata (Heraty and Polaszek) (Hymenoptera: Aphelinidae) in Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) nymphs

Encarsia bimaculata was recently described from India as a potentially useful parasitoid of Bemisia tabaci. Its developmental biology was studied in the laboratory at 25–30 °C and 70–75% RH. Results showed that E. bimaculata is a solitary, arrhenotokous, heteronomous, autoparasitoid. Mated females laid eggs internally in B. tabaci nymphs that developed as primary parasitoids. Males developed as hyperparasitoids, either in females of their own species or in other primary aphelinid parasitoids. Superparasitism was common under cage conditions. Both sexes have an egg, three larval instars, prepupal, and pupal stages. Development from egg to adult took 12.70 ± 2.10 days for females and 14.48 ± 2.60 days for males. Individual B. tabaci nymphs were examined for E. bimaculata parasitization using three isozymes: esterase, malate dehydrogenase, and xanthine dehydrogenase. All three isozymes showed differential banding patterns that identified E. bimaculata parasitized or unparasitized B. tabaci nymphs.     

Life history of the tick parasitoid Ixodiphagus hookeri (Hymenoptera: Encyrtidae) in Kenya

We conducted laboratory and field experiments to elucidate the life history of Ixodiphagus hookeri, a parasitoid of the ixodid tick Amblyomma variegatum in Western Kenya. Ixodiphagus hookeri females oviposited in unfed host nymphs as well as engorged nymphs, but rarely in engorged larvae. While I. hookeri developed to adults in engorged nymphs, the eggs laid in unfed nymphs disappeared within 2 days after oviposition. As temperature increased, development time of I. hookeri from oviposition to adult emergence in engorged nymphs decreased from 46 days at 23 °C to 35 days at 28 °C, and their immature survival in engorged nymphs decreased from 67% at 23 °C to 22% at 28 °C. No parasitoid adult emerged from hosts at 30 °C. Individual hosts parasitized by single females produced 42–53 adult wasps, 73% of which were females. As a typical pro-ovigenic species, I. hookeri females had an average of 84 mature eggs at emergence and lived only for a few days. When laboratory-reared, unfed nymphs of A. variegatum were attached to cattle for 4–9 days in subsistence farmers’ fields in Western Kenya, 25% of the engorged nymphs and 4% of the unfed nymphs on cattle were parasitized by I. hookeri, demonstrating that I. hookeri females search for and oviposit in A. variegatum nymphs on cattle. Unlike other strains of I. hookeri that overwinter as eggs in unfed nymphs, I. hookeri could continuously reproduce throughout the year in Western Kenya.     

Population structure and reproductive biology of Atlantoscia floridana (van Name, 1940) (Crustacea, Isopoda, Oniscidea) in southern Brazil

Data were obtained on the population structure and reproduction of Atlantoscia floridana, one of the most common species of terrestrial isopods in the restinga (coastal dune) forests of the state of Rio Grande do Sul, southern Brazil. During a 19-month period, a total of 7833 individuals were sampled: 2792 males, 3400 females and 1691 mancas. There was a significant difference between the size of both males and females collected in 2000 and 2001: the mean size was smaller in the second year when individuals in the larger size classes were lacking. Population density varied with season. The minimum population was 131 ind per m² individuals, the maximum 1040 ind per m² and the mean 450  per m². While the overall sex ratio was clearly female biased, the operational sex ratio favored males, and showed no changes with season. Because both ovigerous and post-ovigerous females were present throughout the year, reproduction is considered continuous; however, reproduction peaked during autumn and spring. Ovigerous females were measured (CW = cephalothorax width) and the number of eggs was counted. Fecundity (F) varied from 5 to 23 eggs ( = 11.18 ± 4) per female, and was expressed by the regression F = –18.48 + 22.59 CW, with the female cephalothorax width varying from 1.04 to 1.68 mm. Marsupial mortality was only 0.9%. Egg production was 588 eggs per m² in spring and 660 eggs per m² in autumn. Recruitment occurred in all months, and eggs, embryos and marsupial mancas were also present year-round. A. floridana is the dominant species of terrestrial isopod in the study area. Its most remarkable characteristic is its high reproductive investment.     

