Effects of diet on growth, fecundity and duration of tethered flight of Nezara viridula

The effects of diet during the fifth stadium on performance of adult N. viridula were determined through comparing growth, fecundity, and duration of tethered flight of insects reared on four axenic diets: fresh green bean, raw-shelled peanut, a combination of the two and soaked soybean seed. Females reared on the combination diet were heavier than those reared on green beans and oviposited more than those reared on peanuts. Three-day-old adult females reared on peanuts flew longer than those reared on green beans. More females reared on diets containing mature seed showed a capacity for extended flight and had larger fat bodies at 34-days postemergence. Thus, inadequate diet during the fifth stadium irreversibly affected growth, development, reproduction and flight capacity.

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Résumé Les effets du régime alimentaire pendant le 5ème stade sur les performances imaginales de N. viridula ont été déterminés en comparant la croissance, la fécondité, la durée du vol captif, et l'accumulation de corps gras chez des insectes élevés sur 4 régimes stérilisés. A partir de la formation des larves de 5ème stade, elles ont été alimentées sur haricots verts et arachides, ou transférées sur un régime formé exclusivement d'arachides, ou de haricots verts, ou de graines de soja trempées, cependant la durée du 5ème stade. Les insectes ont été transférés sur un régime de haricots verts et arachides à leur émergence.Les femelles élevées continuellement de haricots verts et arachides étaient plus lourdes (P<0,01) à l'émergence (161,6 mg) que celles élevées sur haricots verts (146,3 mg) pendant le 5ème stade, et pondent plus d'oeufs (P<0,08) pendant une durée de 34 jours (100,9 oeufs) que celles élevées sur arachides (54,7 oeufs). Plus de femelles élevées sur haricots verts et arachides (76,2%) pondent que celles élevées sur arachides (61,1%), soja trempé (62,5%), ou haricots verts (60,9%).Les femelles élevées sur arachides volaient plus longtemps (P < 0,01) (42,9 mn) que celles élevées sur haricots verts (19,8 mn) pendant des vols captifs le 3ème jour après l'émergence. 78% de toutes les femelles élevées sur arachides volaient >-30 mn, contre 50% pour celles élevées sur haricots verts et arachides, ou soja trempé, et 35% pour celles élevées sur haricots verts. Seulement 7% des femelles élevées sur haricots verts volaient à la 60ème minute à la fin du test, contre 25% pour les femelles soja trempé, 33% pour les femelles haricots verts et arachides, et 47% pour celles élevées sur arachides. Les femelles ont été disséquées 34 jours après l'émergence pour déterminer l'importance du corps gras. Les indices de corps gras (Kiritani, 1963) montraient que les femelles élevées sur arachides (1,8) et graines de soja (1,7) ont apparemment un corps gras plus développé que celles élevées sur haricots verts et arachides (1,5), our haricots verts (1,2), pendant le 5ème stade.Ces résultats montrent que l'alimentation pendant le dernier stade larvaire de N. viridula affecte irréversiblement la croissance, la fécondité et l'aptitude au vol des femelles. En estimant que des résultats semblables auraient été obtenus avec des insectes élevés sur ces 4 aliments depuis l'éclosion, haricots verts et arachides constituent le meilleur aliment pour l'élevage de N. viridula. Ce régime fournit une graine mûre, vraisemblablement nécessaire pour l'accumulation d'un corps gras suffisant et une aptitude au vol migratoire, et une plante verte qui fournit les aliments apparement essentiels à l'ovogenèse.

     

Short-term variations in catches of the pea moth,Cydia nigricana, in interacting pheromone traps

Short-term variations in the relative catch in each of two or three interacting pheromone traps for the pea moth,Cydia nigricana (F.), were investigated for traps aligned along the wind. The proportional catch in each trap varied widely, although the mean values accorded with previous estimates. Over consecutive short intervals during a single trapping period the proportion caught in the centre trap of a three-trap line was constant. The proportion caught in the upwind trap of two-and three-trap lines showed trends in time. These trends differed between trapping periods, but two lines of traps operated simultaneously gave similar results to each other. It is suggested that these results, which are predicted by a model based on various components of moth orientation behaviour, are caused by changes in systematic behavioural processes, not random effects. Possible mechanisms are discussed.

