Preimaginal Developmental Time Research Articles

Larval development and voracity of Eupeodes americanus (Diptera: Syrphidae): comparison of the focal prey Aphis gossypii (Hemiptera: Aphididae) and the banker prey Rhopalosiphum padi (Hemiptera: Aphididae).

Unlike European species, the potential of Nearctic syrphids as biological control agents is still poorly studied. However, the American hoverfly, Eupeodes americanus (Wiedemann), has recently demonstrated promising traits as a biocontrol agent, notably against the foxglove aphid, Aulacorthum solani Kaltenbach, on pepper. The present study aims to extend our knowledge of the American hoverfly by evaluating its potential as a biocontrol agent in a banker plant system against the melon aphid, Aphis gossypii Glover, in a greenhouse cucumber crop. The preimaginal development and voracity of E. americanus were compared when preying upon the focal prey/pest (A. gossypii) or the banker prey (bird cherry-oat aphid, Rhopalosiphum padi L.) by daily observations of larvae from egg to adult. Preimaginal development time, survival rate, and occurrence of deformation were similar on both prey species. The weight of third instar and pupae, however, washigher for larvae that fed on the banker prey. The ad libitum voracity of the syrphid larvae was generally very high and did not significantly differ between prey species, except for the third-instar larvae which consumed more focal prey. Results suggest that a banker plant system involving the bird cherry-oat aphid may be a promising tactic for utilizing E. americanus for melon aphid biocontrol.

Laboratory evaluation of Ooencyrtus obscurus (Mercet) (Hymenoptera: Encyrtidae) on Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) eggs

Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae), known as the western conifer seed bug (WCSB), is a significant pest of the Pinus pinea L. kernel sector in the Mediterranean basin. The egg parasitoid species Ooencyrtus obscurus (Mercet) (Hymenoptera: Encyrtidae) has been recently recorded on WCSB eggs in Central Spain. This study defines the influence of the egg cluster size on the parasitism rate of O. obscurus, its reproductive and demographic parameters with the goal of defining the potential of this species to be a biological control agent. Ooencyrtus obscurus is weakly synovigenic, with the parasitism period concentrating in the first two weeks, reaching its maximum level of intensity on the 1st day (30.2 %). The mean oviposition period was 2.3 days, with the mean female longevity being 16.9 days. The mean rate of pre-imaginal survival was high (96.7 %), with the mean pre-imaginal development time being significantly higher for females than for males. The sex ratio (% females) was 41.2 %, while the reproductive strategy was defined as being pseudo-arrhenotokous parthenogenesis after comparing mated and unmated female offspring. Regarding demographic parameters, a single O. obscurus female was able to produce more than 3 female offspring (R0) in a generation time (T) of 23.96 days, multiply its population 1.05 times a day (λ), and double it in 14.34 days (Td). The comparison between these results and those established for the main egg parasitoid of the WCSB in its native area could allow for decisions to be made on the type of biological control program to be applied in Europe.

Is Fopius arisanus (Hymenoptera: Braconidae) a suitable biological control agent of Bactrocera dorsalis (Diptera: Tephritidae) in multi-crop orchards?

In the present study, we investigated the bottom-up effects of four economically important host fruit species (guava, mandarin orange, plum, pear) on Bactrocera dorsalis parasitoid Fopius arisanus in terms of emergence, parasitism, sex ratio, developmental duration, longevity and body size. Our results showed that F. arisanus reared on guava infested with B. dorsalis had highest emergence, parasitism, sex ratio and longevity, while these parameters were lower on B. dorsalis-infested mandarin orange. Moreover, body size of F. arisanus (wing, hind tibia and body lengths for both sexes and ovipositor length for female) varied significantly among the B. dorsalis-infested fruits, with mandarin orange providing the biggest emergent body size for both sexes and guava providing the smallest. The shortest preimaginal developmental time for both sexes was in infested plums and the longest in infested mandarin orange. Therefore, we inferred that B. dorsalis-infested guava is the most suitable host–host plant combination for F. arisanus fitness among the tested fruit-host combinations. Our findings corroborates that the ability of some tested fruit species to serve for the permanent establishment of F. arisanus in the field, which will aid in boosting the efficiency of F. arisanus as a biological control agent, especially in multi-crop orchards.

