The influence of feeding and host deprivation on egg load and reproduction of an aphid parasitoid, <Emphasis Type="Italic">Aphidius gifuensis</Emphasis> (Hymenoptera: Braconidae)

With a view to improving the establishment of Aphidius gifuensis Ashmead, a potential natural enemy for suppression of aphids on vegetables, the effects of host deprivation and honey feeding before release on the parasitoid’s egg load and reproduction were studied under laboratory conditions. Host deprivation significantly affected mummy production and survival rate of female parasitoids. A. gifuensis produced more mummies when exposed to a short period (1 and 2 days) of host deprivation, but when host deprivation lasted for 3 days, their mummy production sharply decreased. Offspring produced by parasitoids that had been deprived of hosts for 2 days were much heavier than those produced by parasitoids deprived of hosts for 1 and 3 days. However, host deprivation did not affect emergence rate or offspring sex ratio; the emergence rate was always above 80%, and the offspring sex ratio was always female biased irrespective of whether the host-deprivation period was 1, 2, or 3 days. Honey feeding greatly increased egg load, longevity and decelerated oosorption of A. gifuensis when hosts were absent, and significantly increased parasitoid mummy production in late age. We discuss the results in the context of augmentative biological control, with the view to understanding how to increase parasitoid performance after they are released.     

Effects of feeding frequency and sugar concentrations on lifetime reproductive success of Meteorus pulchricornis (Hymenoptera: Braconidae)

Many species of parasitoids can increase their reproduction through feeding on supplemental sugar sources. We evaluated the longevity both with and without hosts and progeny production of a uniparental strain of Meteorus pulchricornis by varying concentration of the sugar solution and feeding frequency. A 1:1:1 sucrose–glucose–fructose-mixture was tested in a range of concentrations (0–70% (w/v)). The parasitoid lifespan did not increase with the concentration of sugar solutions, but parasitoids feeding on a 30% sugar solution attained greater longevity than parasitoids feeding on other sugar concentrations in the absence of hosts. The same effect of sugar concentration was also observed on progeny production, where when the parasitoid was fed 30% (w/v) sugar solution, its lifetime progeny production doubled in comparison to that fed water, and increased by 50% compared to those fed the other sugar solutions. In the last experiment, we studied the effect of feeding intervals on the longevity and progeny production of M. pulchricornis. Parasitoids fed with a 30% (w/v) 1:1:1 sucrose–glucose–fructose-mixture continuously lived six times longer than unfed parasitoids, three times longer than parasitoids fed only once and two times longer than parasitoids fed once every two days in the absence of hosts. Parasitoids with continuous access to the sugar solution produced considerably more progeny than those with fewer feeding frequencies. This increasing progeny production was accomplished more through an increase in daily offspring production rather than through extending reproductive lifespan.     

Development and reproduction of a potential biological control agent, Aphelinus varipes (Hymenoptera: Aphelinidae), at different temperatures

The development and reproductive potential of an indigenous parasitoid, Aphelinus varipes (Förster), was studied at 15, 17, 20, 25, and 30 °C. Developmental durations decreased with increasing temperatures. The emergence rate was higher than 90 % at 15, 17, and 20 °C. Offspring sex ratios were 0.69, 0.54, and 0.70 at 17, 20, and 25 °C, respectively, but were 0.14 at 15 °C and 0.38 at 30 °C. Developmental zeros of females and males were calculated as 9.9 and 9.6 °C, respectively. The effective accumulative temperature (K) was 204.1 degree-days in both sexes. Fecundity peaked in early age after emergence, then gradually decreased in a fluctuating manner at 20 and 25 °C. Host feeding continued constantly during the life of female adults at two temperatures. Single female parasitoids produced 218.5 and 203.1 mummies at 20 and 25 °C, respectively, during their lifespans. Aphids killed by parasitoid host feeding numbered 79.1 at 20 °C and 63.8 at 25 °C. Longevities were 27.0 days at 20 °C and 20.6 days at 25 °C. Moreover, intrinsic rates of natural increase (r _m) were estimated as 0.151 at 20 °C and 0.227 at 25 °C. We discuss the potential of A. varipes as biological control agents by comparing them with Aphidius colemani Viereck, which has been introduced to horticultural crops in greenhouses in Japan.     

