Phenology ofCoccinella septempunctata (Col.: Coccinellidae) in central Greece

Coccinella septempunctata (Coleoptera: Coccinellidae), field collected from central Greece and reared in cages during 1990–1991 and in vials during 1994–1995 outdoors at Kifissia, Athens, developed 4 complete and a 5^th partial generations per year. In both cases, only adults of the 1st generation reproduced within the year they emerged; 2^nd, 3^rd and 4^th generation adults reproduced partly in the year they emerged and partly in the following year; 5^th generation adults did not reproduce at all in 1990, and eggs/larvae produced by 4^th generation females in 1994 died before developing into adults. Adults of the 1 st and 5th generations died before winter; those of the 2^nd, 3^rd and 4^th generations overwintered successfully. The greatest numbers of eggs were laid by females of the 1^st and 2^nd generations. Visual counts made in the open field at Kopais plain in central Greece (1990–1992) and on the summit of the adjacent Mount Kitheron (1990–1994) indicate that allC. septempunctata instars were abundant in the plain between April and June, becoming scarce from July until the end of the warm period of the year following spring. NoC. septempunctata individuals were found in the plain in winter. On the summit of the mountain,C. septempunctata adults were present all year round, singly and in aggregations, except for the month of May. The most numerous arrivals of adults were noticed on the mountain in June. Emigrations of adults from there were noticed from March until the end of April.     

Insensitivity to photoperiod after diapause inSemiadalia undecimnotata [Col. Coccinellidae]

To check the sensitivity to photoperiod inSemiadalia undecimnotata Schneider the beetles were transferred to laboratory short day (12 L: 12 D) and long day (18 L : 6 D) both during diapause (mid-November) and after diapause (in mid-May, when most females were still in their hibernation quarters and when the outdoor photoperiod was 16 hr 40 min.). After diapause, most parameters of reproductive activity (fecundity, oviposition intensity, duration of pre- and post-oviposition periods) were identical at both photoperiods, indicating thus insensitivity to photoperiod. Only the incidence and duration of ovipositional arrests were higher under short-day conditions. In the middle of diapause the sensitivity to photoperiod was still high, so that reproduction was inhibited under short day and 20°–24°C.

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Résumé Au cours de ce travail on a cherché à établir la sensibilité à la photopériode chezSemiadalia undecimnotata Schneider. Les insectes furent récoltés sur les lieux d'estivo-hibernation pendant (minovembre) et après la diapause (mi-mai) et placés au laboratoire sous une photopériode courte (12 J: 12 N) ou longue (18 J : 6 N). Après la diapause, la plupart des caractères de l'activité reproductrice (fécondité, intensité de l'oviposition, durée des périodes des pré-et post-oviposition) sont identiques sous les 2 photopériodes et montrent une insensibilité des insectes à la photopériode. Seulement les arrêts de l'oviposition sont sensiblement plus fréquents et plus allongés sous la photopériode courte. Au milieu de la diapause, la sensibilité à la photopériode est encore assez élevée et empêche la ponte sous une photopériode courte et à 20°–24°C.

     

Les aptitudes trophiques et reproductrices des femelles deSemiadalia undecimnotata [Col.: Coccinellidae]

Résumé Les femelles de la coccinelleSemiadalia undecimnotata Schneider ingèrent environ 20 mg d'aphides par jour à 22°C lorsqu'il y a surabondance de proies. Dans les premiers jours qui suivent la mue imaginale, ces prises alimentaires provoquent une augmentation sensible du poids corporel des femelles qui par la suite oscille autour d'une valeur moyenne relativement stable. La rapidité de la maturation dépend de la ration alimentaire disponible pour les femelles. L'émission des premiers œufs se produit lorsque les femelles ont ingéré de 70 à 90 mg de proies. Pendant la période de ponte, il existe une relation linéaire étroite entre la consommation alimentaire et la ponte exprimées en poids frais et sous forme cumulée. Elle pourrait permettre d'envisager le dénombrement des œufs produits par les femelles comme un moyen d'estimer partiellement leur activité trophique. Toutefois au sein de la population considérée, les aptitudes reproductrices sont très hétérogènes. Cette variabilité, qui est observée dans des conditions constantes d'élevage et qui est indépendante du poids initial des individus, pourrait être d'origine génétique: dans cette éventualité, il est peut-être possible de sélectionner les femelles en fonction de leur efficacité trophique ou de leurs capacités reproductrices.