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Variations à court terme des captures deCydia nigricana dans des pièges à phéromones en interaction

Résumé Des données antérieures concernant les interactions entre des pièges à phéromone alignés le long du vent ont été utilisées pour déduire les caractéristiques du comportement d'orientation deC. nigricana. Ces données ont été introduites dans un modèle de simulation quantitative qui prédisait que quand les captures totales sur une ligne ont été regroupées sur une période globale de piégage, la proportion capturée dans chaque piège devrait aussi avoir des valeurs moyennes semblables, mais varie plus largement que précédemment indiqué. Les simulations concernant des intervalles consécutifs beaucoup plus courts pendant la même période de piégage ont suggéré une forme spécifique de cette variation.Cette note signale des variations à court terme dans la proportion capturée au piège qui confirment ces prédictions. Nous montrons que sur des intervalles consécutifs brefs pendant une simple période de piégage, la proportion capturée dans le piège central d'une ligne de 3 pièges est contstante, bien que sa valeur change suivant les périodes de piégage. La proportion capturée dans le piège face au vent de 2 ou 3 lignes de pièges suit cette tendance dans le temps, ce qui est généralement bien représenté avec des courbes simples. Ces tendances changent suivant les périodes de piégage, mais des lignes de pièges fonctionnant simultanément fournissaient des résultats similaires. On suggère que ces résultats sont dus à des changements dans des processus comportementaux systématiques et non à des effects aléatoires. Les mécanismes possibles sont discutés.

     

Oviposition deterring pheromone influences dispersal distance in tephritid fruit flies

We tested the hypothesis that Rhagoletis pomonella females exhibit a greater propensity for engaging in long distance (i.e.1000 m) flight following encounters with egg-infested oviposition-deterring-pheromone (ODP) marked host fruit than similar females that encounter uninfested, clean (i.e. no ODP) fruit. Female flies which were first tethered to flight mills were presented with and permitted to explore (a) ODP-marked or (b) clean fruit and then stimulated to fly. Results showed that females that had encountered a high rate of infested, ODP-marked fruit displayed long distance flight more frequently and flew greater average distances than females that had searched uninfested fruit. We discuss there results in light of contemporary foraging theory.

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Résumé La réponse d'insectes à leurs phéromones de dissuasion (ODP) est examinée généralement à un seul niveau de prospection, c'est-à-dire celui de la ressource individuelle elle-même. Ces marqueurs chimiques peuvent, cependant, fournir aussi des informations au prospecteur sur la disponibilité en ressources, tant au niveau de l'inflorescence qu'au niveau de l'habitat. Une telle information influence vraisemblablement le comportement de prospection à différents niveaux.Dans cette note, nous vérifions l'hypothèse que la rencontre avec des hôtes marqués par ODP influence la tendance de Rhagoletis pomonella (Dipt: Tephrit) à entreprendre des vols importants (c'est-à-dire interhabitats). Nous avons montré dans des expériences de laboratoire que les femelles lors de trois rencontres consécutives avec des fruits marqués par ODP: 1) entreprenaient plus fréquemment (19 cas sur 81 contre 6 sur 81) un vol à longue distance (c'est-à-dire 1000 m) et 2) parcourient des distances moyennes supérieures à celles couvertes par des femelles ayant eu la possibilité de prospecter successivement trois fruits propres (sans ODP).Nous engageons le lecteur à examiner nos résultats d'un point de vue qualitatif. Nous ne pouvons nous attendre à ce qu'un vol à longue distance se produise aussi facilement dans la nature qu'au laboratoire, étant donné le plus grand nombre de variables (par exemple, la taille de l'arbre) qui peuvent y modifier le vol réel.Pour terminer, nous discutons les coûts et bénéfices potentiels qui peuvent résulter de ce comportement.

     

Small population instability and island settlement patterns

A model of extinction probability, based on the general theory of island biogeography [MacArthur and Wilson, 1967], is proposed for humans on oceanic islands; extinction probability is determined by island carrying capacity, frequency and amplitude of fluctuations in resources determining carrying capacity, and the net costs of contact and exchange between population units. The model predicts that extinction probability will determine island settlement patterns within an island group resulting in nonsettlement of islands with low carrying capacities and settlement of all islands with high carrying capacities. Data examined from the Marshall Islands tend to support the model. The model is extended to initial atoll colonization patterns. Possible requirements for initial settlement are suggested.Deceased.     

Macro nutrient cation uptake by plants

Summary In pot experiments with barley, mustard, leek, lettuce and spinach, and in a field experiment with 30 cultivars of barley uptakes of K, Mg, Ca, Na and N were studied at varying concentrations and activities of these cations in the soil solution.The sum of macro cations (K, Mg, Ca, Na) in meq per 100 g aerial plant parts were independent of the chemical composition of the soil solution, but dependent on plant species and on the N concentration in the plant.The ratios of mean net inflows of Mg, Ca and K into plants and corresponding cation activity ratios (a_Mg/a_Ca and ) in the soil solution were linearly related and highly correlated under conditions in which growth rate and/or rate of incorporation into new tissues constituted the rate determining step of cation uptake. Consequently, mean net inflows of K, Mg and Ca were independent of ion concentration and ion activity of K, Mg or Ca in the soil solution under the conditions of constant activity ratio.The results agree with the concept that plants have a finite cation uptake capacity, and that plants are in a equilibrium-like state with the activities of K, Mg, and Ca ions in the soil solution. The results indicate that both ratios and content of exchangeable cations should be considered in our evaluation of soil test data.     