Development cycle of a potential biocontrol agent: the American hoverfly, Eupeodes americanus, and comparison with the commercial biocontrol agent Aphidoletes aphidimyza

AbstractAphids (Hemiptera: Aphididae) are a major economic problem in numerous crops, including pepper, melon, and potato. Larvae of the American hoverfly, Eupeodes americanus (Wiedemann) (Diptera: Syrphidae), are common aphidophagous natural enemies in agrosystems in North America. The objective of the present study was to characterize the development cycle of E. americanus in order to evaluate its potential as a biocontrol agent. The development cycle, survival rate, and adult longevity of E. americanus were determined and compared with those of the commercial aphid midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) under laboratory conditions, using the green peach aphid, Myzus persicae (Sulzer), as prey. The complete preimaginal development time, pupal development time, egg hatching rate, sex ratio, and survival rate were not different between E. americanus and the commercial A. aphidimyza. The larval developmental time was longer in the syrphid species, increasing the predation window. Finally, the adult longevity of the syrphid was drastically longer than that of A. aphidimyza. These results demonstrate a potential for E. americanus as a new aphidophagous biocontrol agent.

Coexistence and intraguild competition of Chrysomya albiceps and Lucilia sericata larvae: case reports and experimental studies applied to forensic entomology

The larval development of Chrysomya albiceps and Lucilia sericata is a well-known and valuable tool for estimating the postmortem interval (PMI). The third instar larvae of Ch. albiceps are facultative predators of the larvae of other necrophagous dipterans, and this behaviour is undoubtedly an important factor to consider. Both species are found together during human autopsies in Spain and other parts of Europe, where they cohabit, so a precise knowledge of their larval coexistence data is essential. The aim of this study is to investigate their coexistence and the intraguild predation of Ch. albiceps on L. sericata under experimental conditions and in real case reports. To analyse intra- and interspecific competition, four densities were used under controlled abiotic conditions [25ºC, 60-70% RH and 12:12 (D:N)]. The experimental data were compared with data corresponding to their coexistence in natural conditions, so annual activity and forensic case reports for both species were studied. The results indicate that the mortality of immature specimens in both species, the preimaginal developmental time, and adult size were affected by competition. In natural conditions, adult coexistence during the spring-summer period was confirmed. The simultaneity of the two species colonising human corpses is frequent in the studied area, with Ch. albiceps being the dominant species, and L. sericata the relevant species for estimating the minimum postmortem interval.

Insecticide resistance exerts significant fitness costs in immature stages of Anopheles gambiae in western Kenya

BackgroundDespite increasing documentation of insecticide resistance in malaria vectors against public health insecticides in sub-Saharan Africa, there is a paucity of information on the potential fitness costs of pyrethroid resistance in malaria vectors, which is important in improving the current resistant management strategies. This study aimed to assess the fitness cost effects of insecticide resistance on the development and survival of immature Anopheles gambiae from western Kenya.MethodsTwo-hour old, first instar larvae (L1) were introduced and raised in basins containing soil and rainwater in a semi-field set-up. Each day the number of surviving individuals per larval stage was counted and their stage of development were recorded until they emerged as adults. The larval life-history trait parameters measured include mean larval development time, daily survival and pupal emergence. Pyrethroid-resistant colony of An. gambiae sensu stricto and susceptible colony originating from the same site and with the same genetic background were used. Kisumu laboratory susceptible colony was used as a reference.ResultsThe resistant colony had a significantly longer larval development time through the developmental stages than the susceptible colony. The resistant colony took an average of 2 days longer to develop from first instar (L1) to fourth instar (L4) (8.8 ± 0.2 days) compared to the susceptible colony (6.6 ± 0.2 days). The development time from first instar to pupa formation was significantly longer by 3 days in the resistant colony (10.28 ± 0.3 days) than in susceptible colony (7.5 ± 0.2 days). The time from egg hatching to adult emergence was significantly longer for the resistant colony (12.1 ± 0.3 days) than the susceptible colony (9.6 ± 0.2 days). The pupation rate (80%; 95% (CI: 77.5–83.6) vs 83.5%; 95% (CI: 80.6–86.3)) and adult emergence rate (86.3% vs 92.8%) did not differ between the resistant and susceptible colonies, respectively. The sex ratio of the females to males for the resistant (1:1.2) and susceptible colonies (1:1.07) was significantly different.ConclusionThe study showed that pyrethroid resistance in An. gambiae had a fitness cost on their pre-imaginal development time and survival. Insecticide resistance delayed the development and reduced the survivorship of An. gambiae larvae. The study findings are important in understanding the fitness cost of insecticide resistance vectors that could contribute to shaping resistant management strategies.

