Functional response of Chrysoperla carnea (Neuroptera: Chrysopidae) to Helicoverpa armigera (Lepidoptera: Noctuidae): Effect of prey and predator stages

Abstract Understanding predator–prey interactions has a pivotal role in biological control programs. This study evaluated the functional response of three larval instars of the green lacewing, Chrysoperla carnea (Stephens), preying upon eggs and first instar larvae of the cotton bollworm, Helicoverpa armigera Hübner. The first and second instar larvae of C. carnea exhibited type II functional responses against both prey stages. However, the third instar larvae of C. carnea showed a type II functional response to the first instar larvae of H. armigera, but a type III functional response to the eggs. For the first instar larvae of C. carnea, the attack rate on H. armigera eggs was significantly higher than that on the larvae, whereas the attack rate of the second instar C. carnea on H. armigera larvae was significantly higher than that on the eggs. For the third instar larvae of C. carnea, the attack rate on the larvae was 1.015 ± 0.278/h, and the attack coefficient on the eggs was 0.036 ± 0.005. The handling times of the third instar larvae on larvae and eggs were 0.087 ± 0.009 and 0.071 ± 0.001 h, respectively. The highest predation rate was found for the third instar larvae of C. carnea on H. armigera eggs. Results of this study revealed that the larvae of C. carnea, especially the third instar, had a good predation potential in controlling H. armigera eggs and larvae. However, for a comprehensive estimation of the bio‐control abilities of C. carnea toward H. armigera, further field‐based studies are needed.     

Host-stage preference and functional response of aphid parasitoid Diaeretiella rapae (McIntosh) (Hym.: Braconidae) on greenbug,Schizaphis graminum (Rondani) (Hem: Aphididae)

Searching capacity is of great importance in the efficiency of natural enemies. In this research, the host-stage preference and functional response of Diaeretiella rapae (McIntosh) to different densities of greenbug, Schizaphis graminum (Rondani) were determined on Pishtaz wheat leaves at 25 ± 1°C, 60–70% relative humidity, and a photoperiod of 16:8 h (L:D). The host-stage preference was investigated by exposing 60 number of all nymphal instars and adults of greenbug to individual parasitoid females at eight replicates. Results indicated significant preference of D. rapae to second instar nymphs of S. graminum to perform functional response experiment. Densities of 2, 4, 8, 16, 32, 50, 64, 90 and 130 second instar nymphs of greenbugs were exposed to individual mated female wasps at 10 replicates for 24 h. Type of functional response was determined by logistic regression and its parameters, searching efficiency (a) and handling time (T _h), were estimated by non linear regression. The results indicated that the functional response of D. rapae was type III and values of searching efficiency, handling time and maximum rate of parasitism were calculated by two models as 0.1364 ± 0.084, 0.5761 ± 0.0179, 41.6594; 0.06489 ± 0.00652 (h^?1), 0.5628 ± 0.0173 (h) and 42.6439 (aphids/parasitoid/day), respectively.     

Influence of intraguild predation between Episyrphus balteatus and Hippodamia variegata on their prey

Intraguild predation (IGP) is an interaction that frequently occurs in natural enemy communities, especially aphidophagous predators. This research investigated IGP intensity between Episyrphus balteatus De Geer (Diptera: Syrphidae), with Hippodamia variegata Goeze (Coleoptera: Coccinellidae). Five predator combinations including second and third larvae of H. variegata and third instar larvae of E. balteatus plus control treatment (totally six treatments) were tested. The effect of IGP on cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) population density was investigated on sweet pepper seedlings under laboratory microcosms. In most combinations, the third instar larvae of E. balteatus alone reduced an A. gossypii population more efficiently than ladybird larvae and their combinations. Furthermore, IGP between third instar of E. balteatus and second larvae of H. variegata was asymmetrical; second instar H. variegata larvae were always the intraguild prey for third instar E. balteatus. The obtained result showed that outcome of IGP interaction on cotton aphid density was non-additive.     