Production of Anagrus epos Girault (Hymenoptera: Mymaridae) on Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) eggs

Anagrus epos Girault (Hymenoptera: Mymaridae) is a natural enemy candidate for a classical biological control program targeting the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology or ecology of A. epos when it utilizes GWSS eggs as a host. Here, we report the results of laboratory studies that describe the host age preference for oviposition, longevity of A. epos adults provided with different food sources, and developmental rates at six different constant temperature regimes. Anagrus epos is a gregarious parasitoid in GWSS eggs with up to 14 adults emerging from each GWSS egg. In choice and no-choice tests for oviposition, A. epos females successfully parasitized all developmental ages of GWSS eggs (1–8 days old). In choice tests, parasitism rates were significantly higher in 1-, 3-, 4-, and 5-day-old GWSS eggs than in 2-, 6-, 7-, and 8-day-old eggs. If provided with honey and water, honey only, water only, or no food or water, A. epos females lived on average 8.2, 4.7, 2.6, and 1.6 days, respectively. Anagrus epos required 294.1 degree-days above a lower temperature threshold of 12.4 °C to develop from egg to adult (eclosion). Our results provide baseline information useful in the development of an efficient parasitoid mass rearing program for A. epos release and evaluation in California.     

Photoperiod and temperature studies to determine whether diapause is found in successive generations of the African phytoseiid,Euseius fustis (Pritchard and Baker) (Acari: Phytoseiidae)

Photoperiod and temperature conditions known to induce diapause in tropical arthropods were tested on two generations (G₀ and G₁) of the phytoseiid, Euseius fustis. Failure to lay eggs or a pre-oviposition period longer than 15 days were the criteria used to determine whether females were in diapause. Females reared from egg to adult and held throughout adult life under cyclic temperatures of 29/20°C in combination with long photophases of 16L: 8D and 14L: 10D showed no indication of aestival diapause. Similarly, hibernal diapause was not induced in females reared under a constant temperature of 18°C and a photophase of 8L: 16D. Under the various test conditions, females initiated oviposition within an average of 4 days. Overall, pre-oviposition patterns for G₀ and G₁ females were similar under the same test conditions. Reproductive patterns based on the mean number of eggs per female per day varied only slightly between generations for the same treatments. No behavioural or morphological attributes associated with diapause were observed.     

Potential of Haplothrips brevitubus (Karny) (Thysanoptera: Phlaeothripidae) as a predator of mulberry thrips Pseudodendrothrips mori (Niwa) (Thysanoptera: Thripidae)

The predation potential of Haplothrips brevitubus (Karny) for thrips was evaluated in the laboratory. When second stage larvae of Pseudodendrothrips mori (Niwa) were presented to an adult H. brevitubus at densities of 10, 20, 30, and 40 larvae per cage at 25 °C over 24 h, the number of larvae consumed per day increased with an increasing density up to 30. Predation of H. brevitubus exhibited the type II functional response. The mean development time of the egg, larva, and pupa of H. brevitubus were 4.5, 9.6, and 4.8 days, respectively, at 25 °C. The survival rate from egg to adult emergence was 94.7%. One H. brevitubus larva consumed 41.6 P. mori larvae on average during the total larval period. Adult longevity was 35.2 days in females and 34.6 days in males. The pre-oviposition period was 2.7 days and the oviposition period was 31.5 days. The lifetime fecundity was 120.1 eggs and the mean daily oviposition rate was 3.6 eggs. Calculated mean generation time (T) was 29.5 days, intrinsic rate of natural increase (r_m) was 0.162, and net reproductive rate (R₀) was 56.5. The r_m value of H. brevitubus was higher than that of Thrips palmi Karny and almost equal to that of Frankliniella occidentalis (Pergande). These results indicate that H. brevitubus has good potential as a predator of P. mori and is likely to be useful for controlling thrips.     

Effect of relative humidity on development, survival and reproduction of the predatory lacewing Dichochrysa prasina (Neuroptera: Chrysopidae)

The effect of five constant relative humidity (RH) regimes (12%, 33%, 55%, 75% and 94%) on the preimaginal development and adult longevity and reproduction of Dichochrysa prasina Burmeister was studied at 26 ± 1 °C and a photoperiod of 16:8 (L:D) under laboratory conditions. For the experiments, larvae were fed individually on eggs of the flour moth Ephestia kuehniella (Zeller), whereas adults on a liquid diet consisting of water, yeast hydrolysate, sugar and honey. The experimental insects were maintained individually in sealed plastic containers with saturated water salt solutions at the base to control RH. Preimaginal developmental time from egg to adult for females and males was significantly shorter at 75% and 94% RHs than at other RHs in the range from 12% to 55%. Percentages of adult emergence were similar at all RHs tested and varied from 52.5% to 75.0%. Adult females that had no access to water and were maintained at 12%–75% RH lived on average less than two weeks and laid no eggs, whereas at 94% RH they lived longer and each laid on average 201 eggs. When the females had periodic access to a water source a significant increase in both longevity and egg production occurred and the estimated intrinsic rate of increase was high, irrespective of RH. These results could be useful for the mass-rearing of D. prasina and for better understanding its population dynamics under field conditions.     

