Life table and biological characteristics of Macrolophus pygmaeus when feeding on Myzus persicae and Trialeurodes vaporariorum

The life table and biological characteristics of the predatory bug Macrolophus pygmaeus Rambur (Hemiptera: Miridae) were studied when the bugs were fed with Myzus persicae (Sulzer) (Homoptera: Aphididae) feeding on eggplant and with Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) feeding on tomato plants. The tests were done at five temperatures between 15 and 30 °C, using a L16:D8 photoperiod and 65 ± 5% r.h. Most eggs (range 85 to 90%) hatched at 15 and 20 °C. Incubation period was shortest at 27.5 °C (8.45 and 8.38 days on eggplant and tomato, respectively). Preoviposition was also shortest at 27.5 °C (5.10 and 4.75 days on eggplant and tomato, respectively) whereas fecundity was highest at 20 °C (213.90 and 228.25 eggs on eggplant and tomato, respectively). Maximum longevity of females was at 15 °C (122.40 and 129.35 days on eggplant and tomato, respectively). Mean generation time was longest at 15 °C on both host plants (122.75 and 124.64 days, respectively). The intrinsic rate of increase of M. pygmaeus was highest at 27.5 °C with similar values on eggplant (0.0981 day^–1) and tomato (0.1040 day^–1). Doubling time was shortest at 27.5 °C (7.06 and 6.67 days on eggplant and tomato, respectively) and, also, finite rate of increase was highest at 27.5 °C (1.1031 and 1.1096 on eggplant and tomato, respectively). The results show that the predator M. pygmaeus develops well on the aphid M. persicae or on the whitefly T. vaporariorum, both of which are important pests of vegetable crops. This predator is also well adapted to the temperatures that occur both in greenhouses and in the open field in the Mediterranean region. Compared to other natural enemies of whiteflies, such as Encarsia formosa Gahan (Hymenoptera: Aphelinidae), Macrolophus pygmaeus can increase at relatively low temperatures.     

Colonization of tomato greenhouses by the predatory mirid bugs Macrolophus caliginosus and Dicyphus tamaninii

Colonization of tomato greenhouses by native predatory mirid bugs at the end of the spring cycle is common in the western Mediterranean area when no broad-spectrum insecticides are applied. Due to their polyphagy, these predators interact with pest populations and also with other natural enemies present in the crop. In this work we evaluate the abundance and timing of greenhouse colonization by these predators and their interaction with the greenhouse whitefly Trialeurodes vaporariorum, a key crop pest, and its introduced parasitoid Encarsia formosa. Although quite unpredictable, natural colonization of greenhouses by Macrolophus caliginosus and Dicyphus tamaninii, the two predominant species in our location, usually leads to the establishment of predator populations in the crop that subsequently prey on greenhouse whitefly. No preference for parasitized pupae was observed in greenhouse samples, while laboratory experiments revealed a marked tendency to avoid parasitoid pupae. In our area, IPM programs for greenhouse tomatoes and other vegetables should take advantage of the presence of this predator complex by allowing the immigration and establishment of its populations without disturbing them with highly toxic and non-selective insecticides.     

Suitability of Aphis fabae, Myzus persicae (Homoptera: Aphididae) and Aleyrodes proletella (Homoptera: Aleyrodidae) as prey for Coccinella undecimpunctata (Coleoptera: Coccinellidae)

The suitability of Aphis fabae Scopoli, Myzus persicae Sulzer and Aleyrodes proletella L. as food sources for Coccinella undecimpunctata L. was evaluated by studying the impact of prey consumption on the predator’s population growth parameters and feeding parameters. Unlike A. proletella, A. fabae and M. persicae supported the development and reproduction of C. undecimpunctata. A. fabae and M. persicae were considered to be essential prey, whereas A. proletella was considered to be an alternative prey. Aphid species showed different degrees of suitability: M. persicae significantly decreased the pre-oviposition period and increased adult longevity, fecundity and fertility compared with A. fabae. Moreover, A. fabae represents a suitable diet for larval development, but is not a suitable food source for adult reproduction. The predator’s population growth parameters, R₀, r_m and λ were increased with M. persicae, whereas T decreased. We found that the 4th instar larvae were the most voracious, particularly when fed on M. persicae; nevertheless, with this prey daily weight gain and feeding efficiency of 4th instar larvae were similar to that of individuals fed with A. fabae.     