Provision of astigmatid mites as supplementary food increases the density of the predatory mite Amblyseius swirskii in greenhouse crops, but does not support the omnivorous pest, western flower thrips

Astigmatid mites can be used as prey for mass rearing of phytoseiid predators, but also as a supplemental food source to support predator populations in crops. Here we evaluated the potential of six species of astigmatid mites (living or frozen) as alternative food for the predatory mite Amblyseius swirskii Athias-Henriot in greenhouse crops. All prey mites tested were suitable for predator oviposition. In general, oviposition was greater when prey mites were reared on dog food with yeast than when they were reared on wheat bran with yeast. Amongst prey items provided as frozen diet, larvae of Thyreophagus entomophagus (Laboulbene), Acarus siro L. and Lepidoglyphus destructor (Schrank) that had been reared on dog food with yeast, resulted in the highest oviposition rates of A. swirskii. T. entomophagus larvae as frozen diet resulted in the shortest preimaginal developmental time of A. swirskii. On chrysanthemum plants, we found that the greatest increase in predator density occurred when living mites of T. entomophagous were used as a food source. This increase was greater than when predators were fed cattail pollen, a commonly used supplemental food. Effects on predators of providing living A. siro and L. destructor, or frozen larvae of T. entomophagous as food, were comparable with provision of pollen. Use of supplemental food in crops can be a risk if it is also consumed by omnivorous pests such as western flower thrips, Frankliniella occidentalis Pergande. However, we showed that both frozen and living mites of T. entomophagous were unsuitable for thrips oviposition. Hence, we believe that provision of prey mite species increases A. swirskii density, supporting biological control of thrips and other pests in greenhouse crops.

Preimaginal developmental time of two egg parasitoids and their host searching efficiency

ABSTRACTWhen searching for hosts, parasitoids may experience competition between adults exploiting the same host (extrinsic), or between larvae developing inside the host (intrinsic competition). Differences in competitive abilities like host location and resource utilisation promote coexistence. In this sense, extrinsically superior parasitoids better locate hosts, and intrinsically superior ones can have a shorter preimaginal development, which gives them a competitive advantage in physiological suppression against its competitor. Piezodorus guildinii (Hemiptera: Pentatomidae) is an important soybean pest, and its main natural enemies are egg parasitoids Telenomus podisi and Trissolcus urichi (Hymenoptera: Platygastridae). We compared the ability of wasps to locate host eggs, and larval development time of both parasitoids. Both species took the same amount of time to find and contact eggs, and to start parasitising them. There were no differences in average development time of larvae, pupae, and the entire preimaginal period. Both parasitoid species compared in this study are closely related, having very similar life history strategies. These factors could have covered up other aspects of the host foraging abilities of each species, which can make differences between them when searching for hosts in the field. Moreover, searching abilities of both species could be similar under laboratory conditions but different under field conditions. Understanding competitive interactions between parasitoids is important to improve the biological control of the pest.

Compatibility between the endoparasitoid Hyposoter didymator and the entomopathogenic fungus Metarhizium brunneum: a laboratory simulation for the simultaneous use to control Spodoptera littoralis.