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Summary The females of the lady bird beetleS. undecimnotata Schneider ingest an average of 20 mg of aphids per day at a temperature of 22°C and in trophic conditions that are plethoric. In the first days after emergence, this feeding induces an appreciable increase of body-weight that later remains steady. Ovarian growth is depeneent on the number of prey available to females. The release of the first eggs occurs when females have ingested about 70 to 90 mg of prey. During the reproductive stage, a narrow linear relationship links feeding consumption to egg-laying, this being expressed cumulatively in mg. This relationship allows the counting of eggs produced by females to be considered as a means of partly estimating ingestion. In the population studied, the trophic and reproductive capacities are very dissimilar. This variability observed in steady conditions of breeding is not dependent on the initial body-weight of the females and seems to have a genetic source. In this eventuality, it is perhaps possible to select the females according to their trophic efficiency or to their reproductive capacities.

     

Summer diapause and winter quiescence ofCoccinella septempunctata (Col. Coccinellidae) in central Greece

Coccinella septempunctata (Coleoptera: Coccinellidae) in Greece is a multivoltine species. In the lowlands, all instars are abundant in spring becoming scarce from July until the end of the warm period of the year; they are absent in winter. In June, mostC. septempunctata adults migrate to mountainous aestivo-hibernation sites. Measurements of the duration of pre-oviposition period in females taken monthly from the summit of Mount Kitheron in central Greece (1993–1994) and transferred to laboratory conditions of high temperature (25°C), long day (16 hrs light/24 hrs), and presence of aphids, indicated that theC. septempunctata females were in diapause during July and August. The diapause gradually terminated from late August to late October and was followed by a period of quiescence extending from November to March of the following year. During the summer diapause, arrest of ovarian development was indicated by immaturity of the ovaries in all sampled females and the complete absence of vitellogenic resorption signs. Also, adults were found with enlarged fat bodies, and the median duration of preoviposition period in females transferred to the above laboratory conditions was 90 days in early July and 82 days in early August. During the period of winter quiescence, arrest of ovarian development was characterized in most samples by immaturity of the ovaries in all females and, in some samples, by the presence of a few females with signs of vitellogenic resorption. In winter, adults were found containing fat body reserves of different levels, and the median preoviposition period of females transferred to optimal breeding conditions was 29 days in early November and 16 days in mid January.     

Oviposition strategies ofCoccinella septempunctata (Col.: Coccinellidae)

In central Japan, females ofCoccinella septempunctata brucki laid eggs preferably on the under side of metal cans, wood and other materials, and the walls of a concrete gutter in sunny grasslands with colonies of aphids, in winter and spring. These materials have a high thermal conductivity, and are warmed readily by solar radiation. The development of eggs attached to these materials was accelerated by the heart from the materials. Most eggs attached to the upper surface of such materials did not hatch because they were either desiccated by direct solar radiation or eaten by predators. The under surface of metals is heated on sunny days by solar radiation, and the eggs are protected from desiccation and cannibalism. The shortening of incubation may be an adaptation to the rapid growth of aphid populations in early spring, and may reduce the chance of cannibalism.     

Factors determining winter survival inCoccinella septempunctata (Col.: Coccinellidae)

In 1993–1995, adultCoccinella septempunctata L. were sampled at several hibernation sites in the western Czech Republic. The beetles were sexed, assorted into three body size classes and exposed in artificial hibernacula to outdoor conditions, from November to April. Average survival rate was 48.4%. Winter survival was not significantly affected by year, gender or body size. However, there were significant differences between adults from different populations (hibernation sites).     