Effect of temperature on development, growth and feeding of Coccinella septempunctata and Hippodamia convergens reared on the tobacco aphid, Myzus persicae nicotianae

Preimaginal development, mortality, aphid consumption rate, and size and weight upon reaching the adult stage of the aphidophagous coccinellids Hippodamia convergens Guérin-Méneville and Coccinella septempunctata L. collected from Karditsa, central Greece, were examined at four constant temperatures (14, 17, 20 and 23 °C) and L16:D8. The coccinellids fed on the tobacco aphid, Myzus persicae nicotianae Blackman. Egg, larval and pupal mortality was highest at 14 °C reaching 85.0, 73.8 and 29.4% in H. convergens and 49.3, 75.4 and 58.8% in C. septempunctata, respectively. Total preimaginal development ranged from 57.2 to 70.4 days at 14 °C, and to 16.9 and 22.1 days at 23 °C in H. convergens and C. septempunctata, respectively. Heavier and larger adults of H. convergens were obtained at 17 and 20 ° C. In C. septempunctata temperature did not affect adult weight while the lowest size was observed at 14 and 17 °C. Day-degrees requirements for preimaginal development in H. corvengens were 212.9 above a developmental threshold of 11.0 °C. The corresponding values for C. septempunctata were 281.5 and 10.7 °C. In H. convergens total and daily aphid consumption ranged from 46.8 aphids at 14 °C to 85.0 aphids at 23 °C and from 1.5 aphids at 14 °C to 9.2 aphids at 23 °C, respectively. The corresponding values for C. septempunctata were 112.0 and 2.7 at 14 °C and 157.7 and 12.4 at 23 °C. The results show the high potential of both predators as biological control agents against the tobacco aphid. The knowledge obtained could be essential for their appropriate use and for the improvement of mass rearing systems.     

Nymphal Development and Survival of Macrolophus pygmaeus Rambur (Hemiptera: Miridae) on Two Eggplant Varieties as Affected by Temperature and Presence/Absence of Prey

Nymphal development of the predator Macrolophus pygmaeus Rambur (Hemiptera: Miridae) was investigated on two eggplant varieties, Bonica and Black Beauty, in an attempt to identify the possible role that plant variety plays in the development and survival of the predator and to determine whether these biological characteristics are influenced by temperature and prey. The development of nymphs was studied in the presence and absence of the prey, Myzus persicae (Sulzer), at 15, 20, 25, 30, and 35°C, 65 ± 5% RH, and 16:8 h (L:D) photoperiod. Significant differences in the periods of nymphal development were evident in the two varieties at 15°C when M. persicae was offered as prey, and at 15 and 30°C, when there was no prey, significantly shorter periods of development were recorded on Bonica than on Black Beauty. Mortality rates of the nymphs were similar in the presence of prey on both varieties but, in the absence of prey, higher mortality rates were recorded on Black Beauty than on Bonica. In both presence and absence of prey, at 35°C, a small number of nymphs reached adulthood on Bonica, whereas no nymphs did so on Black Beauty. Therefore, the less suitable variety, Black Beauty, had a significant effect on the development and survival of nymphs of this predator, mainly in the absence of prey and at lower and higher temperatures. It is concluded that the selection of a suitable variety for the development and survival of M. pygmaeus, particularly in the absence of prey, could improve the efficiency of a biological control program in which this predator is going to be used. This is of particular importance for its establishment and effectiveness at the beginning of the growing season when temperature is relatively low and the prey is absent or scarce, as well as in summer when temperatures are high enough (around 30°C or even higher).     

