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.

     

Phenology ofHippodamia undecimnotata (Col.: Coccinellidae) in Greece

Hippodamia (Semiadalia) undecimnotata (Coleoptera: Coccinellidae), collected from central Greece and reared in cages during 1993–1994 and in vials during 1994–1995 outdoors at Kifissia, Athens, completed 5 generations per year. In both cases, adults of the 1^st, 2^nd and 3^rd generations reproduced, completing their egg laying in the same year; 4^th and 5^th generation adults reproduced both in the year they emerged and the following year. In both cases, adults of the 1^st and 2^nd generations died before winter; in 1993, adults of the 3^rd generation died before winter, in 1994, they survived until April 1995. Adults of the 4^th and 5^th generations overwintered successfully. The greatest numbers of eggs were laid by females of the 1^st and 2^nd generations. Field observations and timed counts of specimens (30 minutes per location) made on the tops of Mounts Chlomo and Kitheron and on the neighboring plain of Kopais between 1991 and 1994 revealed that most adults arrived on the mountains between late June and early September and left between the end of March and beginning of May.H. undecimnotata were not found on the plain of Kopais during the winter. Overwintered adults arrived between the end of March and beginning of May; 1^st generation adults emerged in June. The presence of a few eggs, larvae, pupae and newly-emerged adults observed on the plain during August-September 1993 suggests that at least a portion of theH. undecimnotata population in central Greece completes 2 or more overlapping generations per year.     

Etude histopathologique et cytopathologique d'une microsporidiose naturelle chez la coccinelle des cucurbitacees d'afrique,Henosepilachna elaterii [Col.: Coccinellidae]

Résumé La distribution deNosema henosepilachnae Toguebaye & Marchand, 1984 (Microsporida, Nosematidae) au cours du développement deHenosepilachna elaterii Rossi, 1794 a été étudiée en microscopie photonique et électronique. Les insectes ont été récoltés au Sénégal sur plants de melon (Colocynthis citrullus L L.), puis élevés au laboratoire. La microsporidie se développe d'abord dans le vitellus des œufs, puis dans les divers tissus des embryons. Chez les larves et les adultes, elle provoque ensuite une infestation généralisée. On trouve de nombreuses spores principalement dans le tissu adipeux, les tubes de Malpighi, les muscles, les gonades et le tissu nerveux. La transmission se fait très probablement par les voies transovarienne, orale et vénérienne. Cette microsporidiose réduit la fécondité des adultes mais ne provoque pas la mort immédiate de son h?te.

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Summary The distribution ofNosema henosepilachnae Toguebaye & Marchand, 1984 (Microsporida, Nosematidae) during development ofHenosepilachna elaterii Rossi, 1794, has been studied by light and electron microscopy. Insects were collected in Senegal, on melon (Colocynthis citrullus L.), then bred in laboratory. The microsporidia develops first in the egg vitellus, then in various tissues of the developing embryo. In larvae and adults it causes a general infection. Numerous spores were found in adipose tissue, Malpighian tubules, muscles, gonades and nervous tissue. Obviously this microsporidiosis is transovarially, venerally and perorally transmitted. It reduces adult fecundity, but does not cause immediately the death of its host.

     

Utilisation de HT18O pour mesurer la consommation alimentaire chez les larves agées deSemiadalia iinotata [Col.: Coccinellidae]

Résumé Le marquage isotopique (HT¹⁸O) des larves agées de 3^e et de 4^e stades de la coccinelle aphidiphageS. 11notata Schneider permet d'estimer la consommation alimentaire totale de chacun de ces 2 stades. Par comparaison avec une méthode d'estimation de la consommation alimentaire basée sur la pesée des proies, le marquage isotopique donne des résultats excellents chez les larves de dernier stade et elle est sans doute utilisable pour des mesures comparatives chez les larves de 3^e stade. Les avantages de cette méthode, dont le plus important est assurément son indépendance vis-à-vis de la nature de l'aliment ingéré par les larves, ses quelques inconvénients et également les différentes possibilités de son utilisation (alimentation artificielle, études sur la physiologie alimentaire, etc.) sont discutés. L'application de cette méthode à des larves L3 et L5 maintenues au laboratoire dans des conditions am biantes constantes, en présence de populations aphidiennes monospécifiques mais hétérogènes quant à leur stade de développement, nous a permis de vérifier à l'échelle individuelle que le gain de poids constitue effectivement un critère d'estimation de la consommation alimentaire totale correspondante. Dans ce cas également, les meilleurs résultats sont obtenus chez les larves du dernier stade.