Gut contents in field sampled adults ofCoccinella septempunctata (Col.: Coccinellidae)

During two years adultCoccinella septempunctata L. were sampled at two localities in cereals and at another location throughout the whole year in different habitats. Frequency of different food types was recorded using gut dissection. Food remains were classified into aphids, other arthropods, fungal spores, pollen, soil particles. Soil particles were relatively frequent only in early spring and pollen in late summer, whereas fungal spores were most frequent in both these periods. During ladybird reproduction in winter wheat, aphid remains were present in 76.9–91.7% of all individuals and surprisingly spores were again more frequent than remains of other arthropods. Cannibalism was rare. Food ofC. septempunctata was very uniform, because nearly always the same spores (Alternaria sp.) and other arthropods (Thysanoptera) were found. Additionally a semiquantitative analysis was performed with a simple scale of gut fullness. Only in certain cases significant positive correlation were determined between aphid density in the field and the calculated “feeding state” as well as frequency of aphid remains.     

二双斑唇瓢虫对矢尖蚧的捕食作用

研究了二双斑唇瓢虫（Chilocorus bijugus Mulsant)对矢尖蚧（Unaspis yanonensis Kuwana)的捕食作用,结果表明,瓢虫雌成虫对矢尖蚧各虫态的功能反应呈Holling II型,瓢虫对矢尖蚧的捕食效应随捕食者个体间干扰作用的增加而下降,捕食作用率（E）随着瓢虫数增加呈幂函数下降曲线,温度对瓢虫的捕食效应具有显著的影响,寻找效率（a)和处置时间（Th)与温度之间呈二次函数关系,猎物密度对瓢虫生殖力的影响呈Logistic曲线。     

Predation of Clitostethus arcuatus (Col.: Coccinellidae) on Trialeurodes vaporariorum (Hem.: Aleyrodidae)

Greenhouse whitefly, Trialeurodes vaporariorum, is a serious pest of glasshouse crops. It shows resistance to different insecticides and growers are interested in finding other useful control methods. This research was carried out to study the predation potential and biology of Clitostethus arcuatus (Rossi) as one of the most important predators of this pest. Adult C. arcuatus were reared on tobacco leaves bearing colonies of greenhouse whitefly eggs under controlled conditions (25±2°C, 65±5% RH and 16 h L:8 h D). Results showed that the average developmental time of the egg, first through fourth instar larva and pupa were 2.82±0.12, 4.47±0.14, 4.54±0.1, 6.3±0.2, 7±0.22 and 3.8±0.13 days, respectively; and longevity of female and male were 66.4±2.6 and 54.9±2.5 days, respectively. The average feeding rates of female, male and larvae (first through fourth) were 61.4±0.7, 27.6±0.9 eggs/day and 12±1.03, 30.3±2.4, 41.3±2, 68.04±2 eggs/day, respectively. The larvae consumed an average of 992.2±36 eggs during the total larval developmental period with a daily mean of 45.8±0.5. A significant difference was shown between the feeding rate of fourth instar larval stages and between sexes. Females, males and one pair of C. arcuatus (♀,♂) consumed an average of 17.2±0.4, 10.6±0.8, 23.1±0.5 nymph/day; 28.5±0.9, 20.3±0.6, 47.2±0.6 pupa/day and 8±0.3, 6.5±0.54, 13.6±0.4 adult/day, respectively. The feeding rate was significantly different among whitefly life stages. Females laid an average of 3±0.23 eggs/day.     

Antennal sensilla and sexual dimorphism of the adult ladybird beetle Semiadalia undecimnotata Schn. (Coleoptera: Coccinellidae)

The antennal receptors of the adult male and female ladybird beetle, Semiadalia undecimnotata (Coleoptera: Coccinellidae), were examined by scanning and transmission electron microscopy. Twelve types of receptors were characterized and grouped into 5 morphological classes: Böhm, trichoid, coeloconic, basiconic, and chetiform sensilla. Sensory function was determined on the basis of sensillar ultrastructure and electrophysiological response. Olfactory sensilla are confined in both sexes to the 2 terminal antennal segments. In contrast, gustatory and mechanosensitive organs are present along the entire length of the antennae. Sexual dimorphism of antennal receptors is limited to the latter 2 functional classes. The principal characteristics of this dimorphism are the following: a) males possess 540 sensilla (all types), while females possess only 500; b) males exhibit 2 types of taste receptors not present in females; c) females exhibit one type of mechanoreceptor absent in males; d) the 3 sex-specific types of sensilla, which occupy the same position in males and females, are confined to the inner side of the antennae. The possible role of male-specific sensilla in intersexual communication is discussed.     