Effect of low temperature on emergence, fecundity, longevity and host-feeding by Trichogramma brassicae

The occurrence of sub-optimal temperatures during development of immature parasitoids can have important consequences on adult fitness. We investigated the impact of different regimes of low temperature on emergence, differential mortality, longevity and fecundity in Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae). The host-feeding behaviour of adult females was also measured as an indicator of energy reserve at emergence. Acclimation of 30 days at 10 °C or 24 days at 13 °C allowed T. brassicae immatures to develop with a lower mortality than those exposed directly at 5 °C. Longevity and fecundity of females decreased at a lower rate with acclimation at 10 °C suggesting that acclimation at 13 °C may have depleted the energy reserves of individuals more than acclimation at 10 °C. Short photoperiod exposure during the maternal generation had no effect on progeny’s fitness. We found no difference among the treatments in females’ host-feeding behaviours, in differential mortality at emergence, in female’s mobility and in F1 sex ratio.     

Effect of six carbohydrate sources on the longevity of a whitefly parasitoid Eretmocerus hayati (Hymenoptera: Aphelinidae)

Parasitoid adults often acquire carbohydrates by feeding on floral nectar and honeydew which provides them with energy and prolongs their life span. The concentration and type of saccharide in nectar and honeydew are variable by species of plant and insect. To explore the effects of various sugar type and concentrations on parasitoid fitness, we compared 5%, 10% and 20% (w/v) solutions of six different sugar resources (glucose, fructose, sucrose, trehalose, melezitose and honey) on the longevity of Eretmocerus hayati, a larval parasitoid of the whitefly Bemisia tabaci in China. Male and female longevity was increased by all of the sugar diets, but female wasps survived longer than the males when the same sugar diet was supplied. Female parasitoids feeding on 10% glucose and 10% honey increased longevity, respectively up to 6.2- and 5.9-fold longer than distil water; 5% honey and 10% fructose had the greatest effects on male longevity, up to 3.5- and 3.3-fold. All six sugar diets, no matter which concentration, significantly changed the survival curves. Glucose, sucrose and honey were optimal sugar diets for this wasp, and 10% was the optimal concentration. Our results could provide an insight into the nutritional requirements of E. hayati under laboratory conditions. Such information can be a basis to improve the longevity of this biological control agent by sugar feeding during the indoor mass-rearing process.     

Effects of host larval stage preferences and diet on life history traits of Diadegma mollipla,an African parasitoid of the Diamondback Moth

Knowledge of the biological attributes of parasitoids plays a fundamental role in improved management of their pest hosts. Diadegma mollipla is a major indigenous parasitoid of the Diamondback Moth (DBM), Plutella xylostella (Linnaeus), in Eastern Africa. Two laboratory experiments were conducted to determine the DBM larval stage preferences of D. mollipla and their influence on life history traits and the effect of different diets (20% honey, 20% sugar solution, water or nothing) on adult parasitoid longevity. In the first study, 60 DBM larvae (15 each of larval stages L1–L4) were exposed to either one adult parasitoid female or four competing females in choice experiments. When DBM larvae were exposed to one parasitoid, in terms of parasitism, L1 and L2 were found to be the most preferred stages, followed by L3 and then L4. Sex ratio (females/males) increased with host larval stage from 1.3 to 3.1. Pre-imaginal development time was longer in L1 than in the other three stages. When exposed to four parasitoids, no significant differences in parasitism rates and progeny production were obtained between DBM larval stages. However, sex ratio increased from 0.8 in L1 to 4.1 in L4. Developmental time was longest in L4, intermediate in L1 and L3, and shortest in L2. In the diet experiment, honey and sugar were found to significantly increase longevity for D. mollipla adults of both sexes. Overall, combined adult male and female longevity was 24.5, 9.9, 2.2 and 1.9 days when fed on honey, sugar, water or nothing, respectively.     