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Summary The isotopic labeling (HT¹⁸O) of aged larvae (3rd and 4th instars) of the aphidophagous ladybeetleS. iinotata allows the total food consumption of both stages to be estimated. From the comparison with a method of consumption estimation based on weighing the prey, the isotopic labeling gives good results in the 4th stage larvae and is und oubtedly useful for comparative determination in 3rd stage larvae. The advantages of the method which does not depend on the kind of food ingested, the few drawbacks and the different possibilities of its use (artificial food, physiological studies) are discussed. This method was applied to 3rd and 4th stages larvae growing in the laboratory (in constant ambiant conditions) and fed with aphids of one species in different stages of development. It allowed to test, in each individual, the validity of measuring the total food consumption through the gain of weight of the larvae. Again, in this case the best results were obtained in the 4th stage larvae.

     

Trophic regulation of postdiapause ovariole maturation inCoccinella septempunctata [Col.: Coccinellidae]

In 1977 the vernal maturation ofCoccinella septempunctata L. females was investigated in relation to the variation in aphid population density on alfalfa and cereals in central Bohemia. The ovarioles do not ripen unless the aphid population density reaches a certain threshold. This leads to considerable variability in the time of vernal reproductive activity (up to 1.5 months in the same geographic locality) among subpopulations living on crops with different aphid densities. This mechanism enables the reproduction of the aphidophagous insect to synchronize with the population development of the aphid.     

Preference for medium dense grass tussocks byHippodamia convergens [Col.: Coccinellidae]

The preference in the choice of hibernacula of the convergent lady beetle,Hippodamia convergens Guérin-Meneville, was investigated with regard to morphological aspects of 2 introduced range grasses,Panicum coloratum (L.), andEragrostis curvula (Schrad.) Beetles strongly preferred tussocks with a ratio in the range of 1.0–3.0 stems per cm² for lovegrass. Preference for klein grass tussocks ranging from 110–130 stems/clump was found. No preference was shown for a particular tussock circumference. It was demonstrated that tussocks could successfully be designated as suitable for beetle aggregation.     

Laboratory rearing of the predatory coccinellidCleobora mellyi [Col.: Coccinellidae] for biological control ofParopsis charybdis [Col.: Chrysomelidae] in New Zealand

Cleobora mellyi Mulstant has been introduced into New Zealand in an attempt to controlParopsis charybdis Stål. Artificial diets and a practical method for rearing the predatory Australian ladybird,C. mellyi, are described.     

Development time ofCoccinella septempunctata in relation to constant temperatures[Col.: Coccinellidae]

Development times at constant temperatures were determined for the egg, larval and pupal stages ofCoccinella 7-punctata L., recently introduced to U.S.A. Males and females developed at the same rate. The egg stage lasted from 2.3 to 13.0 days at 30° and 15°C, respectively. Larvae feeding onAcyrthosiphon pisum (Harris), pea aphids, required from 6.2 to 31.1 days at 32.5°, and 17.0°C, respectively. These development rates are similar to those reported in the European literature.

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Résumé Les durées de développement à températures constantes ont été déterminées pour l'œuf, les stades larvaires et l'imago deCoccinella 7-punctate récemment introduit aux états-Unis. Les males et les femelles se développent au même rythme. Le stade œuf dure de 2,3 à, 13,0 j à 30° et 15°C, respectivement. L'alimentation des larves avec le puceron du poisAcyrtosiphon pisum (Harris) dure 6,2 et 31,1 j à 32,5 et 17,0°C, respectivement. Le stade nymphal est observé pendant 2,8 et 13,0 j à ces mêmes températures. Ces vitesses de développement sont les mêmes que celles données dans la littérature européenne.

     

The natural enemies of the armored scale lady-beetleChilocorus bipustulatus [Col. Coccinellidae]

The most common parasite ofC. bipustulatus larvae and pupae in Israel isH. flaminius [Hym., Encyrtidae]. A theory of the survival of hyperparasites through a mechanism which prevents overlapping of appearance was presented. The parasites, predators and pathogens which were found as well as those reviewed in the literature explain the low value ofC. bipustulatus in biological control of scale-insects in groves.