Identification of a secretomotor centre in the brain of Locusta migratoria,controlling the secretory activity of the adipokinetic hormone producing cells of the corpus cardiacum

Summary After retrograde filling of axons terminating in the glandular lobe of the corpus cardiacum (CC) of Locusta migratoria with cobalt chloride, a paired group of about 15 cobalt containing cells was demonstrated in the lateral area of the protocerebrum. The axons of these cells run via the NCC II into the glandular lobe of the CC. These small neurons have the characteristics of secretory cells; they contain secretory granules of about 1000 Å in diameter. The axon terminals in the glandular lobe, making synaptic contacts with the glandular cells, contain secretory granules of the same size. It is therefore concluded that the cell groups in the protocerebrum control the activity of the glandular cells which produce an adipokinetic hormone. Arborizations of fibers of the lateral secretomotor cells are present in the dorsal neuropile of the protocerebrum, ventral of the mushroom bodies and along the tracts of the NCC I within the brain. It is proposed that these arborizations are sites of synaptic input. It is discussed that the axons of these cells might receive additional synaptic input in the storage lobe of the CC.The localization of cell bodies, the axons of which enter the storage part of the CC is described. The course of the axon tracts of the various cell groups in the protocerebrum and their connections with the NCC I and NCC II are demonstrated.Supported by the Foundation for Fundamental Biological Research (BION) which is subsidized by the Netherlands Organization for the Advancement of Pure Research (ZWO). The electron microscopical investigations were performed at the EM-unit of the Faculty of Biology, State University of Utrecht (Director: Prof. Dr. J.C. van de Kamer)The author is greatly indebted to Dr. A.M.Th. Beenakkers and Dr. H.H. Boer for their active interest and helpful advise. Thanks are also due to Mr. H. van Kooten and his staff for making the macro- and microphotographs, to Mr. L.W. van Veenendaal for preparing the electron micrographs and final assistance in the preparation of the photo pages and to Mr. D. Smit, who made the drawings     

Evaluation of Host Suitability in Prunus for Criconemella xenoplax

Methods were developed for screening Prunus selections for host suitability to Criconemella xenoplax. The relative host suitability of selections was based upon a doubling accumulation value (β) that was defined as the number of degree-days (base 9 C) required for doubling of an increment of the initial nematode population. The β value characteristic for C. xenoplax (139 ± 8 degree-days) on suitable hosts was similar to the average β value determined for several peach rootstocks known to be suitable hosts. The β values were 144 ± 21 for Halford, 141 ± 16 for Lovell, and 138 ± 10 for Nemaguard. A higher value for β could indicate poorer host suitability or resistance of a selection to C. xenoplax. All of 369 Prunus accessions tested, including eight accessions that had survived well on a field site infested with C. xenoplax, were suitable hosts. Apparently, resistance to C. xenoplax was not a factor in survival of the accessions planted in the field. Seedlings from P. besseyi, P. pumila ''Mando'', and two interspecific hybrids, Redcoat and Sapalta IR 549-1, failed to support nematode population increase in 44-81% of tests conducted, but all selections supported population increase in some tests. These accessions may have resistance mechanisms that are active only under specific conditions.     

A unified stoichiometric model for oxidative and oxidoreductive growth of yeasts

Yeasts degrade glucose through different metabolic pathways, where the choice of the pathway is dependent on the nature of the limitation in the various substrates. When oxygen is limiting in addition to glucose, yeasts often grow according to a mixture of oxidative and reductive metabolism. Oxygen may be limiting either by supply or by inherent biological restrictions such as the respiratory bottleneck in Saccharomyces cerevisiae or by both. A unified model incorporating both supply and biological limitations is proposed for the quantitative prediction of growth rates, consumption and production rates, as well as key metabolite concentrations during mixed oxidoreductive metabolism occuring as a result of such oxygen limitations. This simple unstructured model can be applied to different yeast strains while at the same time requiring a minimum number of measured parameters. "Estimators" are utilized in order to predict the presence of supply-side or biological limitations. The values of these estimators also characterize the relative importance of oxidative to total metabolism. Results from the aerobic and oxygen-limited chemostat cultures were used to corroborate the model predictions. During these experiments, the heat released by the yeast cultures was also monitored on-line. The model correctly predicted the overall stoichiometry, steady-state concentrations, and rates including heat dissipation rates measured in the various situations of oxygen limitations. Direct continuous measurements such as heat can be used in conjunction with the unified model for on-line proces control. (c) 1992 John Wiley & Sons, Inc.     

Flight behaviour of the cabbage seedpod weevil

The influence of host odour, windspeed, position of the sun, and temperature on flight behaviour of the cabbage seedpod weevil (Ceutorhynchus assimilis Paykull) were studied. This weevil showed a positive anemotaxis (upwind flight) inside the odour plume of a host crop (Brassica napus L.). Outside the odour plume the weevil showed a pronounced phototaxis at windspeeds below 1.5 m/s. At higher windspeeds, the seedpod weevils flew downwind. The cabbage seedpod weevil flies most readily at low windspeeds (less than 0.5 m/s) and at temperatures above 22 °C.