Effect of different dietary resources on longevity, carbohydrate metabolism, and ovarian dynamics in two fruit fly parasitoids

A growing body of literature reports the importance of non-prey food sources in boosting fitness of arthropod natural enemies, thus further contributing to their pest control efficacy. Although resources such as nectar, pollen, or honeydew have received a fair amount of research attention, little is known about the role of fruit juices. Under natural conditions, Tephritid fruit fly parasitoids enjoy ample access to fallen or damaged fruits and their saccharide-rich juices, and wasp fitness can potentially benefit in multiple ways from access to these resources. In this study, we compared the effect of fruit juice with other food resources on multiple fitness parameters in parasitoids that commonly forage on fallen, damaged fruits: the braconid Diachasmimorpha longicaudata and figitid Aganaspis pelleranoi. Parasitoids were subject to simple or combined diets of guava juice (Psidium guajava), honey and pollen, and their effect on wasp longevity, ovarian dynamics and (body) carbohydrate levels was assessed. For both species, adult longevity proved lowest on simple diets of water, guava juice, or pollen, while greatest longevity was attained on honey or combined diets. For D. longicaudata, egg load did not differ between the various diets, while A. pelleranoi egg load was higher for individuals that had access to honey or pollen, but did not differ between newly emerged wasps and those fed guava juice. In both parasitoid species, total sugars, fructose, and glycogen levels were highest in wasps fed with honey or combined diets and lowest under (simple) guava juice, pollen, or water diets. In conclusion, D. longicaudata and A. pelleranoi attained superior longevity and body nutrient levels with access to high-sucrose sugar sources, such as honey, but benefited comparatively little from access to guava juice. Our work hints the role of high-sucrose foods such as (extra-) floral nectar or artifical sugar sprays in boosting fitness of fruit fly parasitoids. We further discuss the relevance of these findings for fruit fly biological control, in crops such as guava.     

Incomplete control of the diamondback moth,Plutella xylostella,by the parasitoid Cotesia vestalis in a cabbage field under tropical conditions

Immature Plutella xylostella (Lepidoptera: Plutellidae) and parasitoids were sampled for 39 months in an unsprayed cabbage field near Cotonou, Benin, to determine how and when host-parasitoid interactions influence the population dynamics of the moth in a tropical environment. Eighty-three samples were taken at approximately two-week intervals. There were no seasonal patterns in the abundance of immature moths, which was not correlated with weather variables, although heavy rainfall during the principal rainy season may have temporarily affected the population. The host-parasitoid system consisted almost exclusively of P. xylostella and its larval parasitoid Cotesia vestalis (Hymenoptera: Braconidae), both species occurring at similar levels of abundance (on average 7.5 ± 0.3 and 7.2 ± 0.3 individuals per plant, respectively). The tendency for host-parasitoid dynamics to cycle was apparent in the field. P. xylostella and C. vestalis showed coupled oscillations in abundance, with a time lag of about two weeks between host and parasitoid peaks. High parasitoid abundance resulted in significant decreases in moth abundance over several weeks. However, the parasitoid population in turn decreased, could not prevent the moth from rebounding, and there was no stable control of the pest. We conclude that under tropical conditions in which P. xylostella populations grow rapidly, combined with a high probability of recolonization from surrounding areas, biological control by a well-established specialist parasitoid reaches its limits and additional control measures are necessary.     

