The performance of Oomyzus sokolowskii (Hymenoptera: Eulophidae) parasitizing Plutella xylostella (Lepidoptera: Plutellidae) on different host plants

Oomyzus sokolowskii Kurdjumov is a larval endoparasitoid of the diamondback moth, Plutella xylostella L., which is one of the most destructive pests of cruciferous vegetables worldwide. The performance of O. sokolowskii parasitizing P. xylostella on cauliflower (Brassica oleracea var. botrytis), Chinese cabbage (Brassica pekinensis), pakchoi (Brassica chinensis), cabbage (Brassica oleracea var. capitata), and broccoli (Brassica oleracea var. italica) was determined under laboratory conditions. Our results showed that O. sokolowskii performed best on cauliflower compared with the others, with the greatest net reproductive rate (R _o = 34.99), intrinsic rate of increase (r _m = 0.196), offspring emerged/host larva (9.0), percentage of parasitized host larvae with adults emerged (67.6 %), adults produced (43.6/female), and the shortest developmental time from egg to adult (15.8 days). Chinese cabbage-, pakchoi-, cabbage-, and cauliflower-adapted O. sokolowskii performed the best in percentage of parasitized host larvae with adults emerged, offspring adults produced per female, and offspring produced per host larva when parasitizing fourth instar P. xylostella larvae on cauliflower. The percentage of host-adapted female O. sokolowskii parasitizing different host-adapted fourth instar P. xylostella larvae was similar. Based on our results, we suggest that O. sokolowskii had performed best on cauliflower, which might be the best host plant to rear O. sokolowskii.     

Reproductive attributes of the eulophid Oomyzus sokolowskii,a biological control agent of diamondback moth,Plutella xylostella (Lepidoptera: Plutellidae)

Oomyzus sokolowskii (Kurdjumov) is a gregarious larval-pupal parasitoid of the diamondback moth, Plutella xylostella L. Under laboratory conditions, we explored the reproductive attributes including the functional response of O. sokolowskii and the impact of mutual interference among female parasitoids on progeny production and progeny sex ratio. In the functional response experiment, groups of 1–50 late instar larvae were exposed to groups of five female parasitoids for 48 h. Both Holling's disc equation (type II response) and Williams and Martinez's model (type III response) fit significantly better than the null-model assuming density-independent parasitation efficiency. Williams and Martinez's model was only marginally better than Holling's disc equation which explained 82% of the variation in the number of parasitized hosts. According to Holling's disc equation, the estimated maximum number of hosts parasitised during 48 h was 17 per group of five parasitoids, the estimated attack efficiency of a single female parasitoid (a) was 0.0024 larvae per hour, and the estimated handling time of a single female (T _h) was 14.4 h per host. In the mutual interference experiment 50 host larvae were exposed to different numbers of female parasitoids (P=5, 10, 20, 30, 40 and 50) for 48 h. With increasing numbers of conspecifics, the proportion of male progeny increased and total number of progeny per parasitoid decreased, yielding an estimated mutual interference constant (m) (±SE) of 0.95±0.14. The total number of wasps emerging from individual host pupae increased with increasing number of conspecifics. The age-specific fecundity of O. sokolowskii was investigated by providing 10 host larvae daily to individual female parasitoids. After 3 days of oviposition, 90% of the females were still alive and had achieved 76.4% of their lifetime fecundity. The proportion of female progeny decreased with female age. No relationship was found between female longevity and lifetime fecundity. The results suggest that parasitoid and host densities influence the progeny production and sex allocation strategy of O. sokolowskii. The information obtained from this study would help to develop a mass-rearing protocol for O. sokolowskii.     

Seasonal development and variation in abundance among four annual flight periods in a butterfly: a 20‐year study of the speckled wood (Pararge aegeria)

Insects typically spend the winter in a species‐specific diapause stage. The speckled wood butterfly, Pararge aegeria, is unique in having two alternative diapause stages, hibernating as larvae or pupae. In southern Sweden this creates a seasonal flight pattern with four annual adult flight periods: the first in May (pupal diapause), the second in June (larval diapause), and the third and fourth directly developing offspring generations in July and August, respectively. We address the raison d'être of the two diapause pathways by (1) outdoor rearing of cohorts, and (2) performing transect censuses throughout the season for 20 years. We contend that an early start of next season provides a benefit accruing to pupal diapause; conversely, a large proportion of the offspring from adults of the fourth flight peak are unable to reach the pupal stage before winter, providing a benefit accruing to larval winter diapause. The results obtained show that the two hibernation pathways are unlikely to be genetically distinct because of a strong overlap between the two offspring generations, and because sibling offspring from the third and fourth flight periods are likely to choose either of the two hibernation pathways, thereby resulting in a genetic mixing of the pathways. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 635–649.     