Development and functional response of Coelophora inaequalis (Coleoptera: Coccinellidae) feeding on brown citrus aphid, Toxoptera citricida (Homoptera: Aphididae)

1 Development and survivorship of Coelophora inaequalis (F.) were evaluated in the laboratory on the brown citrus aphid, Toxoptera citricida (Kirkaldy) at 20 and 25 °C. Coelophora inaequalis could complete its life cycle feeding on T. citricida at these two temperatures. The developmental period from egg to adult was significantly longer at 20 °C (24.7 d) than at 25 °C (15.9 d). The survivorship of combined immature stages were higher at 25 °C (39.2%) than at 20 °C (34.3%). 2 The effects of prey densities (4–64 aphids per leaf disk) on the functional responses of C. inaequalis fourth‐instar larvae and female adults were investigated using grapefruit leaf disks over a 24‐h period at 25 °C and a photoperiod of LD 14 : 10 h. Logistic regression analyses indicated that fourth‐instar larvae and adults exhibited a type II functional response to aphid density. Fourth‐instar larvae had a higher search rate (0.1305) than C. inaequalis female adults (0.0989). The handling time of fourth‐instar larvae (30.4 min) was significantly longer than that of female adults (5.8 min). Collectively, C. inaequalis appears to be a promising biological control agent of T. citricida in the citrus groves.     

Predation capacity and prey preference of <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> on <Emphasis Type="Italic">Pieris brassicae</Emphasis>

The predation capacity and prey preference of larvae of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) on eggs or larvae of Pieris brassicae (Linnaeus) (Lepidoptera: Pieridae) in the absence and presence of cabbage aphids as an alternative prey were evaluated in laboratory experiments at 25°C. Both instars preyed upon butterfly eggs and larvae as well as on cabbage aphids with the third instar being the most voracious. The lacewings had a strong preference for caterpillars to butterfly eggs. In the presence of the aphids the predation on P. brassicae eggs or larvae was either completely abandoned or reduced by about 70%, respectively, by second instar lacewings and either reduced by about 80% or maintained, respectively, by third instar lacewings. Both instars thus had a clear preference for aphids compared to eggs of P. brassicae. However, second instar lacewings preferred aphids to caterpillars whereas the opposite was the case for third instar lacewings. The results indicate that 3rd instar C. carnea has a potential as biocontrol agent against P. brassicae.     

Functional Response of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) to Sugarcane Whitefly Aleurolobus barodensis (Maskell) in Laboratory Conditions

A functional response study of Chrysoperla carnea (Stephens) larvae to different densities of sugar cane whitefly Aleurolobus barodensis (Maskell) was conducted in test tubes at 26?±?2 °C, 65?±?5 % RH. Chrysoperla carnea showed two different types of functional response in larval instars. First instar exhibits type II. However, second and third larval instars revealed type III functional response. Based on modified Holling’s disk equation, the highest searching rates (a) of 0.82?±?0.0247 h^?1 was found for first instar larva. For second and third larval instars, the attack coefficient (b) were 0.002?±?0.030 and 0.0025?±?0.0424 respectively. The shortest handling time (T_h) per prey was observed at third instar stage (1.574?±?0.0568 h) followed by second and first instar with 1.72?±?0.0411 h and 1.919?±?0.0568 h respectively.     

Foraging responses of Coccinella septempunctata,Hippodamia variegata and Chrysoperla carnea to changing in density of two aphid species

The successful use of predators in classical biocontrol programmes needs several background laboratory investigations, one of which is the evaluation of predator behavioural responses to changes in the density of their prey. The impact effect of the density of two prey species [Myzus persicae Sulzer and Aphis craccivora Koch (Hemiptera: Aphididae)] on the predation rates of third-instar Chrysoperla carnea Stephens (Chrysopidae: Neuroptera) and fourth-instar Coccinella septempunctata L. and Hippodamia variegata Goeze (Coccinellidae: Coleoptera) larvae was studied. Although prey species, predator species, prey density, and their interactions all had significant effects on the numbers of aphids consumed, the type of functional response did not vary, remaining a type II response in all treatments. However, the type II parameters differed among predator species on the same prey species, and for each predator species on the two prey species. Chrysoperla. carnea on M. persicae and H. variegata on A. craccivora were more voracious than other predators. In the context of functional response and biological control, the release of these predators, that show inverse density-dependent mortality, has to be started in early season to build up their population on low aphid densities and attack later high aphid populations.     