Lifespan and patterns of accumulation and mobilization of nutrients in the sugar-fed phorid fly, Pseudacteon tricuspis

Abstract. The effect of sugar feeding on the survival of adult phorid fly Pseudacteon tricuspis is investigated. Flies fed 25% sucrose in aqueous solution continuously throughout their lifespan have greater longevity (mean ± SE longevity: female = 7.9 ± 0.8 days, male = 8.9 ± 0.9 days) than completely starved (provided no water and no sugar solution) flies, sugar-starved (provided water only) flies, or flies fed sugar solution only on their first day of adult life. Completely starved flies rarely lived beyond one day. Provision of water increases longevity by 2 days, and one full day of sugar feeding further increases longevity by an additional 1–2 days. Flies fed 50% sucrose have similar survivorship as those fed 25% sucrose. The temporal patterns of nutrient accumulation and utilization are also compared in P. tricuspis fed different diets: sugar-starved, sucrose-fed on the first day of adult life only, and sucrose-fed continuously. Adult P. tricuspis emerge with no gut sugars, and only minimal amounts of body sugars and glycogen. Although the levels of body sugars and glycogen decline gradually in sugar-starved flies, a single day of sugar feeding results in the accumulation of maximum amounts of gut sugars, body sugars and glycogen. High levels of these nutrients are maintained in female and male phorid flies fed on sucrose continuously over the observation period, whereas nutrient levels decline in flies fed only on the first day of life, beginning 1 day postfeeding. Female and male P. tricuspis emerge with an estimated 12.3 ± 2.3 and 7.2 ± 1 g of lipid reserves per fly, respectively. These teneral amounts represent the highest lipid levels detected in adult flies, irrespective of their diet, and are maintained over the life times of sucrose-fed female and male flies, but declined steadily in sugar-starved females. These data suggest that adult P. tricuspis are capable of converting dietary sucrose to body sugars and glycogen, but not lipids.     

Lifetime gains and patterns of accumulation and mobilization of nutrients in females of the synovigenic parasitoid, Diglyphus isaea Walker (Hymenoptera: Eulophidae), as a function of diet

In nature, adult parasitoids feed to obtain and use nutrients for supplementing and/or replenishing some of their existing array of nutrient reserves. When adults feed on host or non-host food, they can enhance fitness, typically by increasing egg production or longevity. In the present study, ovigeny index (OI) and impact of female fitness, as well as physiological state on the reproductive strategies, were investigated in the synovigenic parasitoid, Diglyphus isaea, fed on host food (2-3rd instars of Liriomyza sativae larvae), non-host foods (10% honey solution) and starved (distilled water, control). The results showed that D. isaea was a strongly synovigenic parasitoid, of which OI value was 0.002. Both types of food enhanced the fecundity and prolonged the longevity of the females. D. isaea females fed on non-host food showed higher levels of gut sugar, body sugar and glycogen than those fed on host food, but the levels of lipid were higher in the host-fed females. D. isaea females seemed to show lipogenesis, with low rates of lipid catabolism sufficient to satisfy the requirement of egg maturation. Females might absorb lipids directly from the haemolymph of paralyzed hosts.     

Effect of cold storage of adult Trichogramma brassicae,T. cacoeciae and T. evanescens (Hym.: Trichogrammatidae)

Abstract

Trichogramma cacoeciae Marchall, T. brassicae Bezdenko and T. evanescens Westwood could be useful in biological control programmes of agricultural insect pest. The possibility of storing adult Trighogramma species at low temperatures, and the effect of such storage on the quality of the parasitoids and its fecundity were studied. Trighogramma cacoeciae, T. brassicae and T. evanescens adults were stored for 1, 2, 3, 4 and 5 days at 4 ± 1°C in a refrigerator, 60 – 70%RH and full darkness. Storage at 4 ± 1°C reduced fecundity and longevity of female parasitoids.     