Acetaminophen at Different Doses Protects Brain Microsomal Ca2+-ATPase and the Antioxidant Redox System in Rats

Acetaminophen, an analgesic and antipyretic drug, rescues neuronal cells from mitochondrial redox impairment and reactive oxygen species (ROS). Excessive administration of acetaminophen above the recommended daily dose range has some negative effects on the brain. We investigated the effects of different doses of acetaminophen on Ca²⁺-ATPase and the antioxidant redox system in rats. Seventy rats were randomly divided into seven equal groups. The first was used for the control. One dose of 5, 10, 20, 100, 200, and 500 mg/kg acetaminophen was intraperitoneally administered to rats constituting the second, third, fourth, fifth, sixth, and seventh groups, respectively. After 24 h, brain cortical samples were taken and brain microsomal samples were obtained by ultracentrifugation. Brain and microsomal lipid peroxidation (LP) and brain calcium levels in the sixth and seventh groups were increased compared to control. LP levels in the second, third, and forth groups; brain vitamin E levels; brain and microsomal glutathione peroxidase (GSH-Px); and Ca²⁺-ATPase activity in the sixth and seventh groups were lower than in control, although brain vitamin E concentrations in the second, third, fourth, and fifth groups and microsomal GSH-Px activity in the third and fourth groups were higher than in control. Brain cortical β-carotene and vitamin A concentrations did not differ in the seven groups. In conclusion, 5–100 mg/kg acetaminophen seems to have protective effects on oxidative stress-induced brain toxicity by inhibiting free radicals and supporting the antioxidant redox system.     

Interaction of Acronicta rumicis (Lepidoptera: Noctuidae) and its larval parasitoid, Glyptapanteles liparidis (Hymenoptera: Ichneumonidae)

As a result of parasitism by Glyptapanteles liparidis in the first, second, third and fourth instar larvae of Acronicta rumicis, the mortality of each larval stage was found to be 46.67, 90, 71 and 16.67%, respectively. The mortality was highest when G. liparidis parasitized the second and third instar larvae. The difference in mortality between the parasitized group and the control group was 72.14% in the second instar larvae. With regards to the food consumption of the parasitized larvae, the first and second instar larvae consumed 6495.58 ± 646.52 mm² (leaf surface) and 7951.12 ± 4167.36 mm², respectively, while the third and fourth larvae consumed 13 826.77 ± 3396.66 mm² and 18 599.85 mm², respectively, showing that food consumption increased with instar stages of the host larvae. The clutch size of G. liparidis increased in relation to the instar stages of the host: it was 25.25 ± 7.89, 48.65 ± 53.75, 91.09 ± 44.52 and 114 individuals when they were fed with the first, second, third and the fourth instar larvae of the host, respectively.     

Seasonal population trend of the peach fruit fly (PFF), Bactrocera zonata (Saunders) (Diptera: Tephritidae), in Assiut,Northern Upper Egypt

The population of peach fruit fly during 2011 season increased gradually starting from the fourth week of July to reach its first major peak throughout the second week of September with 1340?flies/trap/day for traps suspended at 1?m height and during the third week of September with 909?flies/trap/day for traps hung at 2?m heights. Afterwards, the population trend showed a slight but gradual declining trend from the third week of September up to the third week of October. The population was then increased to reach its second major peak during the fourth week of October with 696 and 595?flies/trap/day for traps hung at 1 and 2?m heights, respectively. The greatest drop in the trapped population at both trap heights was observed from the second week of November until the end of the season (second week of December). A total of 105270?flies/trap at both 1 and 2?m trap heights during the entire seasons of 2011 were recorded. In 2012 season, the population followed nearly the same trend as that observed during 2011 season with minor variations. One major peak of abundance was recorded during the first week of October with 1344 and 955?flies/trap/day for traps hung at 1 and 2?m, respectively. The second major peak (1104 and 894?flies/trap/day) was observed during the fourth week of October for traps suspended at 1 and 2?m, respectively. A remarkable decrease in the population could be seen from the first week of December until the end of the season (fourth week of December). Statistical analysis of the data showed highly significant differences between fruit fly population captured at 1?m trap height (Mean = 446.9 ± 97?flies/trap/day) and that captured at 2?m trap heights (Mean = 321 ± 72?flies/trap/day) with paired t of 4.7^** and p-value of 0.0001^**.     