The cotton leafworm, Spodoptera littoralis, is one of the most destructive pests in the Mediterranean basin, being predominantly controlled using synthetic chemical pesticides. Strain EAMa 01/58-Su of the fungus Metarhizium brunneum and the parasitoid Hyposoter didymator are promising biological control agents for this pest. In this study, we assessed the compatibility between these two agents to control S. littoralis under joint attack scenarios. Firstly, the direct and indirect effects of the fungus towards parasitoid adults were studied. The fungus significantly decreased life expectancy of the parasitoid (mortality=62.5%; mean lethal concentration=1.85 × 106 conidia ml-1 ; average survival time=92.2h) when applied at high concentrations (108 conidia ml-1 ), whereas it did not affect the reproductive potential of the parasitoid females during the 3 days after treatment. Secondly, the combinations between the two agents to control S. littoralis under different simultaneous use scenarios (inoculation of S. littoralis larvae with the fungus before being exposed to parasitoid females and vice versa) were investigated, with additive effect in all cases. A significant effect on fitness (preimaginal development time and reproductive potential) of the F1 parasitoid generation were detected. Moreover, parasitization significantly reduced the total hemocytes in S. littoralis hemolymph compared with the control, promoting fungal infection. Finally, parasitoids showed a significant preference for non-inoculated S. littoralis larvae. We demonstrated compatibility (additive effect) between fungus and parasitoid under different joint attack scenarios to control S. littoralis in laboratory conditions. However, this will be supported by our ongoing greenhouse and field studies. © 2019 Society of Chemical Industry.

Fruit Preference, Parasitism, and Offspring Fitness of Fopius arisanus (Hymenoptera: Braconidae) Exposed to Bactrocera dorsalis' (Diptera: Tephritidae) Infested Fruit Species.

Fopius arisanus (Sonan) (Hymenoptera: Braconidae) is a koinobiont solitary parasitoid of various fruit flies, particularly those in the genus Bactrocera. Researchers introduced F. arisanus into Africa for the biological control of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), a pest of a wide range of fruit trees and vegetables. However, the suitability of host fruit species as egg-laying substrates for parasitoid development remains poorly investigated in tropical Africa. The present study examines the preference and performance of F. arisanus on B. dorsalis reared on eleven fruit species through laboratory choice-test trials. We assessed the oviposition activity, parasitism rate, developmental time, and offspring fitness of F. arisanus on nine cultivated and two wild host fruits species. Oviposition attempts were higher on Psidium guajava (L.) (Myrtales: Myrtaceae) and Mangifera indica (L.) (Sapindales: Anacardiaceae) than on the other host fruits tested. The wasp parasitized host eggs in P. guajava in no-choice experiments. Psidium guajava, Irvingia wombulu (Vermoesen) (Malpighiales: Irvingiaceae), and Irvingia gabonensis (Aubry_Lecomte) Baill (Malpighiales: Irvingiaceae) were suitable for parasitism in choice tests. Of all host fruits tested, the body and hind tibia lengths of both parasitoid sexes emerging from M. indica were longer than on the others. The female ovipositor was long on Annona squamosa (L.) (Magnoliales: annonaceae) and short on Eribotrya japonica ([Thunb.] Lindl.; Rosales: Rosaceae). We obtained the longest preimaginal developmental time for both sexes on E. japonica and the shortest for females and males on Carica papaya (L.) (Brassicales: Caricaceae). These results demonstrate the ability of some tested fruit species to serve for the permanent establishment of F. arisanus in the field.

Assessment of the developmental success of Anopheles coluzzii larvae under different nutrient regimes: effects of diet quality, food amount and larval density

BackgroundIn a context of increasing resistance of both vectors toward main classes of insecticides used in public health and parasites toward anti-malarial drugs, development of new and complementary molecules or control approaches is fundamental to achieve the objective of controlling or even eliminating malaria. Concerning vector control, the sterile insect technique and other genetic control approaches are among promising complementary tools in an integrated management strategy for malaria control. These approaches rely not only on a good understanding of vector biology (especially during larval stages), but also on the availability of adequate supplies and protocols for efficient mosquito rearing. The aim of this study was to assess the factors impacting the life history of Anopheles coluzzii mosquitoes at the larval stage, in the context of genetic and sterile insect approaches to control malaria vectors.MethodsThe effect of different larval diets and larval rearing densities on the development of An. coluzzii were evaluated in the laboratory. Emergence rate (ER), pre-imaginal developmental time (DT) and adult wing length (WL) were measured under different food regimes. Four diets were tested among which three were provided by the Insect Pest Control Laboratory (IPCL) of the FAO/IAEA Joint division.ResultsData showed significant differences in the quality of the different diets and suggested a negative density dependence in all three life history parameters measured under tested rearing conditions. ER and WL increased with food availability, but decreased with increasing larval density. Conversely DT was shortened with increasing food availability but increased with larval density. These data demonstrates intraspecific larval competition modulated by food amount and space availability. Of the four diets tested, the one made of a mix of tuna meal, bovine liver powder, brewer’s yeast, squid liver powder and vitamin mix (diet 2) yielded the best results as it produced a good balance between ER, DT and WL. Food availability for optimal development (highest survival at shortest time) was in the range of 180–400 µg/larvae/day for the three diets provided by the IPCL.ConclusionThere is an interaction between diet type, diet concentration and larval density. Best results in terms of optimal larvae development parameters happen when moderately high values of those three variables are observed.