Cornicle secretions of Uroleucon nigrotuberculatum (Homoptera: Aphididae) as the last bullet against lady beetle larvae

Aphids have evolved various defense strategies against natural enemies, including secretions from their cornicles. We assessed the defensive function of cornicle secretions by the goldenrod aphid, Uroleucon nigrotuberculatum (Olive), against larvae of the lady beetles Coccinella septempunctata bruckii Mulsant and Propylea japonica (Thunberg) (Coleoptera: Coccinellidae). The aphid secreted red droplets from its cornicles when attacked by the larvae. Two‐thirds of the C. septempunctata bruckii larvae and 46.7% of the P. japonica larvae that preyed on the aphids died before reaching the pre‐pupal stage. The secretions caused molting failure when smeared on the larvae's heads or glued to the larvae's mouthparts, killing 56.7% of C. septempunctata bruckii larvae and 36.7% of P. japonica larvae. Second instar larvae were affected most. About 40% of third and fourth instar larvae of C. septempunctata bruckii vomited soon after ingesting the aphids. In the field, up to 40% of first and second instar larvae were smeared with red secretions. Our results show that these cornicle secretions are an effective and active defense against earlier instars of coccinellid larvae.     

Ontogenetic shifts in the functional response and interference interactions of Rhyacophila dorsalis larvae (Trichoptera)

1. Ontogenetic shifts in predator behaviour can affect the assessment of food‐web structure and the development of predator–prey models. Therefore, it is important to establish if the functional response and interference interactions differ between life‐stages. These hypotheses were tested by (i) comparing the functional response of second, third, fourth and fifth larval instars of Rhyacophila dorsalis, using three stream tanks with one Rhyacophila larva per tank and one of 10 prey densities between 20 and 200 larvae of Chironomus sp.; (ii) using other experiments to assess interference within instars (two to five larvae of the same instar per tank), and between pairs of different instars (one, two or three larvae per instar; total predator densities of two, four or six larvae per tank). 2. The first hypothesis was supported. The number of prey eaten by each instar increased with prey density, the relationship being described by a type II model. The curvilinear response was stronger for fourth and fifth instars than for second and third instars. Mean handling time did not change significantly with prey density, and increased with decreasing instar number from 169 s for fifth instars to 200 s for second instars. Attack rate decreased progressively with decreasing instar number. Handling time varied considerably for each predator–prey encounter, but was normally distributed for each predator instar. Variations in attack rate and handling time were related to differences in activity between instars, fourth and fifth instars being more active and aggressive than second and third instars, and having a higher food intake. 3. The second hypothesis was partially supported. In the interference experiments between larvae of the same instar or different instars, mean handling time did not change significantly with increasing predator density, and attack rate did not change for second and third instars but decreased curvilinearly for fourth and fifth instars. Interference between some instars could not be studied because insufficient second instars were available at the same time as fourth and fifth instars, and most third instars were eaten by fourth and fifth instars in the experiments. Prey capture always decreased with decreasing attack rate. Therefore, interference reduced prey consumption in fourth and fifth instars, but not in second and third instars. The varying feeding responses of different instars should be taken into account when assessing their role in predator–prey relationships in the field.     

Formulation and application of the entomopathogenic fungus: Zoophthora radicans (Brefeld) Batko (Zygomycetes: Entomophthorales)

Aims: To isolate and formulate a native strain of Zoophthora radicans naturally infecting larvae of diamondback moth, Plutella xylostella, existing in South Australia and to provide evidence that formulation of the fungus is effective against P. xylostella larvae, and therefore, it could be used as a tool in pest management of this insect. Methods and Results: Dose–response bioassays using formulated and unformulated forms of the fungus strain were carried out against third instar larvae of P. xylostella. Results obtained have indicated a significant increase in the larval mortality when higher concentrations of a formulated form of the fungus strain were applied compared to the treatments with the unformulated form (85·0 vs 57·5% of larval mortality, respectively, at the top concentration of 10⁷ conidia/ml). The median lethal concentration (LC50) for a formulated form was 100 times less than that of the unformulated form when they were applied against the third instar larvae of P. xylostella. In addition, the formulation used in the present bioassays has preserved the viability of introduced fungus conidia for longer time in comparison with the unformulated conidia. Conclusions: The effective application of a formulated fungus strain against P. xylostella larvae constitutes the first step towards its use in pest management of this insect. Significance and Impact of the Study: The formulated fungus in inverted emulsion could be used as an alternative tool to insecticides in pest management of P. xylostella larvae because of the development of resistance to insecticides in the treated larvae.     