Status and importance ofRhyzobius forestieri (Col.: Coccinellidae) on citrus at chios Island, Greece, nine years after its introduction

The originally Australian coccidophagous predatorRhyzobius forestieri (Coleoptera: Coccinellidae), imported from California into Greece in 1981, was first released on citrus at Cambos, Chios, in 1983 against soft scalesCoccus pseudomagnoliarum andSaissetia oleae (Homoptera: Coccidae). It was successfully established in two orchards there. During the following decade,R. forestieri spontaneously dispersed throughout the Cambos coastal plain. In July 1992, a survey of coccidophagous coccinellids was carried out, to follow up on the dispersal ofR. forestieri on citrus and to compare its population size with that of the main native coccidophagous coccinellids. The samplings were made in 4 selected scale-infested orchards of Cambos spaced 1–2 km apart. Of a total of 337 adults and 237 larvae of coccidophagous coccinellids found,R. forestieri comprised 84.0% and 75.1%, respectively. It was present in all 4 localities; in 2,R. forestieri adults and larvae were by far the most abundant coccidophagous coccinellids.     

Rearing larval stages of Hippodamia variegata Goeze (Col.: Coccinellidae) on artificial diet

The ladybird Hippodamia variegata Goeze is a widespread species found in many parts of the world. It is an efficient predator which feeds on a wide range of pests, specially aphids and other sap feeders. Mass rearing of this predator, in order to use in biological control programmes, entails a great deal of difficulties, among which are the aspects associated with nutrition. Applying artificial diets is of a great importance in mass rearing of biological control agents. We investigated the use of 15 artificial diets that included three separated experiments, in order to rear larval stages of this ladybird. The survival rate and developmental time were assessed on each treatment. The survival rate of the larvae on best diet was 53.30, 93.33, and 93.33% in different experiments. The developmental time in the experiment 1, 2 and 3 for the larva fed on the Aphis fabae was 15.59, 15.51 and 15.94, respectively, but when nourished by the best artificial diets, this factor was 26.59, 26.60 and 20.59, respectively. Developmental time for the larvae fed on A. fabae was significantly shorter than developmental time of larvae on artificial diets. Our results showed that artificial diets have the capacity to support the larval development to adulthood.     

Functional and numerical responses of Propylea dissecta (Col., Coccinellidae)

The functional response of a ladybeetle, Propylea dissecta, to increasing density of aphid, Aphis gossypii, was of the curvilinear shape depicting Holling's type II response with fourth instar larva being the most voracious stage when compared with adult male and female. Prey handling time by different predatory stages decreased from 65.45 to 8.72 min with increase in prey density from 25 to 800. The predator aggregation and high prey density reduces the searching efficiency of the predator. Area of discovery was highest (1.4437) when a single predator was searching at minimum aphid density (25) and lowest (0.0366) when eight predators were searching at a constant aphid density (200). Mutual interference and quest constants were 0.75 and 0.40, respectively. The reproductive numerical response, in terms of eggs laid, increased curvilinearly with prey density and female laid 70.5 ± 5.55 eggs when exposed to highest prey density (400) and 12.3 ± 0.79 eggs at lowest prey density (10). The similar shapes of both functional and reproductive responses indicate that both responses are interlinked and function simultaneously.     

Locomotor Behavior of Flightless Harmonia axyridis Pallas (Col., Coccinellidae)

To improve the efficiency of the lady beetle H. axyridis as a biological control agent against aphids, a flightless population was obtained by feeding adults with a mutagen and selecting their progeny for nonflying but otherwise morphologically normal individuals. These flightless adults attempted to fly but immediately fell. They softened their fall by opening their elytrae and wings. The inability to fly could result from change in their flying behavior compared to control adults. The flight duration was very much shorter, and the wing beat frequency and, more particularly, the amplitude of the wing beats were clearly lower. More time was spent in the other components of the flight behavior such as wing rotation, wing immobility, and wing folding. The sequence of these patterns differed slightly, due mainly to change in their frequency. The locomotor behavior was not modified by the mutation, which affected only the wing muscles. Searching behavior of mutant adults differed from that of control adults only in that they took longer to encounter and ingest aphids. Nevertheless, the larval growth and reproductive rate remained unchanged. The behavioral and biological features of these flightless adults indicate that it should be possible to use them in biological control programs.     