Morphological and biological characterization of a light-colored mutant in the multicolored Asian lady beetle, Harmonia axyridis.

Insect cuticle color formed with melanin pigments has numerous types of mutants which usually cause pleiotropic effects. Melanism has been widely studied, but mutants with light‐colored phenotype as well as the consequent fitness changes have rarely been reported.Here, in the laboratory strain of Harmonia axyridis, we found a novel mutant gr and confirmed that the mutation was inherited in a simple Mendelian autosomal recessive manner. This mutant (HAM) continuously displayed a light‐colored pigmentation versus dark blackish in the wild phenotype (HAW). L‐DOPA and dopamine are melanin precursors, and less L‐DOPA was present in the cuticle of larval and adult HAM mutants compared to HAW wild type, but more dopamine was detected in the larval cuticle of HAM (p ≤ 0.0235). For the orange background of elytra, the composition as well as total concentration of carotenoids was different between HAM and HAW, which resulted in significantly lower saturation value but significantly higher hue value in HAM than in HAW (p < 0.0001).Extensive fitness changes were detected in HAM. (a) HAM larvae had similar predation capacity and preimaginal development time as HAW, but the newly emerged adults were much smaller (p < 0.0001). (b) Both fecundity and egg hatch rate in cross ♀(HAM) × ♂(HAM) were significantly lower than those in ♀(HAW) × ♂(HAW) (p ≤ 0.0087), but were not different with those in ♀(HAW) × ♂(HAM). (c) HAM had weaker resistance to desiccation and ultraviolet irradiation compared to HAW (p ≤ 0.0115).These results indicated that the novel light‐colored mutant (HAM) was highly correlated with fitness changes, and it would be a perfect model to study molecular mechanisms of melanism and how a gene results in pleiotropic effects.

Predatory behavior of Synthesiomyia nudiseta larvae (Diptera: Muscidae) on several necrophagous blowfly species (Diptera: Calliphoridae)

Intraguild interactions play a prominent role in sarcosaprophagous communities, so intraspecific and interspecific competition phenomena between fly larvae take place. Synthesiomyia nudiseta is a species that has recently been recorded on human corpses in Europe, and it has been cited in forensic cases in Spain and Italy. The mature larvae are known to be facultative predators on necrophagous fly larvae, but their role as predators is unknown. The aim of this paper is to investigate the predatory behavior of S. nudiseta on the most abundant blowfly larvae in sarcosaprophagous communities in southwestern Europe (i.e., Chrysomya albiceps, Lucilia sericata, and Calliphora vicina). Intraspecific and interspecific competition experiments were carried out to study the effect of this species in the necrophagous diptera community. First-instar larvae were placed in plastic cups with the same amount of pig liver (15g) at different densities (50, 100, 150, and 300 individuals/cup). Mortality in blowflies increased when S. nudiseta larvae were present: up to 98.40% in Ch. albiceps, 89.60% in L. sericata, and 84.93% in C. vicina. Pre-imaginal developmental time and adult wing size were analyzed and compared under each of the intraspecific and interspecific conditions; both variables were affected by competition in all cases. The implications of the presence of S. nudiseta for sarcosaprophagous community dynamics and its effect on the estimation of postmortem interval (PMI) are discussed.