Effectiveness of larvae ofSyrphus ribesii andS. Corollae [Diptera: Syrphidae] as predators onMyzus persicae [Homoptera: Aphididae]

Capture efficiency, handling time and functonal response to prey density were studied in larvae ofSyrphus ribesii (L.) andS. corrollae (Fabr.) eatingMyzus persicae Sulz. at 20°C, 16 hrs light. First instar larvae ofS. ribesii had distinctly higher capture efficiency than 1st instar larvae ofS. corollae, both versus 1st instar and adult aphids. Second and 3rd instar larvae of both species seemed to prefer adult rather than 1st instar aphids, but no distinct difference in capture efficiency between the species was found. On comparable stages,S. ribesii always had shorter handling time thanS. corollae and it appeared in both species to be correlated with size of prey and predator. Handling time was thus shortest when 3rd instar larvae consumed 1st instar aphids. During one hour, 3rd instar larvae ofS. ribesii consumed aphids in quantities almost linearly dependent on aphid density (5, 10, 20 and 40 adult aphids/100 cm²), although the response also could roughly be described byHolling's “basic functional response curve”. On the contrary, 3rd instar larvae ofS. corollae soon reached a maximum consumption during one hour, being almost constant (5–7 aphids) at prey densities ≥10 aphids/100 cm².

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Résumé L'efficacité prédatrice (proportion de toutes les rencontres entre larves de syrphes et pucerons se terminant par la capture et la succion de pucerons), la durée d'activité et la relation entre l'absorption de nourriture et la densité des proies (5, 10, 20 et 40Myzus persicae Sulz. aptères au 5^e stade larvaire/100 cm²) ont été étudiées chez des larves deSyrphus ribesii (L.) etS. corollae (Fabr.) à 20°C et 16 h de photopériode. Les L₁ deS. ribesii présentent une efficacité prédatrice des pucerons des premier et dernier stades nettement plus élevée que les L₁ deS. corollae (S. ribesii: 71 et 38%;S. corollae: 42 et 0%). Chez les larves des 2^e et 3^e stades, on n'a observé aucune différence d'efficacité prédatrice entre les 2 espèces, mais une préférence pour les pucerons adultes. La durée d'activité deS. ribesii est dans tous les cas plus courte que celle deS. corollae pour un même stade de larves et de pucerons. Une corrélation positive semble exister entre la taille des proies et celle des prédateurs. La durée d'activité est la plus courte pour des prédateurs en L₃ s'alimentant de pucerons au premier stade (1,3 mn chezS. ribesii et 2,3 mn chezS. corollae). L'absorption de nourriture enregistrée en une heure chezS. ribesii varie presque linéairement avec la densité des pucerons; elle correspond d'autre part assez bien à la formule deHolling. L'absorption de nourriture parS. corollae atteint un maximum de 7 pucerons à l'heure et demeure pratiquement constante à partir d'une densité≥10 pucerons/100 cm².

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The author wishes to thank techn. ass.Bodil Horgen for assistance during the experiments     

Predation by Podisus maculiventris (Hemiptera: Pentatomidae) on Plutella xylostella (Lepidoptera: Plutellidae) larvae parasitized by Cotesia plutellae (Hymenoptera: Braconidae) and its impact on cabbage

Biological control offers potentially effective suppression of the diamondback moth (DBM), Plutella xylostella, a serious pest of Brassica crops. Little is known of whether multiple natural enemies have additive, antagonistic, or synergistic effects on DBM populations. No-choice and choice tests were conducted to assess predation by Podisus maculiventris on DBM larvae parasitized by Cotesia plutellae and unparasitized larvae. In no-choice tests, P. maculiventris preyed on greater numbers of parasitized than unparasitized larvae and greater numbers of young larvae than old larvae. In choice tests with early third instar DBM, there was no difference in predation between parasitized or unparasitized larvae. However, in choice tests with older prey, P. maculiventris preyed on more parasitized than unparasitized larvae. Two field studies were conducted to test if this predator and parasitoid have additive, antagonistic or synergistic effects on DBM populations and plant damage in cabbage (Brassica oleracea var. capitata). In 2002, DBM populations were significantly lower in the presence of C. plutellae but not in the presence of P. maculiventris. There was not a significant interaction between the natural enemies. Plant damage was reduced only with C. plutellae. In 2003, DBM populations were significantly lower in the presence of C. plutellae and P. maculiventris, although the combination of natural enemies did not lead to a non-additive interaction. Plant damage was unaffected by the presence of either natural enemy. Because of its greater predation on parasitized larvae, P. maculiventris could be an intraguild predator of C. plutellae. Yet, their overall combined effect in the field was additive rather than antagonistic.     