3种寄主上桃蚜的选择性及形态分化

桃蚜是一种重要的农业害虫,寄主广泛,种下分化复杂。以采自黄土高原旱作区桃树、烟草、甘蓝上的桃蚜为研究对象,通过叶片选择法、传统比较形态测定法研究了3种寄主上桃蚜的选择性及形态分化。结果表明:在3种寄主同时存在的情况下,烟草上的桃蚜嗜食烟草,表现为63.5%的桃蚜选择烟草叶,13.8%选择甘蓝叶,8.2%选择桃叶,而甘蓝和桃树上的桃蚜对原寄主没有表现出明显的嗜好性;从形态指标来看,3种寄主上的桃蚜在体长、触角末节长度、后足腿节长度、触角与体长的比例方面存在显著差异(P0.05),说明这几个特征可以作为区分这3种寄主上桃蚜的依据。综合分析可以初步认为黄土高原旱作区烟草上的桃蚜可能形成了寄主专化型-烟草型。     

蠋蝽成虫对马铃薯甲虫卵和低龄幼虫的捕食能力

[目的] 马铃薯甲虫是我国已公布的全国农业植物检疫性有害生物名单中的害虫,自新疆传入后对我国马铃薯产业造成了巨大的损失,研究蠋蝽成虫对马铃薯甲虫卵和低龄幼虫的捕食能力,可为利用天敌防治马铃薯甲虫提供理论依据。[方法] 采用室内饲养观察研究方法,并用Holling Ⅱ型圆盘方程对研究结果进行拟合,计算寻找效应。[结果] 蠋蝽成虫能够捕食马铃薯甲虫卵和低龄幼虫,且捕食功能反应均符合Holling Ⅱ型圆盘方程,蠋蝽成虫对马铃薯甲虫卵和低龄幼虫的功能反应方程分别为N_a=0.2862N/（1+0.0198N）和N_a=0.8400N/（1+0.0709N）;在一定范围内,蠋蝽成虫对马铃薯甲虫卵和低龄幼虫捕食量在理论上随密度的增加而增加,当马铃薯甲虫的卵和低龄幼虫的密度分别达到20粒和20头时,蠋蝽成虫的捕食量最高;蠋蝽成虫对马铃薯甲虫卵和幼虫的最大日捕食量是14粒和12头,瞬时攻击率是0.2862和0.8400;蠋蝽对马铃薯甲虫卵的控制能力（4.1299）小于对低龄幼虫的控制能力（9.9526）。[结论] 蠋蝽成虫对马铃薯甲虫卵和低龄幼虫有较好的捕食能力,但控制能力不同。     

Effect of diet and mating status on ovarian development and oviposition in the polyphagous predator Macrolophus caliginosus (Heteroptera: Miridae)

The mirid bug Macrolophus caliginosus is commercially reared on eggs of Ephestia kuehniella, constituting an effective but expensive factitious food. Artificial diets can decrease the rearing costs of this natural enemy, but developing and evaluating an artificial diet is a very time-consuming activity. In the current study, development and reproduction of M. caliginosus on two artificial diets based on egg yolk were investigated. The artificial diets resulted in longer development and lower adult weights, but survival was comparable with that of control insects fed E. kuehniella eggs. Reproductive potential of the predator reared on factitious and artificial foods was assessed using a dissection method. The influence of nymphal food on fecundity was less important than that of adult food. Adults fed E. kuehniella eggs had a preoviposition period of about 4 days, whereas adults offered only plant material started laying eggs about 7 days after emergence. Ovarian scores at day 7 were higher for females fed E. kuehniella eggs than for those given access only to a tobacco leaf. Ovarian scores were not significantly affected by mating status. In a final test, a parallel comparison of two methods for assessing reproductive response to diet was made. Here, adult couples were offered one of four diets: E. kuehniella eggs, one of two artificial diets or no food. Half of the females were dissected and the other half was held for determining lifetime oviposition. Females fed E. kuehniella eggs had superior ovarian scores and laid more eggs than those fed either artificial diet or those given no extra food. A good correlation (r = 0.97) was obtained between ovarian scores and oviposition data, indicating that dissecting females after 1 week provides a reliable estimate of fecundity as affected by diet quality. Rapid reproductive assessments as used in the current study will help to increase the rate of development of artificial diets and may contribute to more cost effective production methods for augmentative biological control agents.     