Acceptance and suitability of different host stages of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and seven other tephritid fruit fly species to Tetrastichus giffardii Silvestri (Hymenoptera: Eulophidae)

Tetrastichus giffardii Silvestri is a gregarious eulophid endoparasitoid of several tephritid fruit fly species. Host stage suitability was studied using nine age groups of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), namely, eggs less than 24 h and between 24 and 48 h old, and 1- to 7-day-old larvae. Life table studies for T. giffardii using C. capitata as host were done at 26 ± 5 °C and 55–60% RH. Egg load in relation to age of the female parasitoid was also assessed as was the effect of host deprivation on adult longevity. Host acceptance and suitability were examined with respect to eight species of tephritids. Potential hosts so tested were five Ceratitis species, the Medfly, C. capitata, the mango fruit fly, Ceratitis cosyra (Walker), the Natal fruit fly, Ceratitis rosa Karsch, Ceratitis fasciventris (Bezzi), and Ceratitis anonae Graham; two Bactrocera species, the melon fruit fly, Bactrocera cucurbitae (Coquillett) and the newly invasive Bactrocera invadens Drew, Tsuruta, and White; and one Dacus species, the lesser pumpkin fly, Dacus ciliatus Loew. No parasitoids were obtained from eggs while all larval stages were suitable though at varying degrees. Parasitism and number of progeny was related to host age in a curvilinear manner with maxima at 4- to 5-day-old larvae. By contrast, development time decreased with age of host larvae while sex ratio was not affected. The intrinsic rate of increase was 0.17 ± 0.01; gross and net reproductive rates were 64.9 ± 4.3 and 44.9 ± 3.8, respectively. Non-ovipositing females lived significantly longer than ovipositing ones. The females accepted all host species tested, but only C. capitata, D. ciliatus and, to a much lesser extent, C. cosyra were suitable. In the remaining host species, most eggs were encapsulated. In C. capitata and D. ciliatus, percent parasitism was similar, but number of progeny was lower and the sex ratio, as the proportion of females, was higher when the parasitoid was reared on D. ciliatus. Progeny per puparium were also similar for the two hosts. In the light of these results it can be concluded that T. giffardii has a narrow host range, but it attacks and successfully develops in larvae representing a wide range of ages.     

Reproductive biology of Fopius ceratitivorus (Hymenoptera: Braconidae), an egg–larval parasitoid of the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

The reproductive biology of Fopius ceratitivorus Wharton, a recently discovered African parasitoid, was studied in quarantine in Hawaii to facilitate its mass production for biological control of the Mediterranean fruit fly, Ceratitis capitata. Mean longevity of host-deprived and ovipositing females was 17.3 ± 0.9 d and 16.2 ± 0.5 d, respectively. Ovarian maturation peaked at 61.6 mature eggs per female on the fifth day after eclosion and declined thereafter. Mean number of offspring produced per day by mated females was 5.1 ± 0.4, and realized fecundity expressed as total eggs deposited during the female’s life time was 107.8 ± 12.8. Females were more attracted, to and reproduced significantly more, in fruit substrates containing odors of adult flies and eggs rather than fruit substrates artificially inoculated with fly eggs. Our findings suggest that F. ceratitivorus is a promising new parasitoid for biological control of C. capitata in Hawaii.     

Evaluation of the fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes), a potential biological control agent of Lutzomyia longipalpis (Diptera, Psychodidae)

Visceral leishmaniasis is a zoonosis whose primary vector in Brazil is the sandfly Lutzomyia longipalpis Lutz & Neiva. Presently, efforts to control the vector have not been effective in reducing the prevalence of disease. A possible alternative to current strategies is the biological control of the vector using entomopathogenic fungi. This study evaluates the effects of the fungus, Beauveria bassiana (Bals.) Vuilleman, in different developmental stages of L. longipalpis. Five concentrations of the fungus were utilized ranging from 10⁴ to 10⁸ conidia/ml, with appropriate controls. The unhatched eggs, larvae and dead adults exposed to B. bassiana were sown to reisolate the fungus. The fungus was subsequently identified by polymerase chain reaction (PCR) and DNA sequencing. Exposure to B. bassiana reduced the number of eggs that hatched by 59% (P < 0.01). The longevity of infected adults was 5 days, significantly lower than that of the negative control which was 7 days (P < 0.001). The longevity of the adult sandfly exposed to the positive chemical (pyrethroid, cypermetherin) control was less than 1 day. The effects of fungal infection on the hatching of eggs laid by infected females were also significant and dose-dependent (P < 0.05). With respect to fungal post-infection growth parameters, only germination and sporulation were significantly higher than the fungi before infection (P < 0.001). The identity of the reisolated fungus was confirmed by automated DNA sequencing post-passage in all insect stages. These data show that B. bassiana has good pathogenic potential, primarily on L. longipalpis larvae and adults. Consequently, the use of this fungus in sandfly control programs has potential in reducing the use of chemical insecticides, resulting in benefits to humans and the environment.     