Reciprocal indirect interactions between Tetranychus urticae and Aphis gossypii mediated by cucumber plant

Abstract Induced plant responses to herbivory can alter plant quality and influence subsequent interactions with organisms that use that plant as food source. In this study, we conducted several experiments in order to understand whether preference and performance of the cotton aphid, Aphis gossypii (Hem: Aphididae) and the spider mite, Tetranychus urticae (Acari: Tetranychidae) are affected by the previous herbivory of conspecific or heterospecific species on cucumber plants. Longevity, fecundity and pre-imaginal development time were measured as performance criteria. In addition, we explored whether these effects are local or systemic. In the case of performance experiments, the results varied from negative to neutral depending on the performance criteria, no positive effect was observed in studied interactions. Also, depending on performance criteria, the previous herbivory affected the plant systemically, or locally. Results of preference experiments indicated that mites and aphids prefer to settle and produce offspring on control leaf disc to prevent detrimental effects of the previous herbivory. Spider mites showed a stronger preference than aphids in the detection of induced leaf discs, which resulted in more mites being present and laying more egg on control leaf disc in both local and systemic treatments. Performing both preference and performance experiments, not only reveals the effect of herbivores on each other's mediated by the plant but also reveals more information about the sensitivity of herbivores to change in the quality of their host.

Biology and performance of two indigenous larval parasitoids on Tuta absoluta (Lepidoptera: Gelechiidae) in Sudan

ABSTRACTTuta absoluta is an alien invasive pest in Sudan. Since it was detected in the country, the pest continues to cause major tomato losses. Alarmed by its devastating nature and the speed of spread, tomato growers resorted to the indiscriminate use of broad-spectrum insecticides. Promising indigenous parasitoid(s) may contribute to suppression of this pest. The biology and performance of the native parasitoids, Bracon nigricans Szépligeti (Braconidae) and Dolichogenidea appellator (Telenga) (Braconidae), was therefore evaluated against different immature stages of T. absoluta under laboratory conditions. A significantly higher number of fourth instar larvae was accepted for oviposition by B. nigricans. Similarly, fourth instar larvae yielded a considerably higher number of parasitoid offspring compared to third instar larvae. The male ratio of B. nigricans offspring which emerged from both larval instars was high, 0.96 and 0.66 for third and fourth instar larvae of T. absoluta, respectively. There was, however, no significant difference in the number of males and females that emerged from fourth instar larvae. Conversely, the number of hosts killed by stinging behaviour or host feeding was significantly higher on third instar larvae. B. nigricans potential fecundity varied with the age of the wasp with the lowest fecundity on the day of eclosion. The performance of D. appellator in terms of the total number of offspring produced and female progeny was similar for second and third instar larvae of T. absoluta. The preimaginal developmental time for both parasitoid species did not vary with either host stage or sex of the parasitoid. B. nigricans adult longevity was similar for both sexes, while that of D. appellator significantly varied with females living longer than males. Prospects for conservative biological control of T. absoluta are discussed in the light of the results of this study.

A β-carotene-amended artificial diet increases larval survival and be applicable in mass rearing of Harmonia axyridis

Artificial diets that devoid of insect components have been widely developed for predatory insects, but often yield disappointing results. Carotenoids play vital roles in insects and generally must be acquired from diet, but their supplementation in insect artificial diets has been rarely concerned. Here, we tried to evaluate the function and application prospect of carotenoids in artificial diet of Harmonia axyridis. Firstly, the physical form of component pork liver in artificial diet was improved using fine powder to replace the homogenate, and the survival of infant larvae was greatly increased. Then, four β-carotene-amended artificial diets were developed (0, 0.3, 3 and 30 μg/g (β-carotene/pork liver powder), indicated as AD-A, AD-B, AD-C and AD-D respectively) to evaluate their feeding efficiency for H. axyridis, and the aphid Myzus persicae was used as control. The larval survival on AD-D was equal to that on aphids, and was significantly higher than those on other artificial diets. However, H. axyridis feeding on artificial diets, whichever of the concentration of β-carotene, had significantly longer pre-imaginal development time and obtained smaller newly emerged adults than those on M. persicae. Overall, AD-D showed to be the optimal diet. Finally, the performance of AD-D-fed H. axyridis was evaluated on the target pest M. persicae. Compared to aphid-fed lady beetles, the fourth instar larvae raised with AD-D had similar number of aphid consumption and both showed preference for non-parasitized aphid than newly parasitized by Aphidius gifuensis; the adults produced fewer eggs but had undifferentiated pre-ovipostion period and egg hatch rate.In conclusion, supplementation of β-carotene could increase the efficiency of artificial diet. On M. persicae, H. axyridis developed from AD-D had outstanding performance which was applicable for releasing in biological control. Our results highlight the importance of carotenoids in artificial diet and might provide a new approach for developing artificial diets.