Genetic variability in host plant adaptation of the green peach aphid, Myzus persicae

The green peach aphid, Myzus persicae (Sulz.), is polyphagous on over 400 plant species in more than 50 families. Phenotypic plasticity of individuals and genetic variability in the population presumably contribute to this polyphagy. The genetic variability in field populations of M. persicae was assessed with respect to their adaptation to sugar beets and potatoes. An analysis of more than 1 000 clones, sampled during 1980, 1981 and 1982 from different host plants in the field, revealed a wide genetic variability in host plant adaptation to sugar beets as well as to potatoes. Both traits seem to be inherited independently from each other and do not correlate with clone-specific host plant preference of apterous adults. The aphid M. persicae can be characterized as a polyphagous insect species with a wide, continuously distributed variability and a broad phenotypic plasticity. A general differentiation of herbivorous species into generalists and specialists tends to ignore the genetic component in the complex of insect-plant relationships.

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Zusammenfassung Die Grüne Pfirsichblattlaus Myzus persicae (Sulz.) lebt polyphag an über 400 Pflanzenarten in mehr als 50 Pflanzenfamilien. Ein breites Nahrungsspektrum einer Art ergibt sich jedoch aus der phänotypischen Plastizität des Individuums oder einer Klonlinie und der genetischen Variabilität der Population. Felpopulationen der Grünen Pfirsichblattlaus wurden auf ihre genetische Variabilität bezüglich der Wirtspflanzenanpassung an Rübe und Kartoffel untersucht. Eine Analyse von mehr als 1 000 Klonen, die über die Jahre 1980, 1981 und 1982 im Rheinland gesammelt wurden, lassen eine breite Variabilität in der Wirtspflanzenanpassung der Population erkennen. Beide Merkmale scheinen unabhängig voneinander vererbt zu werden und zeigen keine Beziehung zum Wirtswahlverhalten adult apterer Läuse der entsprechenden Klone. Die Art M. persicae kann daher charakterisiert werden als eine polyphage Insektenart mit einer breiten genetischen Variabilität und einer grossen phänotypischen Plastizität. Eine generelle Differenzierung von Herbivoren in Generalisten und Spezialisten vernachlässigt die genetische Komponente in der komplexen Beziehung zwischen Insekten un ihren Wirtspflanzen.

     

Effects of sub-lethal imidacloprid levels on potato leafroll virus transmission by Myzus persicae

The effects of sub-lethal imidacloprid concentrations on acquisition and inoculation of potato leafroll virus (PLRV) by Myzus persicae (Sulzer) (Hemiptera: Aphididae) were investigated. In experiments using two aphid clones to acquire PLRV from infected potatoes, virus transmission declined significantly with increasing concentrations of imidacloprid. The same was true in experiments using imidacloprid-treated Physalis floridana Rydb. as acquisition sources. When viruliferous M. persicae were placed on uninfected, imidacloprid-treated P. floridana, there were significant declines in PLRV transmission. Sub-lethal concentrations of imidacloprid clearly inhibited both acquisition and inoculation of PLRV by M. persicae, either through poisoning, temporary intoxication, and/or antifeedant effects.     

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

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

The brine shrimp Artemia sp. as alternative prey for rearing the predatory bug Macrolophus caliginosus

The predatory bug Macrolophus caliginosus, which is widely used in greenhouse crops, is limited in its application by its high price. An important factor in the cost is the high price of Ephestia kuehniella eggs, the prey used in their mass rearing. In order to reduce their price, alternatives to moth eggs are currently being investigated. The brine shrimp Artemia sp. is produced in large quantities in saline lakes and is fed as live food source to the larvae of a variety of marine and freshwater organisms. In this study, we tested Artemia sp. as prey for rearing M. caliginosus from two strains. We evaluated developmental and reproduction parameters of the predator when fed nauplii, enriched nauplii with a fatty acid, dry cysts and hydrated cysts, and were compared with those obtained when the predator was fed with E. kuehniella eggs. Nauplii had a significant reduction in survivorship, a delay in development of nymphs and a low reproduction of adults. Nauplii enriched with docosahexaenoic acid (DHA, 22:6n − 3), a common practice for larviculture of some marine fish species, resulted toxic to M. caliginosus nymphs and survival was quite low. On the contrary, either dry or hydrated cysts from the two strains tested of the brine shrimp produced the same nymphal survivorship, nymphal development time and weight and fecundity of adults as those obtained with E. kuehniella eggs. Demographic parameters of the eighth generation of the predator reared with cysts of the two strains, either dry or hydrated, were as good as those of moth eggs. We concluded that Artemia sp. cysts were a good substitution prey for the mass rearing of M. caliginosus.     