Locomotory behavior of flightless Harmonia axyridis Pallas (Col., Coccinellidae)

To improve the efficiency of the ladybeetle Harmonia axyridis as a biological control agent against aphids, a flightless population was produced by feeding adults with a mutagen and selecting their progeny for non-flying but otherwise morphologically normal individuals. The inability to fly could result from a change in their flying behavior compared with control adults. Flight duration was very much shorter, wing beat frequency and more particularly the amplitude of the wing beats were clearly lower. More time was spent on the other components of flight behavior such as wing rotation, wing immobility and wing folding. The sequence of these patterns differed slightly mainly due to changes in their frequency. The locomotory behavior was not modified by the mutation, which only affected the wing muscles. The searching behavior of mutant adults differed from that of control adults only in that they took longer to encounter and ingest aphids. As this difference is not important, it should be possible to use this flightless population in biological control programs.     

Functional response ofCurinus coeruleus (Col.: Coccinellidae) toHeteropsylla cubana (Hom.: Psyllidae) on artificial and natural substrates

Laboratory measurements of the functional response of adultCurinus coeruleus (Mulsant) to nymphs ofHeteropsylla cubana Crawford on filter paper and on leaves of different host plants showed a significant effect of these different substrates on nymph consumption at several different densities. Moreover, this effect may be explained by the influence of the substrate on the search rate of the predator. Host plants tested includedLeucaena leucocephala (Lam) de Witt,L. diversifolia (Schlecht.) Benth. andL. pallida Britton and Rose. Results obtained may be relevant to plant-protection research programs involving the integration of biological control with host-plant resistance.      

Prevention and artificial induction of imaginal diapause in Coccinella septempunctata L. (Col.: Coccinellidae)

Excess food, long photoperiod, and high temperature prevents diapause in Coccinella septempunctata L. after the beetles had been reared through several generations under these conditions. These is an interaction between photoperiod and temperature in induction of diapause, photoperiod being the more important factor. A long photoperiod inhibits diapause even at a low temperature. The proportion of diapausing females in later generations varies inversely with the temperature if the photoperiod is short. Which factor induces diapause in adults of the first generation is not yet known.The physiological condition of beetles artificially induced to enter diapause is apparently similar to that of beetles in diapause in the field.

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Zusammenfassung Die Aufzucht des Marienkäfers Coccinella septempunctata L. unter optimalen Laborbedingungen (Langtag, erhöhte Temperatur, Futterüberfluss) bewirkte eine stufenweise Unterdrückung der Diapause. Demzufolge konnten dann diapausefreie Generationen in lückenloser Folge herangezogen werden. Wenn es aber zu irgendeiner Abweichung von den optimalen Bedingungen kommt (z.B. vom Futterüberfluss), entwickelt sich auch in den nachfolgenden Generationen ein gewisser Anteil inaktiver Käfer.Nach einer mehr als einjährigen Zucht (etwa in der elften oder zwölften Generation) wurde eine erhöhte Mortalität beobachtet. Die Zuchten würden deshalb in jedem Frühjahr durch im Freien gesammelten Imagines erneuert.Versuche mit künstlich aufgezogenen Marienkäfern der späteren Generationen zeigten, dass bei der Diapause-Auslösung die Tageslänge eine entscheidende Rolle spielt. Diesem Befund zufolge verhindern Langtagbedingungen die Auslösung der Diapause sogar bei relativ niedrigen Temperaturen. Durch Kurztagbedingungen wird die Diapause ausgelöst, aber der Anteil der diapausierenden Weibchen steht in direkter Abhängigkeit von der Temperatur, indem dieser bei niedriger Temperatur erhöht, bei höherer Temperatur herabgesetzt ist.Auf Grund vergleichender Sektionen und insbesondere biochemischer Analysen kann man vermuten, dass die physiologischen Verhältnisse bei den künstlich diapausierenden Marienkäfern denen der natürlich überwinternden ähneln.Es fällt auf, dass im Freien bei dem überwiegenden Teile der ersten Generation die Diapause unter allen Bedingungen ausgelöst wird, die sich experimentell als optimal diapausehemmend erwiesen haben. Analoge Resultate haben wir auch in unseren Labor-Versuchen bei den ersten Generationen erhalten. Es ist bisher nicht klar, ob dieser Unterschied durch variable Sensibilität zu den Aussenbedingungen oder eher durch innere genetische Unterschiedlichkeit verursacht ist. Bei der letztgenannten Möglichkeit könnte eine Erklärung darin gesucht werden, dass man für die zentraleuropäischen Populationen von Coccinella septempunctata L. eine heterogene Zusammensetzung annimmt, die zum überwiegenden Teil von Monovoltinen und nur zu einem kleineren von Polyvoltinen gebildet wird.Es zeigt sich, dass man durch präzise experimentelle Zuchten monovoltiner Insekten des gemässigten Klimas unter eindeutig optimalen Bedingungen latente Voltinismus-Tendenzen — wie z.B. potentiellen Polyvoltinismus, obligatorischen Monovoltinismus (verschiedenartig fixiert), bzw. ein Gemisch beider Typen —, welche in der Natur durch die Uniformität des Monovoltinismus verdeckt sind, aufklären könnte.