Bottom-up and top-down effects in a tritrophic system: the population fluctuations of Plutella xylostella and its parasitoid,Oomyzus sokolowskii on the cauliflower cultivars in field conditions

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae), has worldwide distribution and found wherever cruciferous plants is grown. In this study, fluctuations of parasitism rate of P. xylostella by Oomyzus sokolowskii on different cauliflower cultivars were evaluated in the field during 2011 at research station of the Shahed University (South of Tehran). This investigation was conducted on the eight cauliflower cultivars including Smilla, Snow mystique, White cloud, Buris, Galiblanka, Snow crown, SG and Tokita in a randomised complete block design with five replications. The results showed that density of total larva and pupa of the diamondback moth on Buris and Snow crown cultivars is lower than other cultivars. The highest and the lowest percentage of parasitism by O. sokolowskii was observed on Buris cultivar (7.93?±?0.91%) and SG cultivar (1.28?±?0.36%) during the season, respectively.     

Influence of larval rearing temperature on the quality of cold‐stored Oomyzus sokolowskii Kurdjumov (Hymenoptera: Eulophidae)

Oomyzus sokolowskii, an important parasitoid of Plutella xylostella, has great potential for use in biological control. Storage at suboptimal temperature is valuable for increasing the shelf‐life of insect parasitoids. In this study, O. sokolowskii larvae were reared at 30/25, 25/25 and 25/20°C light/dark (65 ± 5% RH, 16 : 8 h L : D) until pupation. The pupae were then cold‐stored at 4 ± 1°C (60 ± 5% RH, full darkness). The pupae were removed out from the storage at 10, 20, 30 and 40 days after storage (DAS) and maintained at 25 ± 2°C until adults emerged or pupae died. Quality of the emerging adults and their F₁ offspring were assessed. Incidence of parasitism by O. sokolowskii was higher at 30/25°C than at 25/20°C. Cold storage of O. sokolowskii pupae greatly affected the fitness of the parasitoid: adult emergence rates were lower in the 40 DAS treatment than in other treatments; when O. sokolowskii larvae developed at 25/25°C, female proportions of the emerged adults were lower in the 40 DAS treatment than in the 0 and 10 DAS treatments. Larval rearing temperature mildly affected the adult emergence rate, post‐storage developmental time and female proportion with a few exceptions. Number of parasitoids emerged per host pupa, and incidence of parasitism by the females were neither affected by larval rearing temperature nor cold storage duration. Trans‐generational effects on F₁ offspring were evident in adult emergence rate, egg‐adult developmental time and female proportion which were negatively affected by long duration of storage (40 days), but not by larval rearing temperature with a few exceptions. In conclusion, O. sokolowskii pupae could be stored at 4°C for up to 30 days without significant fitness loss.     

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.     

Thermoregulation in the primitively eusocial paper wasp, Polistes dominulus

Regulation of wing muscle temperature is important for sustaining flight in many insects, and has been well studied in honeybees. It has been much less well studied in wasps and has never been demonstrated in Polistes paper wasps. We measured thorax, head, and abdomen temperatures of inactive Polistes dominulus workers as they warmed after transfer from 8 to ~25°C ambient temperature, after removal from hibernacula, and after periods of flight in a variable temperature room. Thorax temperature (T _th) of non-flying live wasps increased more rapidly than that of dead wasps, and T _th of some live wasps reached more than 2°C above ambient temperature (T _a), indicating endothermy. Wasps removed from hibernacula had body region temperatures significantly above ambient. The T _th of flying wasps was 2.5°C above ambient at T _a = 21°C, and at or even below ambient at T _a = 40°C. At 40°C head and abdomen temperatures were both more than 2°C below T _a, indicating evaporative cooling. We conclude that P. dominulus individuals demonstrate clear, albeit limited, thermoregulatory capacity.     