Interactions among the entomopathogenic fungus, Beauveria bassiana (Ascomycota: Hypocreales), the parasitoid, Aphidius matricariae (Hymenoptera: Braconidae), and its host, Myzus persicae (Homoptera: Aphididae)

The effect of the entomopathogenic fungus Beauveria bassiana on the biological characteristics and life table of Aphidius matricariae, a parasitoid of the green peach aphid, Myzus persicae, was studied under laboratory conditions. Aphids were first infected with twice the LC₉₅ of B. bassiana for third-instar M. persicae (2 × 10⁸ conidia/ml). Subsequently, at different intervals they were exposed to 1-day-old mated parasitoid females for 24 h. The number of mummies produced per female and the percentage emergence of the F1 generation differed significantly as a function of the time interval between application of the fungus and exposure to the parasitoid. The interference of B. bassiana on parasitoid development was also studied by first exposing the aphid hosts to the parasitoid for 24 h and subsequently applying B. bassiana. The number of mummies produced by a female A. matricariae varied from 11.8 to 24.8 and was significantly different when the aphids were first exposed to the parasitoids and then treated with B. bassiana 24, 48, 72, and 96 h after exposure. There were no significantly different effects of B. bassiana on net reproductive rate (R₀), mean generation time (T), intrinsic rate (r_m) and the finite rate of increase (λ) of A. matricariae as a result of development in hosts exposed to low or high conidial concentrations (1 × 10², 2 × 10⁸ conidia/ml). The parasitoids developed in infected hosts had lower r_m, λ, T and DT (doubling time) values compared with those that developed in uninfected hosts but no differences were observed in R₀ values. With proper timing, A. matricariae and B. bassiana can be used in combination in the successful biological control of M. persicae.     

Functional response of Neoseiulus barkeri Hughes on two-spotted spider mite (Acari: Tetranychidae)

Generalist predatory mites are the common phytoseiid fauna in many agroecosystems, but little attention has been paid to their potential as biological control agents. In this study, we determined the functional responses of adult females of the generalist predator Neoseiulus barkeri Hughes on eggs, larvae, and adults of the two-spotted spider mite, Tetranychus urticae Koch, in the laboratory. Predation experiments were conducted on pepper leaf discs over a 24 h period at 25±1°C, 70–80% RH and 16L:8D photoperiod. Prey densities ranged 5 to 80 eggs, or 5 to 40 larvae, or 1 to 8 female adults of T. urticae per disc. The predation rate of N. barkeri adult females on T. urticae eggs was the same as on its larvae, but the predation rate on adult females was much lower. The role of generalist predatory mites in integrated and biological control of greenhouse pests was discussed.     

Effects of temperature on development, survival, longevity, and fecundity of the Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) predator, Axinoscymnus cardilobus (Coleoptera: Coccinellidae)

Axinoscymnus cardilobus (Homoptera: Aleyrodidae) is an important predator of Bemisia tabaci (Coleoptera: Coccinellidae) that occurs in high population density of B. tabaci. Temperature among other factors is observed to play an important role in the development of arthropods. The effect of temperature on the development of A. cardilobus was studied at seven constant temperature regimes (14, 17, 20, 23, 26, 29, 32 °C). The results indicated that the duration of egg, larval and pupal stages were significantly influenced by increased temperature. The rate of development gradually increased with increase in temperature from 14 °C to 26 °C, but declined from 26 °C to 32 °C. The survival rates of different insect stages were stable at temperatures between 20 °C and 26 °C, but at extreme temperatures of 32 °C and 14 °C, a sharp decrease was evident. Ovipositional period of the female decreased when temperatures were increased from 17 °C to 32 °C. The highest fecundity of the female (225.7 eggs per female) was recorded at 23 °C. Life tables of A. cardilobus were constructed based on the experimental results at temperatures of 14–32 °C. The reproductive rate (R₀), the innate capacity for increase (r_m) and the finite rate of increase (λ) reached the maximum values at 23 °C, of 70.7, 0.059 and 1.062, respectively. The mean generation time (T) decreased with increased temperature from 17 °C to 32 °C, the highest and least values recorded at 17 °C and 32 °C were 112.7 and 38.7, respectively. These results offer valuable insight on the importation and establishment of A. cardilobus into new environments with diverse temperature regimes.     