The effects of azadirachtin-treated diets on the feeding behaviour and fecundity of the peach-potato aphid,Myzus persicae

Adult apterousMyzus persicae, which had fed for 26 h on diet containing azadirachtin at concentrations of 25–100 ppm, produced nymphs at less than half the rate of aphids on control diets. After 50 h on azadirachtin-treated diets nymph production had virtually ceased. After this period, any nymphs produced by adults that had fed on azadirachtin-treated diets were born dead with undeveloped appendages. Honeydew production on azadirachtin-treated diets was unaffected during the first 26 h period but was approximately three times less than on control diets during the subsequent 24 h period.     

Prey Preference by the StinkbugPerillus bioculatus,a Predator of the Colorado Potato Beetle

Perillus bioculatus(F.) is sometimes considered a generalist but has most often been recorded as predator of Colorado potato beetle (CPB),Leptinotarsa decemlineata.(Say). This study was designed to analyze prey selection inP. bioculatuswith respect to factors that may lead to specialization. To establish if parental prey determines preference in na?̈ve progeny, prey selection experiments were conducted with the CPB and two unusual prey, the yellow mealwormTenebrio molitor(L.) and the house cricketAcheta domesticus(L.). Na?̈ve nymphs reared from yellow mealworm-fed parents in the absence of contact with the CPB initiated feeding more frequently on CPB (81.4%) than on cricket prey (69.6%) (P = 0.038), suggesting genetically inheritable preference for CPB. Progeny from CPBfed parents initiated feeding more frequently on CPB prey (93.3%) than on yellow mealworm prey (76.6%) (P = 0.0001), but progeny from yellow mealwormfed parents initiated feeding on yellow mealworm prey as frequently (89.2%) as on CPB (95.0%) (P = 0.613). Similarly, progeny from CPB-fed parents established proboscis contact more frequently on CPB (39.2%) than on house cricket prey (25.0%) (P = 0.008), whereas those from cricket-fed parents probed house cricket prey as frequently (12.5%) as CPB prey (15.4%) (P = 0.416). Results confirm specialization ofP. bioculatustoward CPB or related prey and suggest genetically inheritable as well as maternally reinforcible affinity toward CPB prey. However, affinity of na?̈ve nymphs for the CPB can be lowered by rearing parents on alternative prey, increasing their chances of survival when alternative prey must be relied upon.     

Biological control of Lygus lineolaris by Peristenus spp. in strawberry

Peristenus digoneutis Loan (Hymenoptera: Braconidae) was introduced to the US for biological control of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), and has since spread through much of the northeast. The purpose of this study was to determine if P. digoneutis and a native congener, Peristenus pallipes (Curtis), parasitize L. lineolaris in strawberry (where it is a key pest), and what factors relate to parasitism levels. During 1997–1999 we monitored parasitism on 17 strawberry farms in 14 counties in eastern and western New York State. We found that in eastern NY (where P. digoneutis has been established since the early 1990s), overall mean parasitism was 19.7% (ranging from 0 to 70%), mostly by P. digoneutis. Mean parasitism was significantly lower (12.3%, ranging from 0 to 58%) in western NY (where P. digoneutis was first recorded in 1999), and was mostly by P. pallipes. P. pallipes parasitism was significantly lower in eastern than western NY, suggesting the potential for competitive interaction with P. digoneutis. The insecticide regime of a farm was an important factor influencing parasitism rate, which was 5- to 6.5-fold higher on organic or casually sprayed farms than on intensely treated farms, though pest density under these three regimes was not significantly different. L. lineolaris density, and parasitism rate in nearby alfalfa and abandoned fields were also significant factors for parasitism in strawberry.     