Laboratory rearing of Lytopylus rufipes (Hymenoptera: Braconidae: Agathidinae), a parasitoid wasp of the oriental fruit moth,Grapholita molesta (Lepidoptera: Tortricidae), using apple and a commercially available diet

Lytopylus rufipes (Nees) (Hymenoptera: Braconidae: Agathidinae) is a potential natural enemy of the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), but there is no established method to rear this wasp continuously. In the laboratory, female wasps can produce both female and male progenies without mating (deuterotokous), but host-infested plants are necessary to trigger oviposition behavior. In this study, immature apples were used because they keep well. Grapholita molesta larvae were transferred to immature apples, and then exposed to L. rufipes females. After parasitization, these apples were transferred to blocks of artificial diet (Silkmate 2M) for further rearing. Using this transitional diet system, L. rufipes females develop in 25.1?±?1.8 (mean?±?SD) days from egg to adult, but male wasps require only 23.8?±?1.0 days. Furthermore, the longevity of female wasps was 12.2?±?7.3 (mean?±?SD) days, and the parasitism rate was 26.4 (95% Cl: 22.2–30.6). Female wasps can attack host larvae in all instars, but parasitism of first-instar larvae is more successful. Therefore, first-instar larvae of G. molesta are recommended for establishing a L. rufipes colony under laboratory conditions. This system decreases the requirement for plant material and maintains continuous production of L. rufipes.

     

Distribution,dispersal and spread of the invasive social wasp (Vespula germanica) in Argentina

We studied the distribution and spread of the invasive social wasp Vespula germanica in Argentina, focusing on the contribution of queen dispersal to territorial expansion. Vespula germanica is native to Eurasia and has invaded several regions of the world, including Southern Argentina. Flight potential of field‐collected queens was measured using flight mills. Also, by means of an extensive survey we estimated the rate of spread by analysing the relationship between years since arrival and distance from the introduction locality. The mean distance flown by wasp queens in flight mills was 404.7 ± 140.8 m (mean ± SE, n = 59), while the rate of spread of V. germanica was estimated at 37.2 ± 2.1 km year^?1 (mean ± SE, n = 67), although faster towards the south. The observed spread rate of V. germanica wasps in Argentina confirms the invasive potential shown by several Hymenoptera species worldwide. Still, a stratified geographical expansion pattern does not match observed queen dispersal abilities, suggesting that human‐aided transport of hibernating queens is the central driver of the current distribution of these wasps. We suggest that despite several life‐history traits known for social insects that contribute to successful invasion, wasp spread must still rely strongly on human mediated pathways. This observation sheds light on those factors that are crucial for managing invasions of this and related pestiferous wasps.     

Predation and functional response of the multi-coloured Asian ladybeetle Harmonia axyridis on the adult Asian citrus psyllid Diaphorina citri

Diaphorina citri (Hemiptera: Liviidae) is a vector for the citrus Huanglongbing greening disease, which can reduce crop yields. Harmonia axyridis (Coleoptera: Coccinellidae) is known to prey on D. citri nymphs; we investigated the predation capacity and functional response of H. axyridis on adult D. citri. H. axyridis larvae exhibited Holling’s type II functional response to different densities of adult D. citri. For second, third and fourth instar H. axyridis larvae, the successful attack rates were 0.75?±?0.22, 1.06?±?0.11, and 1.04?±?0.26, respectively; the handling times were 18.08?±?5.37, 0.45?±?0.07, and 0.24?±?0.07?h, respectively; and the estimated maximum predation rates were 4, 54, and 102, respectively. Fourth instar larvae had the lowest handling time. Adult H. axyridis consumed more D. citri adults maintained at 15–20°C than at 30–35°C, with an optimal temperature of 17.28°C. More adults were consumed during the day than at night, with peak consumption between 12:00 and 14:00?h, not differing significantly differ between predator genders. Adult H. axyridis reared on the aphid Acyrthosiphon pisum were tested for D. citri predation; these H. axyridis had successful attack rates, handling times, and estimated maximal predation rates of 0.66?±?0.18, 0.82?±?0.26?h, and 29, respectively. Conversely, those fed and tested on D. citri had corresponding rates of 0.99?±?0.17, 0.38?±?0.12?h, and 63, respectively. Significant H. axyridis predation on adult D. citri indicated its enhanced role in suppressing both nymph and adult D. citri.     

Laboratory studies ofTetrastichus sokolowskii

Under laboratory conditions,Tetrastichus sokolowskii Kurdj. attacksPlutella xylostella larvae of all ages. Development time took from 13 to 19 days. The number of adult parasitoids that emerged per pupa was 8.6±0.2, of which 17.3%±1.2% were ✗. Males were smaller (1.11±0.04 mm) than ♀ ♀ (1.38±0.04 mm). About 62.7±16.9 offspring could be produced per ♀ ♀ and 48% of the eggs were laid on the 1 st day. Both sexes lived longer when fed on sugar or honey solution. When fed on honey, the longevity of ✗ ✗ and ♀ ♀ were 4.8±0.7 and 11.1±1.1 respectively. Despite multiple oviposition attacks, there was no significant difference in the number of offspring produced.      