Effect of temperature on survival, development and reproduction of the predatory lacewing Dichochrysa prasina (Neuroptera: Chrysopidae) reared on Ephestia kuehniella eggs (Lepidoptera: Pyralidae)

Preimaginal development and adult longevity and reproduction of Dichochrysa prasina Burmeister were studied at six constant temperatures (15, 20, 25, 27, 30 and 33 °C) and a photoperiod of 16:8 (L:D). Eggs of the flour moth Ephestia kuehniella (Zeller) were used as food throughout preimaginal development, whereas the adults of D. prasina fed on a liquid diet of water, yeast hydrolysate, sugar and honey. At the highest tested temperature of 33 °C no larvae completed their development. At the rest of the tested temperatures the egg to adult developmental period ranged from approximately 92 days at 15 °C to 25 days at 30 °C. Percentages of adult emergence ranged from 36% at 15 °C to 84% at 30 °C. Both adult longevity and fecundity were significantly affected by temperature and the intrinsic rate of increase (r_m) reached its maximum value at 27 °C. These results could be useful for the establishment of a small scale rearing and mass production of D. prasina.     

Comparative analysis of the reproductive biology of two Peristenus species (Hymenoptera: Braconidae), biological control agents of Lygus plant bugs (Hemiptera: Miridae)

Peristenus digoneutis Loan and Peristenus stygicus Loan, parasitoids of the European tarnished plant bug Lygus rugulipennis Poppius, are established in the United States for biological control of native North American Lygus species, and are being considered for deliberate release in Canada. High lifetime fecundity of parasitoids is considered a desirable attribute of biological control agents and therefore, an understanding of parasitoid reproductive biology is required. In the present study, the potential lifetime fecundity of both agents was compared under laboratory conditions to estimate the potential impact of Peristenus species on Lygus. Synovigenic P. digoneutis and P. stygicus females oviposited most actively in the first two weeks of their lifetime, with a maximum average daily oviposition rate after five days. The maximum number of eggs laid per day was 83 eggs for P. stygicus, and 36 eggs for P. digoneutis. P. digoneutis has an average potential lifetime fecundity of 385 ± 35 SE eggs produced over 22 ± 3 SE days. In contrast, P. stygicus females have a 50% higher mean potential lifetime fecundity reaching 782 ± 65 SE eggs over 28 ± 1 SE days. A positive correlation between lifetime fecundity and body size was found only for P. stygicus, and both species showed a significant relationship between lifetime fecundity and oviposition period. The present study demonstrates that the fecundity of P. digoneutis and P. stygicus is considerably higher than previously reported. Based on these findings, P. stygicus appears to be the most effective biological control agent for Lygus lineolaris (Palisot de Beauvois) when only fecundity is taken into consideration.     

Life history and demography of the predatory mite,Amblyseius longispinosus Evans

The life history and demography of Amblyseius longispinosus Evans were studied under laboratory conditions 25–28°C and 65–85% RH using the red form of the twospotted spider mite, Tetranychus urticae Koch complex as prey. The entire development from egg to adult averaged 102.5 h for both sexes with a survival rate of 90.0%. Immature females consumed more prey eggs than males, averaging 7.9 and 6.4 eggs/day, respectively. The embryonic development time for male eggs was longer (average 45.2 h) than for female eggs (average 42.6 h). The average duration of succeeding stages did not differ between the sexes: larva, 15.7; protonymph, 21.1; and deutonymph, 23.0 h. Larvae were not observed to feed. Statistically significant differences between sexes were noted with respect to consumption of the deutonymphs (female, average 4.0±0.2; male, average 2.9±0.3 eggs/day) but not of the protonymphs. Mating occurred on the same day as adult emergence and was repeated several times during the reproductive life. Egg laying started on the second day after emergence. Parameters relating to oviposition were: fecundity, gross (50.7) and net (43.3) eggs/female; hatchability, 99.6% (gross) and 99.5% (net); the oviposition lasted at most 28 days and showed a peak in the first week. Net reproductive rate (R₀) was 36.7 female offspring/female/generation time (T) of 9.0 days. The sex ratio was biased toward the females (71.9%), while the intrinsic rate of increase (r_m) was 0.4 with a doubling time (DT) of 1.7 days. Males lived longer (36 days) than females (30 days) with a LT₅₀ for males of 26 days and for females of 22 days.