The influence of hosts, temperature and food sources on the longevity of Trichogramma platneri

Feeding experiments were conducted with Trichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) reared from the Angoumois grain moth, Sitotroga cerealella (Oliver) (Lepidoptera: Gelechiidae). T. platneri provisioned with host eggs do not live any longer than T. platneri without host eggs. Longevity of T. platneri is inversely related to temperature declining from 53 days at 10 °C to 3 days at 35 °C for honey-fed parasitoids and from 9 days at 10 °C to 1 day at 35 °C for unfed parasitoids. Sugar sources are necessary to prolong longevity of T. platneri, but a source of amino acid did not promote longevity. Honey solutions greater than 10%, and 43% fructose and sucrose solutions increased longevity 10–13 fold to 15–20 days in comparison to water when fed daily to T. platneri. Parasitoids fed only at the onset of the trial had greater longevity than unfed parasitoids but had a shorter longevity than parasitoids fed daily, due to the evaporation of the sugar solutions and consumption of the honey. Aphid honeydew is a suitable field-available sugar source supporting longevity up to 10 days, but is not as good as other sugar sources. Stabilizing additives did not reduce evaporation of a dilute sugar solution nor prolong longevity of T. platneri. Simulating a daily dew fall by misting vials, to redissolve the crystallized food residues left after providing food at the onset of the trial, failed to increase parasitoid longevity.     

Development and parasitization of an aphid’s secondary parasitoid,Dendrocerus laticeps (Hymenoptera: Megaspilidae), on Aphidius colemani (Hymenoptera: Braconidae)

Banker-plant systems using Aphidius species have been employed to control pest aphids in greenhouses growing eggplant and sweet pepper in Japan. However, a strong negative correlation between the occurrence of secondary parasitoids and aphid-control success by this system was reported by Nagasaka et al. (2010). To control secondary parasitoid populations, detailed knowledge of their ecological characteristics is needed. In this paper, the development and parasitization ability of Dendrocerus laticeps (Hedicke) (Hymenoptera: Megaspilidae), a major secondary ectoparasitoid of Aphidius species in Japan, were examined under 25 °C laboratory conditions. The maximum female longevity was about 11 days when honeydew was available. Parasitization occurred only on mummified aphids, and the age of mummified aphids did not influence the ecological value of offspring. The maximum parasitization ability was 18.9 hosts/day estimated by Holling’s disc equation. Possible lifetime fecundity was 100.35. The intrinsic rate of natural increase estimated by the bootstrap method ranged from 0.211 to 0.321, depending on the assumptions made about larval mortality. The countermeasures for avoiding the negative impacts of D. laticeps in a banker-plant system include the development of a refuge for mummified aphids and increasing the temperature around the banker plants.     

Plant Resistance Affects the Olfactory Response and Parasitism Success of Cotesia vestalis

Understanding the factors influencing host-selection behavior of parasitoids is essential in studies on host-parasitoid ecology and evolution, and in combining sustainable strategies of pest management, such as host-plant resistance and biological control. The effects of host-plant resistance on the olfactory response and parasitism success by Cotesia vestalis, a parasitoid of diamondback moth (Plutella xylostella) larvae were examined. Here, it was demonstrated that host-plant resistance can strongly influence foraging behavior and parasitism success of the parasitoid. In olfactometer experiments, C. vestalis did not differentiate between crucifer plant types with similar levels of susceptibility or resistance to P. xylostella but showed a strong preference for susceptible compared with partially-resistant host plants. The influence of previous oviposition activity varied with the host-plant type experienced by the parasitoid. In cage experiments, C. vestalis preferred to parasitize P. xylostella larvae on a susceptible plant compared with larvae on a partially resistant host plant when exposed to hosts for 24 h. However, this preference appeared to be transitory, and was not found after 96 h exposure. The present study suggests that combining partial host-plant resistance with biological control by C. vestalis for the control of P. xylostella may in some circumstances be antagonistic and negatively affect parasitism success.     