Reciprocal intraguild predation between two mirid predators,Cyrtorhinus lividipennis and Tytthus chinensis (Hemiptera: Miridae)

Interactions between predator species shape ecological communities and are crucial in the relationship between biodiversity and ecosystem functioning. They contribute to improving the natural biological control. Cyrtorhinus lividipennis Reuter and Tytthus chinensis Stål (Hemiptera: Miridae) are important natural enemies of brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), the most destructive rice pest in Asia. Comparative functional responses of both sexes of the two mirids at different development stages were estimated and the direction, symmetry, as well as intensity of intraguild predation (IGP) were studied in the laboratory. Prey preferences of the two mirid species and the influence of alternative prey on functional responses were also evaluated. The mirids exhibited reciprocal IGP in addition to consuming eggs of BPH. All predator–prey combinations exhibited a type II functional response. Females and fourth instar nymphs of C. lividipennis showed greater voracity for eggs of BPH than of T. chinensis. The two mirids were more voracious to intraguild prey than to extraguild prey. Alternative prey released the functional responses of C. lividipennis to both intra- and extraguild prey. In contrast, alternative prey had no effect on the functional response of T. chinensis. RIGP was symmetrical in the absence of extraguild prey. And in the presence of extraguild prey that was common in the field, resulted in different responses by the mirids.     

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

Tuta 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.     

世界麦双尾蚜研究进展：防治方法和策略*

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), was a worldwide cereal pest. The control measures to this pest were reviewed, emphasizing on natural enemies and plant resistance. First, spring wheat with earlier planting dates had higher yield and could resist RWA infestation to a more extent, while winter wheat with later planting dates could escape infestation of Russian wheat aphid with very few exceptions. So, manipulation of wheat planting dates was suggested in worldwide scale for the aphid control. Second, the natural enemies were considered as the most important factor to reduced the pest status. Introduced and native natural enemies were evaluated for their potential as biological agents in South Africa, United States, and Australia. In South Africa, an introduced parasitoid and a predator were selected for releasing. In the United States, the project on exploring and releasing the natural enemies was unprecedented in biological control history. The endeavor in USA has been proved primarily successful today and will be afterward. The RWA control in Chile was considered most successful, partly because of their introduction of natural enemies before the aphid arrival. The native enemies together with other factors in central Asia and Europe apparently suppressed the aphids to a low level. The screen for resistant wheat was another important research project in fighting with RWA. In South Africa and USA, resistant wheat and barley were bred, and some of them had been put in commercial use for RWA control. The overwhelming mechanisms in resistant wheat varieties were antibiosis, tolerance or their combination. Though chemical insecticide spraying was proved as an effective method for aphid control, more and more research has switched from this method to non chemical control measures as required by IPM. Future research should put more emphasis on augmentation of the natural enemies, revealing the relationship between RWA and agricultural ecosystem and integration of all effective measures.     

Functional response and predation of Nabis kinbergii （Hemiptera. Nabidae） to Plutella xylostella （Lepidoptera. Plutellidae）

The functional response of adult Nabis kinbergii （Hemiptera： Nabidae） to density of diamondback moth Plutella xylostella （Lepidoptera： Plutellidae） was investigated under laboratory conditions. Holling＇ s （1959） type Ⅱ model was found to be a good fit for the observed functional response of this predator. The numbers of P. xylostella consumed increased with temperature from 15℃ to 35℃. The maximum number of prey killed was observed at 35℃, with average of 10.3 and 8.3 forth instar larvae consumed by adult females and males of N. kinbergii, respectively. The predation of N. kinbergii on P. xylostella increased with successive immature stages. The number of prey consumed by predators decreased as the body size of prey increased. An average of 131 eggs or 95 larvae of P. xylostella were killed by a single of female adult in 24 hours at 24＂C. The pupae of P. xylostella were observed to be eaten by fifth instar nymphs and adults N. kinbergiiin numbers of less than an average of 0.7 pupae per predator in 24 hours at 24＂C. Predation preference by N. kinbergii was also investigated. The number of P. xylostella and Myzus persicae killed by female N. kinbergii was not significantly different, but males killed significantly more P. xylostella than M. persicae. Both eggs and larvae of P. xylosteUa were killed in significantly greater number than those of Pieris rapae in the same feeding arena.     