Biocontrol of Sclerotinia lettuce drop by Coniothyrium minitans and Trichoderma hamatum

Fungal isolates, with known activity against Sclerotinia spp. in laboratory assays, were tested for their ability to control Sclerotinia minor in four field experiments (1998–2000). In the first experiment, eight fungal isolates (Trichoderma hamatum LU595, LU593, LU592, Trichoderma virens LU555 and LU556, Coniothyrium minitans LU112, Clonostachys rosea LU115 and Trichoderma rossicum LU596) were evaluated by incorporating spore suspensions into transplant potting mix and planting lettuce seedlings into a S. minor infested field site. At harvest, Trichoderma hamatum LU595, LU593, T. virens LU555 and C. minitans LU112 reduced disease by 30–50% compared with the untreated control under very high disease pressure (100%). In further field experiments C. minitans LU112 and T. hamatum LU593, applied as maizemeal–perlite soil amendments or incorporated into the potting mix, reduced S. minor disease over a range of disease pressures (29–91%). Disease control was equivalent or greater than that achieved with the standard carbendazim fungicide treatment. Both isolates were shown to effectively colonize the lettuce rhizosphere and surrounding soil and this colonization may have protected the roots from infection by S. minor. Multiple applications of C. minitans LU112 or T. hamatum LU593 formulations gave no added disease control compared with a single application at planting. Commercial formulations of both C. minitans LU112 and T. hamatum LU593 applied as transplant treatments, solid substrate soil amendments or as a spore drench gave consistent disease control and are currently being developed further.     

Macrolophus caliginosus: Functional response to whiteflies and preference and switching capacity between whiteflies and spider mites

Laboratory experiments were performed with adult female Macrolophus caliginosus Wagner (Heteroptera: Miridae) at 22ºC on bean plants to determine the functional response towards whiteflies, as well as the preference and switching capacity between the two prey species: whiteflies and spider mites. Predation of females presented with first instars of Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) was of a Type III functional response. The observed maximum predation was approximately 75 first instars at high prey densities within a 24-h period. The preference of M. caliginosus females between eggs of T. vaporariorum and Tetranychus urticaeKoch (Acarina: Tetranychidae) changed with the ratio of offered prey. The preference for T. vaporariorum eggs increased non-linearly with increasing proportions of this prey type. The average maximum predation of whitefly and spider mite eggs were approximately 166 and 111 eggs per day, respectively, at the highest ratio of the two preys. The proportion of M. caliginosus females found on the test plants at the end of the experiment increased with prey density suggesting that this mirid spends more time in areas with high prey density. Macrolophus caliginosus females are voracious predators of eggs and first instars of T. vaporariorum as well as of spider mite eggs and may thus be a valuable addition to existing methods of biological control of T. vaporariorum and T. urticae.     

Reproductive biology of the predator Macrolophus caliginosus: Effect of age on sexual maturation and mating

Macrolophus caliginosus is a polyphagous mirid bug native to the Mediterranean area where it is widely used as a biological control agent, both in protected and open-field vegetable crops. Its reproductive biology remains largely unknown and a better understanding of it will improve mass rearing and release strategies. In the present work, we studied the development of reproductive organs in females and males and how age conditioned receptiveness to mating in both sexes.Females with mature eggs in their ovarioles appear 3–4 days after adult molt with a similar pattern of ovary maturation in virgin females as in females that were kept with males of the same age. Newly molted males were found to already have active sperm in their seminal vesicles but their accessory glands did not completely develop until 3 days later. Receptivity for copulation paralleled ovarian and accessory gland maturation.     

Biology of Platycephala planifrons (Diptera: Chloropidae) and its potential effectiveness as biological control agent for invasive Phragmites australis in North America

Phragmites australis is a cosmopolitan clonal grass valued for its support of diversity-rich communities in its native range and feared for its devastating effects on native diversity where the species is introduced. Lack of successful control in North America resulted in the initiation of a biological control program. We used a combination of field surveys and common garden experiments in Europe to study life history and ecology of a chloropid fly, Platycephala planifrons, to assess its potential as a biological control agent. The fly is widely distributed (in non-flooded sites) throughout Eurasia but attack rates are generally low (mean 5–10%; max. 29%). Adults emerge in late June and may live for several months. Females lay eggs at the base of Ph. australis shoots. First instar larvae of this stem-feeding fly overwinter in dormant below-ground shoots of Ph. australis and rapidly complete development in early spring. Larval feeding destroys the growing meristem of the shoot causing premature wilting and 60–70% reductions in shoot biomass production. Early season attack and considerable impact suggest that Pl. planifrons could be a potent biocontrol agent, if it can escape suppression by natural enemies in the introduced range. However, the generally low attack rates in its native range and its dependence on dry sites appear to make the species a “second-choice” candidate for potential release in North America.