Effects of Five Naturally Occurring Sugars on the Longevity,Oogenesis, and Nutrient Accumulation Pattern in Adult Females of the Synovigenic Parasitoid Neochrysocharis formosa (Hymenoptera: Eulophidae)

Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae), one of the dominant natural enemies of agromyzid leafminers, is a synovigenic parasitoid. We compared the longevity, oogenesis, and nutrient levels of female wasps provided with 10% solutions of five naturally occurring sugars. All five sugars significantly increased the longevity of female wasps, which was 6.5–9.3-fold higher than that of parasitoids provided with water only. We found no significant difference in longevity of female wasps fed on glucose versus fructose or trehalose versus melezitose, but longevity of wasps fed on glucose or fructose was significantly longer than those fed on trehalose or melezitose. Also, we examined the oosorption capability of wasps fed on the five sugars. Some mature eggs were present in the ovaries of newly emerged females, but these were fully reabsorbed within 72 h when wasps were starved. Once wasps were fed with any of the sugars, the number of mature eggs increased at first and then decreased due to oosorption. The longevity and oogenesis dynamics of female wasps fed on five sugars were related with their function of hydrolysis and digestion. As female wasps have no lipogenesis capability, by acquiring exogenous sugars for oogenesis, they can either maintain or exceed the original level of capital nutrients held on adult emergence because none of the wasps’ glycogen need be metabolized to burn as sugar.     

Comparing floral nectar and aphid honeydew diets on the longevity and nutrient levels of a parasitoid wasp

We compared the effects of floral nectar from buckwheat, Fagopyrum esculentum Moench, and honeydew produced by the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), on longevity, nutrient levels, and egg loads of the parasitoid Diadegma insulare Cresson (Hymenoptera: Ichneumonidae). Diadegma insulare lived for 2 days in control treatments of water or clean soybean leaves, for 6–7 days with honeydew, and in excess of 2 weeks with buckwheat nectar. Potential reasons for the superiority of buckwheat nectar over soybean aphid honeydew for extending the longevity of parasitoids include: (i) parasitoids ingest more sugars from floral sources, (ii) oligosaccharides in honeydew have a lower nutritional value than nectar sugars, and (iii) honeydew has antagonistic compounds. Overall sugar levels were lower in honeydew‐ vs. nectar‐fed female wasps, suggesting a lower feeding rate, but other explanations cannot be excluded. Diadegma insulare eclosed with high levels of lipids and glycogen, and low levels of gut and storage sugars. All carbohydrates increased over the life of both nectar‐ and honeydew‐fed wasps, but remained low or decreased in starved wasps. Lipid levels declined over the lifespan of female wasps, but females fed floral nectar showed the slowest rate of lipid decline. Diet did not affect egg load, probably because the females were not given hosts in the experiment.     

Effect of host feeding on life history traits of <Emphasis Type="Italic">Tamarixia radiata</Emphasis>, parasitoid of the Asian citrus psyllid, <Emphasis Type="Italic">Diaphorina citri</Emphasis>

The parasitoid Tamarixia radiata (Hymenoptera: Eulophidae) is being used for the biological control of the Asian citrus psyllid (ACP), Diaphorina citri (Hemiptera: Liviidae). The parasitoid is strongly synovigenic, as it is born with very few mature eggs. Synovigenic insects need to feed on host haemolymph to mature additional eggs, and are able to resorb mature eggs to allocate resources toward maintenance. We investigated the effect of host feeding on parasitism, longevity and egg load dynamics, and estimated egg maturation and resorption rates. Although host feeding does not increase survival or longevity, it results in increased parasitization rates when parasitoids are seven days old, and that a single host meal leads to an average gain of three eggs. We discuss the importance of these data to predict the foraging and parasitization behavior of T. radiata in the field, and to potentially improve current efforts to control ACP.     