Effects of three insecticides on adult bionomics of the parasitoid Encarsia formosa

Pesticides can negatively affect many life history traits of natural enemies. In this study, we studied the effects of three insecticides with different modes of action on the bionomics of Encarsia formosa, a parasitoid of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Buprofezin (800 mg (a.i.)/L) and pyriproxyfen (50 mg (a.i.)/L) were selected among IGRs, while fenpropathrin (250 mg (a.i.)/L) was selected from the Pyrotheroids. Adults of E. formosa were treated via exposure to residues of insecticides on leaf discs. Our results revealed that buprofezin and pyriproxyfen did not affect longevity and fecundity, while fenpropathrin significantly reduced the longevity and fecundity of treated wasps. Results of logistic regression revealed that control, buprofezin- and pryproxyphen-treated E. formosa was a function of host density and followed a type II functional response. In contrast, E. formosa treated by fenpropathrin showed a type III functional response. Estimated attack rate for buprofezin and pyriproxyfen did not differ significantly from the control, whereas fenpropathrin-treated wasps showed a lower attack rate than the control. According to the obtained results, handling time of fenpropathrin-treated wasps was significantly higher (4.57 ± 0.5) than the control (2.83 ± 0.35). Our results showed that the maximum parasitism rate achieved by control wasps was 8.39, while the rate for buprofezin-, pyriproxyfen- and fenpropathrin-treated wasps was 6.99, 7.69 and 5.25, respectively. Overall, results suggest that buprofezin and pyriproxyfen can be used in an integrated pest management programme or biological control programme without destructive effects on the efficiency of this natural enemy in green houses.     

Activity patterns and egg production in Coccophagus bartletti, an aphelinid parasitoid of scale insects

ABSTRACT.

• 1 Daily patterns of oviposition and host-feeding were examined in Coccophagus bartletti Annecke & Insley. Females began to host-feed and oviposit during the second or third day after emergence. Thereafter, both activities occurred regularly.
• 2 During long observation periods (5 h) most oviposition (93%) and host-feeding (90%) occurred within the first 3.5 h of wasps first encountering hosts. Experiments demonstrated that levels of activity were low for the rest of the day, and nocturnal oviposition occurred only if wasps had no alternative.
• 3 Dissection of female wasps that had been exposed to hosts, or withheld from them, for given periods of time, revealed that activity levels are governed by egg availability. Dispersal activity may also be influenced by the physiological state of the ovaries.
• 4 Production of a full complement of eggs (at 24±1°C (12 h L) and 18±1°C (12 h D)) took 48h or longer after host-feeding, and if wasps were withheld from hosts and provided with honey, the effects of egg resorption could be detected after about 10 days. Trends in oögenesis and oösorption in C. bartletti females seem not to conform with interpretations of oögenesis-oösorption cycles in other parasitoids.
• 5 The pattern of activity exhibited by C. bartletti females is not inflexible, but the major aspects mentioned above are species-specific. In general, information is needed about daily and hourly patterns of parasitoid oviposition and host-feeding before experiments are designed to test theories of parasitoid behaviour. Interpretation may otherwise rest on assumptions about their physiological condition.

     

Sedentariness at Work: How Much Do We Really Sit?

Sedentariness is associated with obesity. We examined whether people with sedentary jobs are equally inactive during their work days and leisure days. We enrolled 21 subjects of varying weight and body fat (11 men:10 women, 38 ± 8 years, 83 ± 17 kg, BMI 28 ± 5 kg/m², 29 ± 11 fat kg, 35 ± 9% fat). All subjects continued their usual work and leisure‐time activities whilst we measured daily activity and body postures for 10 days. The data supported our hypothesis that people sit more at work compared to leisure (597 ± 122 min/day cf 484 ± 83 min/day; P < 0.0001). The mean difference was 110 ± 99 min/day. Similarly, work days were associated with less standing (341 ± 97 min/day; P = 0.002) than leisure days (417 ± 101 min/day). Although the walking bouts did not differ significantly between work and leisure (46 ± 9 vs. 42 ± 9 walking bouts/day); the mean free‐living velocity of a walk at work was 1.08 ± 0.28 mph and on leisure days was 0.94 ± 0.24 mph (P = 0.03) and the average time spent walking was 322 ± 91 min on work days and 380 ± 108 min on leisure days (P = 0.03). Estimates of the daily energetic cost of walking approximated 527 ± 220 kcal/day for work days and 586 ± 326 kcal/day for leisure days (r = 0.72, P < 0.001). Work days are associated with more sitting and less walking/standing time than leisure days. We suggest a need to develop approaches to free people from their chairs and render them more active.     