不同农业景观结构对麦蚜种群动态的影响

研究表明农业景观结构的复杂性与害虫种群发生强度关系密切,然而在不同农业景观结构下研究麦蚜的发生、种群及寄生蜂的变化还不多。设计了不同的麦田景观结构,调查研究了不同麦田景观结构对麦蚜种群的影响。在简单与复杂两种农业景观结构下,分析了不同种类麦蚜的入田时间、入田量、种群增长率、种群密度及寄生性天敌的多样性与寄生率。结果表明:景观结构对不同种类麦蚜影响不同,但复杂农业景观下麦蚜迁飞入田时间都要晚于简单农业景观(连片种植)下的入田时间,复杂农业景观下有翅蚜的迁入量显著低于简单景观下有翅蚜的迁入量,并且复杂农业景观下麦蚜种群增长速率高于简单农业景观下的增长速率。不同种类麦蚜对景观结构的不同反应可能与形态学与生活史特征有关,两种不同农业景观结构下寄生性天敌的多样性与寄生率无显著差异。复杂景观结构下的麦蚜有翅蚜低的迁入量、高的增长速率可能与生境高度破碎化有关,其中与温室大棚塑料白色反光有的很大的影响。生境破碎化影响了麦蚜对寄主植物寻找以及天敌对猎物的寻找效应。     

Responses of Episyrphus balteatus DeGeer (Diptera: Syrphidae) in relation to prey density and predator size

Laboratory experiments were conducted to determine the functional and numerical responses of the aphidophagous hover fly Episyrphus balteatus DeGeer (Diptera: Syrphidae) to different densities of 4th instar black bean aphids, Aphis fabae Scopoli (Homoptera: Aphididae), on broad bean, Vicia faba L. (Fabaceae). Two different-sized larvae of predators were tested in different densities of similar-sized prey to determine whether functional response parameters depended on the body sizes of predator and prey. In numerical response experiments, gravid E. balteatus females were exposed individually to different densities of 4th instars of A. fabae on cut sections of the broad bean plant, V. faba L. Logistic regression suggested a type II functional response for both larval sizes of E. balteatus. The searching efficiency (a) of the larger larvae was higher than that of the smaller ones. Prey consumption was higher, and handling time (T_h) was lower for larger larvae than smaller ones. The theoretical maximum number of A. fabae nymphs eaten by the different-sized larvae was 125 and 269 nymphs per day. Larger E. balteatus larvae are more efficient predators for aphid management strategies. The reproductive numerical response, in terms of the number of eggs laid, increased curvilinearly with increasing prey density, but the proportion of eggs laid (egg number/prey density) decreased as the initial density of prey increased.     

Spatio‐temporal association of Therioaphis maculata and Hippodamia variegata in alfalfa fields

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Effect of cold acclimation and rapid cold-hardening on the survival of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) under cold stress

Spodoptera frugiperda is a highly invasive pest species that recently invaded Africa and Asia causing severe economic losses, primarily related to corn and rice crops. Temperature is one of the most important environmental factors that influence the invasion of pests into new habitats. However, little is known regarding the thermal tolerance characteristics of invasive S. frugiperda. Thus, we investigated the response of four developmental stages of S. frugiperda (i.e., eggs, third and sixth instar larvae, and pupae) to cold acclimation (CA) and rapid cold-hardening (RCH). All individuals suffered high mortality with 24-h temperature treatments at <?5°C and >35 °C. The CA treatment significantly increased the survival rate of the eggs and third instar larvae, although it did not affect the sixth instar larvae and it decreased the pupation rate. The RCH treatment at 5 °C for 5 h or 2 °C for 2 h increased the cold tolerance capabilities of the third and sixth instar larvae, respectively. Thus, the larval stage appears to be crucial for the cold tolerance of S. frugiperda. Our findings improve the current understanding of the cold tolerance characteristics of S. frugiperda and indicate its potential for survival in the newly invaded temperate regions of Asia.