Dietary sugars and amino acids increase longevity and enhance reproductive parameters of Bracon cephi and B. lissogaster,two parasitoids that specialise on wheat stem sawfly

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is a major pest of wheat grown on the Northern Great Plains and Canadian Prairies of North America, causing economic losses of as much as $350 million annually. Two species that parasitize wheat stem sawfly larvae in wheat stems are Bracon cephi (Gahan) and B. lissogaster Muesebeck (Hymenoptera: Braconidae). Carbohydrate-rich diets increase adult parasitoid longevity and reproductive parameters, enhancing their success as natural enemies. In previous studies, these species had increased longevity, egg load, and volume when fed sucrose solutions, encouraging further research on their nutritional needs. Therefore, we conducted experiments with artificial diets using adult females fed sucrose, glucose, and fructose solutions. Females were also fed these sugars in combination with a mixture of amino acids. We assessed individuals daily for longevity. Both species benefited from diets containing carbohydrates, with an increase in longevity from an average of 9 to 51 days for B. cephi, and from 6 to 34 days for B. lissogaster. Additional experiments assessed egg load and volume after 2, 5, and 10 days of cumulative feeding in B. cephi. These females produced 1.4-fold more eggs when fed amino acids, 2.5-fold more with sugar, and 2.7-fold more when fed sugar with amino acids. They had a 1.3-fold increase in egg volume when fed amino acids, 1.9-fold with sugar, and 2.1-fold when fed sugar with amino acids. Our study reveals the nutritional requirements of these braconid parasitoids and the benefits of nutritional sources when implementing conservation biological control strategies.     

Sugar‐feeding behaviour and longevity of European Culicoides biting midges

Most haematophagous insect vectors can also use sugar as an energy source; thus their sugar‐feeding behaviour influences their longevity and blood‐feeding rate and hence their vectorial capacity. Scant information is available on the sugar‐feeding behaviour of Culicoides Latreille biting midges (Diptera: Ceratopogonidae), which are vectors of bluetongue and Schmallenberg viruses. The longevity of laboratory‐reared Culicoides nubeculosus (Meigen) under fluctuating temperatures (16 and 28 °C) and with access to water or water and blood was on average 6.4 days and 8.9 days, respectively, which was around one third of the lifespan of siblings with access to sugar or sugar and blood (22.2 days and 27.1 days, respectively). Access to honeydew significantly increased the midge's longevity, whereas the provision of extrafloral nectaries had no impact. Females with access to sugar produced a significantly higher number of eggs (65.5 ± 5.2) than their starved sisters (45.4 ± 8.4). More than 80% of field‐caught female Culicoides from the two most abundant European groups, Obsoletus (n = 2243) and Pulicaris (n = 805), were fructose‐positive. Fructose‐positivity was high in all physiological stages and no seasonal variability was noted. The high rate of natural sugar feeding of Culicoides offers opportunities for the development of novel control strategies using toxic sugar baits and for the monitoring of vector‐borne diseases using sugar‐treated FTA (nucleic acid preservation) cards in the field.     

Life Cycle of Tetranychus macfarlanei Baker and Pritchard (Acari: Tetranychidae): A New Pest of Medicinal Plants in West Bengal

The life cycle of Tetranychus macfarlanei Baker and Pritchard was studied on two different medicinal plants, Clitoria ternatea L. and Justicia adhatoda L. Nees, in BOD at 32.5 °C and 75 % RH during April 2007 to May 2007. Observations towards duration of different stages like egg, larva, protonymph, deutonymph, adult, total life cycle, preoviposition, oviposition, postoviposition periods, longevity of female and male, and fecundity, sex ratio were recorded. Total developmental period of T. macfarlanei from egg to adult was 6.4 ± 0.37 (Mean ± SE) and 10.6 ± 0.56 days on C. ternatea and J. adhatoda, respectively. On C. ternatea, the fecundity in case of fertilized and unfertilized female were 91.6 ± 11.61 and 80 ± 21.64 eggs, respectively and longevity of fertilized and unfertilized female was 16.4 ± 1.44 and 8.6 ± 2.32 days, respectively. The corresponding figure on J. adhatoda for fecundity in case of fertilized and unfertilized female were 39 ± 2.85 and 19.8 ± 3.90 eggs, respectively and for longevity was 16 ± 0.37 and 11 ± 086 days, respectively. Among the two hosts, C. ternatea appears to be more preferred to J. adhatoda because life cycle was completed in shorter time and fecundity and female longevity were for longer duration.