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

ABSTRACTKnowledge 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 some diets on biological parameters of Apomyelois ceratoniae in laboratory and efficiency of natural pheromone traps in pomegranate orchards

Pomegranate fruit moth (PFM), Apomyelois ceratoniae Zeller is a major pest of pomegranate in Iran. In this study, the effect of four diets including pistachio, pomegranate, semi-artificial and artificial diets were studied on biological parameters of PFM in a growth chamber under controlled conditions at 30 ± 2 °C, 65 ± 5% RH and 16:8 (L: D) h. The results demonstrated that the longest incubation period, larval developmental time and preimaginal development time was observed on artificial diet and the shortest was on the pomegranate. The highest and lowest body length of fifth instar larvae were observed on pistachio and artificial diet, respectively. The heaviest weight of third day pupae was recorded for the larvae that were reared on pistachio (0.0275 ± 0.0004 g) while the lightest was on artificial diet (0.0216 ± 0.0004 g). In the next experiment, the effect of four diets was considered to assess the efficiency of pheromone traps in a twenty year old pomegranate orchard cultivated with Malasse Yazdi cultivars. The effect of food on catch of traps showed a significant difference. The virgin PFM that were fed with pomegranate attracted more males. Also the traps caught the males mostly from 11:00 pm until 4:00 am, with the peak time between 23:00 and midnight. No significant difference was seen between diet and time of catch, indicating that starting or ending time and the maximum time of catch was not affected by the diets.

Modelling development of Callosobruchus maculatus and Anisopteromalus calandrae at various constant temperatures using linear and non-linear models

The development of cowpea weevil, Callosobruchus maculatus (Fabricius) (Col., Bruchidae), and its parasitoid, Anisopteromalus calandrae (Howard) (Hym., Pteromalidae), under nine constant temperatures and the best linear and non-linear models describing the temperature-development relationships of the host and its parasitoid were determined. The pre-imaginal developmental time decreased with increasing temperature from 15° C to 35° C for both species and sexes. Based on the best-fitted linear model, the lower developmental threshold and the thermal constant were determined as 10.4° C and 526.3 degree-days for C. maculatus and 11.5° C and 263.2 degree-days for A. calandrae, respectively. Fifteen non-linear temperature-dependent models were examined to find the best model to describe the relationship between temperature and development rate of C. maculatus and A. calandrae. Among non-linear models, the Analytis model was the most efficient for the description of temperature-dependent development of C. maculatus and A. calandrae.

Biology of Tupiocoris cucurbitaceus (Hemiptera: Miridae), a predator of the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) in tomato crops in Argentina

The predator Tupiocoris cucurbitaceus is frequently found attacking Trialeurodes vaporariorum in greenhouses without pesticide applications in Argentina. The objective of these studies was to evaluate some biological characteristics of this species fed on three types of diet (whitefly nymphs, Sitotroga cerealella eggs and a mix of both) and on two host plants (tomato and tobacco), under controlled experimental conditions. Preimaginal developmental time for female and male bugs was shorter in the presence of whiteflies than with only moth eggs. Females lived longer when they ate only whitefly nymphs compared to a mixed diet or only moth eggs. The amount of adult descendants was greater when bugs could eat whiteflies, regardless of the presence of S. cerealella. Embryonic development time, male longevity and sex proportion were not affected by the diet or the host plant. Prey consumption was evaluated for three T. cucurbitaceus life history stages (fourth/fifth instar nymphs, female and male adults) on two types of prey (whitefly nymphs and S. cerealella eggs). On tomato, females were more voracious than males and nymphs. On tobacco, adults and nymphs consumed more S. cerealella than T.vaporariorum nymphs, but again, bug females preyed more than males and nymphs. Results demonstrate that T. cucurbitaceus can survive, develop and reproduce normally using both T. vaporariorum and S. cerealella eggs as prey on tobacco or tomato plants. This information can be useful for managing this predator against T. vaporariorum through conservative or augmentative biological control strategies.