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Résumé Le parasite le plus commun des larves et des nymphes deC. bipustulatus en Israel estHomalotylus flaminius (Encyrtidae). Il a été montré expérimentalement que deux autres espèces,Achrysopophagus aegyptiacus etPachyneuron siculum, sont des hyperparasites des larves deH. flaminius. Il est présenté une théorie de la survie des hyperparasites à l'aide d'un mécanisme qui empêche les chevauchements d'apparition. Les autres hyménoptères parasites nouveaux, les fourmis les fourmilions et les champignons pathogènes ont une importance secondaire dans la réduction des populations deC. bipustulatus. Les parasites, prédateurs et pathogènes que nous avons trouvés aussi bien que ceux mentionnés dans la littérature expliquent la faible valeur deC. bipustulatus pour la lutte biologique contre les cochenilles en vergers.

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Research financed in part by grant No. FG.-Is-227, U.S.D.A.     

Ecological requirements for hibernatingPropylea quatuordecimpunctata (L.) andCoccinella septempunctata [Col.: Coccinellidae]

During 3 successive winters, we studied the dormancy sites ofPropylea quatuordecimpunctata (L.) andCoccinella septempunctata L., 2 species of ladybirds which hibernate in leaf litter. Samples of litter were taken from several kinds of forest to study the influence of 3 variables (exposure; altitude; sampling place: edge or inner wood) on the abundance of ladybirds. We found the ecological requirements of the 2 species of coccinellids to be quite different:C. septempunctata prefers forest edges orientated towards the South and the West.P. quatuordecimpunctata prefers the inner wood and does not show a preference for station exposure. For each species, the number of ladybirds collected in the samples is positively correlated with station altitude. In addition, some observations were carried out to examine the main mortality factors just before and during dormancy. In maize fields near dormancy sites, the harvest is very harmful forC. septempunctata. During the winter,P. quatuordecimpunctata andC. septempunctata suffer fromBeauveria ssp. and some ladybirds have parasitoïds.     

The observed sex ratio ofPediobius foveolatus [Hym.: Eulophidae] in field populations ofEpilachna varivestis [Col.: Coccinellidae]

Larvae ofEpilachna varivestis Mulsant, parasitized byPediobius foveolatus (Crawford), were collected in soybean fields in Maryland during 1975. AdultP. foveolatus emerging from the larvae were sexed and counted. The ratio of males to females increased as the availability of food within the host decreased. This information is useful in development of exponential models predicting hostparasite interactions.     

Superparasitism ofEpilachna varivestis [Col.: Coccinellidae] byPediobus foveolatus [Hym.: Eulophidae]: Influence of temperature and parasitoid-host ratio

Superparasitism ofEpilachna varivestis Mulsant larvae by the hymenopterous parasitoid,Pediobius foveolatus (Crawford), occurred under laboratory conditions. However,P. foveolatus avoided previously parasitized larvae in a manner which was directly related to the number of times host larvae were initially parasitized. Increasing the parasitoid-host ratio also increased percent host mortality and highest overall host mortality occurred at 15.6°C when the parasitoid-host ratio was 10∶10. Higher temperatures (22° and 28°C) and higher parasitoid-host ratios yielded higher numbers of parasitized larvae although a significant number of parasitoids failed to emerge at the highest parasitoid-host ratio. Higher temperatures along with increasing parasitoid-host ratios favored production of more male parasitoids.     

The effect of prey density on food intake by adultCheilomenes sulphurea [Col.: Coccinellidae]

The feeding rate of males of the coccinellidCheilomenes sulphurea (Ol.) was checked in 3 types of exposure arenas of 210, 476 and 2973 cm², at 3 levels of prey offered daily (40, 80, 120Aphis fabae Scopoli aphids per arena). Prey numbers affected the feeding rate much more than the size of the exposure arena.C. sulphurea males thus showed a rather high searching efficiency. The data are apparently near to the satiation threshold whereHolling's functional response curves of type II and III resemble each other.

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Résumé La consommation de proie par les males deCheilomenes sulphurea (Ol.) est étudiée dans 3 types d'enceintes dont l'espace expérimental est de 210, 476 et 2973 cm², avec 3 densités de proie offerte chaque jour: 40, 80 et 120 individus du puceronAphis fabae, Scopoli. La quantité de proies a modifié la consommation de manière plus importante que la taille de l'espace expérimental utilisé. Les males deC. sulphurea ont démontré ainsi une capacité à trouver la proie très élevée. Les niveaux de densité de proie sont évidemment près du seuil de saturation définis dans les courbes II et III de la réaction fonctionnelle deHolling.