Does mass rearing of field collected Trichogramma brassicae wasps influence acceptance of European corn borer eggs?

The purpose of our study was to identify a trait that changes quickly during Trichogramma mass rearing, and that could therefore be used to monitor stock deterioration. Quality deterioration in mass reared Trichogramma wasps was evaluated by examining host acceptance behaviour of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) on the target host Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). We compared three replicate lines (designated ‘E’) reared in the laboratory on the factitious host Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) for 27 generations, a line ‘O’ reared in the laboratory on O. nubilalis for 24 generations, and a line ‘F’ reared in the laboratory on O. nubilalis for only two generations. All lines were initiated from field collections of O. nubilalis egg masses. We also evaluated natal host effects by rearing each line on E. kuehniella as well as on O. nubilalis for the last generation prior to testing. The percentage of wasps accepting the O. nubilalis egg mass was significantly higher for the E lines (69.6%) than for the F line (46.5%), while wasps of the O line showed intermediate (57.4%) acceptance. Thus, wasps laboratory reared on E. kuehniella performed better than wasps which had recently been collected in the field. Wasps of the O line showed extended probing behaviour compared to the other lines. Lines did not differ in the duration from the first host contact to the beginning of the drilling, probing or trembling behaviour. Natal host (E. kuehniella or O. nubilalis) did not affect acceptance of the target host O. nubilalis. Even though there is some evidence of adaptation to laboratory rearing conditions, we found no indication for quality deterioration in terms of acceptance behaviour of the target host O. nubilalis when T. brassicae was mass reared on the factitious host E. kuehniella.     

Flight activity of the damson–hop aphid, Phorodon humuli.

Flight activity of Phorodon humuli was monitored using suction traps, laboratory studies and mark and recapture experiments. Emigrants were trapped as they flew from a Myrobalan (Prunus cerasifera) hedge and among dwarf hops (Humulus lupulus). Daily flight curves were bimodal with 69% and 38% of emigrants caught in the morning peak near Myrobalan and among hops, respectively. The median period of flight activity was from 2 h after sunrise until 30 min before sunset. The lower temperature for flight was 13.5°C in the field and 14.9°C for take off in the laboratory. Variations in wind speed had little effect on flight activity explaining <2.5% of the total variance among insect counts. The percentage of emigrants on hop declined exponentially with time. The relationship, y= 10.9(±2.0) + 64.3(±2.3) × 0.92(±0.01)^t where t = daylight hours (standard error in parentheses), explained 98.3% of the variance. Hence, 62% of new arrivals flew within 1 day of arrival and 79% within 2 days. Similar numbers arrived as departed at 08:30, 10:30 and 12:30 h, but at 14:30 h twice as many arrived than departed and at 16:30 h, the accumulation was threefold. Daily flight curves of return migrants and males leaving hop were bimodal with 70% and 80%, respectively, trapped in the earlier peak. In the field, the median lower temperature for flight was 13.2°C for return migrants and a nonsignificantly different 12.8°C for males. The mean temperature for take off by return migrants was 15.7°C in the laboratory.     

The influence of geographic population,age, and mating status on the flight activity of the Asian gypsy moth <Emphasis Type="Italic">Lymantria dispar</Emphasis> (Lepidoptera: Erebidae) in China

The gypsy moth Lymantria dispar (Linnaeus) is a highly polyphagous herbivore that defoliates a wide variety of tree species. The influence of age and mating status on the flight activity of females was assessed in seven geographically isolated populations from China. We examined flight activity of tethered females using a computer-linked flight mill in the laboratory and found that age significantly influenced flight parameters, including total flight distance, time, and speed. Flight distance peaked in the youngest females (at 1 day of age) and declined with age. No significant differences in flight parameters were found between unmated and mated females. Females from Guizhou showed the strongest flight activity among all seven populations. The total flight distances, flight times, and maximum flight speeds at 1 day of age were 7.50 ± 2.28 km, 2.17 ± 0.51 h, and 6.18 ± 0.51 km/h, respectively. These results provide valuable information regarding the scale and speed of dispersal in hotspots and can improve the management and control of forest damage.