     

Life history of the importedScymnus (Nephus) Reunioni [Col.: Coccinellidae] predator of mealybugs

The life history ofNephus reunioni, introduced from the Reunioni island has been studied. Optimum temperature for the development of the entomophagous insect is 24–25°C. In this case the population has the highest survival at preimaginal stages, life duration of adults and reproductive capacity. The rate of population growth was calculated by the formula:

Modeling the age-specific per capita growth and reproduction ofRhizobius lophanthae (Col: Coccinellidae)

A per capita model for the growth, development and reproduction of the coccinellid predatorRhizobius lophanthae (Blaisd) feeding on the oleander scale(Aspidiotus nerii Bouche (Homoptera: Diaspididae)) was developed. A thermal threshold for development of 9.4°C was found. Under conditions of unlimited food, the relationship of mass at time t + 1 to that at t (in days at 25°C) suggests an 8.7 percent growth rate per mg larvae per day at 25°C. An adult female beetle produces approximately 20 eggs per day while consuming an average of 8.5 scales/day. This is approximately 2.16 eggs per scale consumed above the maintenance level of 1.88 scales per day. More precisely, this compensation point is 0.12 mg of prey/mg of predator/day at 25°C and the egestion rate is 1 - β = 0.63     

Heterogeneity of twoBeauveria bassiana strains revealed by biochemical tests,protein profiles and bio-assays ofLeptinotarsa decemlineata (Col.: Chrysomelidae) andColeomegilla macultata lengi (Col.: Coccinellidae) larvae

Biochemical profiles on API Rapid CH^* strips and protein profiles on polyacrylamide gels in the presence of sodium dodecyl sulfate were used to distinguish two strains of the entomopathogenic fungusBeauveria bassiana (Balsamo) Vuillemin, ARSEF 2991 and ATCC 44860. Next, the toxicity of these two strains was determined at concentrations of 10², 10⁴, 10⁶ and 10⁸ blastospores/ml on larvae of the Colorado potato beetleLeptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) and of its predator, the spotted ladybird beetle,Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Both strains were highly toxic toL. decemlineata larvae. However, the two strains exhibited different levels of toxicity forC. maculata larvae: ARSEF 2991 was toxic, whereas ATCC 44860 caused little coccinellid larval mortality.

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Résumé Les profils biochimiques sur galeries API Rapid CH^* et les profils protéiques sur gels de polyacrylamide ont été utilisés pour distinguer deux souches du champignon entomopathogèneBeauveria bassiana (Balsamo) Vuillemin. La toxicité de ces deux souches a été déterminée à des concentrations de 10², 10⁴, 10⁶ et 10⁸ blastospores/ml sur des larves du doryphore,Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) et de la coccinelle maculéeColeomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Les deux souches deB. bassiana se sont avérées actives à l'égard des larves deL. decemlineata. Toutefois la souche ARSEF 2991 s'est avérée pathogène pour les larves deC. maculata, alors que la souche ATCC 44860 a provoqué une faible mortalité des larves.