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The experiments were performed when the 2nd author worked as a participant in a UNESCO course at the Czechoslovak Academy of Sciences, Prague.     

Response ofNabis roseipennis [Heteroptera: Nabidae] to Larvae of Mexican bean beetle,Epilachna varivestis [Col.: Coccinellidae]

Laboratory studies were done to measure predation by adult damsel bugs,Nabis roseipennis Reuter [Heteroptera: Nabidae], on 3^rd instar larvae of Mexican bean beetle (MBB),Epilachna varivestis Mulsant [Coleoptera: Coccinellidae], and to measure longevity and body weight of the nabids. In the 1^st experiment, field-collected nabids were isolated for 24h in 9 cm Petri dishes with lima bean foliage (Phaseolus lunatus L.) and were assigned to one of 3 prey treatments: either 4 3^rd-instar MBB larvae, 4 3^rd-instar larvae of boll weevil (BW),Anthonomus grandis Boheman [Coleoptera: Curculionidae], or 2 larvae of each species. No MBB larvae were attacked in either the MBB treatment or 2-species treatment. In contrast, BW larvae were attacked in both BW and 2-species treatments. Significantly more BW larvae were attacked in the BW treatment than in the 2-species treatment, and both were greater than the number of MBB larvae attacked. Nabids that did not attack prey lost weight during the 24 h, whereas those that attacked prey gained weight. In the 2^nd experiment, nabids that had attacked prey were isolated with lima foliage, and nabids that had not attacked prey were kept with MBB and lima foliage until an attack or death. In no instances were MBB attacked. Longevity and the pattern of weight loss did not differ between nabids that did or did not attack prey. We discuss possible reasons for the failure ofN. roseipennis to attack MBB larvae, as well as the implications for using nabids to influence pest populations in the field.      

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:

Introduction and evaluation ofChilocorus bipustulatus [Col.: Coccinellidae] for control ofParlatoria blanchardi [Hom.: Diaspididae] in date groves of Niger

Chilocorus bipustulatus L. was successfully established in oases of the Aïr Mountain region of Northern Niger (West Africa), where it became the major cause of mortality among adult females of the armored scaleParlatoria blanchardi Targioni-Tozzetti. This resulted in significantly lower scale infestation of date palms in a test plot when compared to a control with no introduced ladybeetles. The coccinellids were able to reproduce year-round, but during the hot season were largely confined to natural refuges composed of dense stands of date palms. Dispersal and multiplication occurred primarily during the rainy season, toward the end of which the greatest suppression of scale populations was seen.     

The biology ofHyperaspis jucunda [Col.: Coccinellidae] an exotic predator of the cassava mealybugPhenacoccus manihoti [Hom.: Pseudococcidae] in southern Nigeria

The biology ofHyperaspis jucunda (Muls.) was studied at 27°C and the incubation period averaged 5.1 days. The 1st, 2nd, 3rd and 4th larval instar averaged 2.5; 2.8; 3.4 and 5.0 days respectively. Larval development was completed in about 13.8 days while it took 7.1 days for the pupae. The total developmental time averaged 26.4 days. Mean longevity was 100 and 101 days for males and females respectively. The premating period was 19–24 h while the preoviposition period averaged 6.3 days. The generation cycle (egg to egg) averaged 32.8 days. The oviposition period was about 93 days during which an average female laid 456 eggs.     

Influence of larval rearing diet on the intensive searching behaviour ofHarmonia axyridis [Col.: Coccinellidae] Larvae

The capture of prey by last instar larvae of the aphidophagous coccinellidHarmonia axyridis Pallas (Col.,Coccinellidae) modified larval movement so that extensive search was replaced by intensive search. The continuous rearing of this species on eggs ofEphestia kühniella Zell. (Lep.,Pyralidae) or on the aphidAcyrthosiphon pisum Harris (Homopt.,Aphidae) led to conditioning. Only larvae that ate the same prey as they were reared on, adopted intensive searching movements after feeding. Using larvae reared on substitute prey in biological control systems may decrease the efficiency of the released predators.