The roles of temperature and food quality in affecting the performance of the alder aphid, Pterocallis alni

Six successive summer generations of the alder aphid (Pterocallis alni (DeGeer) (Homoptera: Callaphididae)) were reared simultaneously in the field and under controlled temperature conditions in the laboratory. The growth and reproduction of each generation were recorded. The available food quality for the aphids was measured by weekly analysis of foliar soluble nitrogen concentrations. Although there was a significant change in leaf soluble nitrogen during the season, the decline was only 23% and this did not appear to have an adverse effect on the performance of this aphid. Instead, the major environmental factor affecting the aphid is temperature. This is evidenced by the facts that when aphids were reared at constant temperatures, there were no differences in generation performance, even though food quality varied seasonally. In addition, all generations of the aphid posess the same number of ovarioles, indicating that there is no pre-programmed anticipation of a seasonal deterioration in food quality in this aphid species.

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Résumé P. alni DeGeer (Homopt. Callaphididae) vit sur Alnus glutinosa Gaertner pendant toute l'année. L'aulne étant un arbre fixant l'azote, cette étude a été entreprise pour examiner la croissance et la reproduction de ce puceron sur cet arbre afin d'expliquer les changements de la dynamique de sa population. 6 générations successives estivales ont été élevées dans la nature et en température constante au laboratoire. La qualité de l'aliment a été mesurée chaque semaine par une microkjeldahl analyse des concentrations foliaires en azote soluble. La qualité de l'aliment varie saisonnière, mais ne diminue que de 23%; elle semble n'avoir que peu d'effets sur le puceron, puisque la fécondité dans la nature n'est réduite que pendant une génération. Quand la température est maintenue constante, il n'y a pas de différences entre les performances des différentes générations de pucerons. Ainsi, les changements saisonniers dans la croissance et la reproduction des pucerons sont provoqués par la température et non par la qualité de l'aliment.

     

Nonglandular leaf trichomes as short-term inducible defense of the grey alder,Alnus incana (L.), against the chrysomelid beetle,Agelastica alni L.

Summary The grey alder compensates leaf area losses due to insect grazing by continuously producing new leaves throughout the vegetative period. Different degrees of defoliation were attained experimentally by a controlled release of the oligophagous beetle Agelastica alni on arbitrarily selected trees from a homogenous population of young alders. The reduction in leaf area per tree significantly influenced the density of leaf trichomes, assessed 10–30 days later, on newly sprouting leaves only. Cross-correlations between leaf area reduction and trichome density were strongest for leaves which completed unfolding 14–21 days after damage. Dualchoice assays suggested a negative influence of trichomes on oviposition rate of A. alni. Removal of trichomes by shaving demonstrated the highly significant effect of trichomes on feeding behavior of adults and larvae in dual-choice assays. The role of the induced increase in trichome density as a possible short-term defense reaction against herbivorous insects is discussed.     

Diapause termination and egg hatch in the bird cherry aphid, Rhopalosiphum padi

Conclusion TastePROBE is a convenient and flexible electronic circuit designed to record action potentials from taste sensilla of insects. It facilitates the recording of slow potentials arising in taste sensilla, improves the signal to noise ratio, and preserves spike shapes. This new amplifier design combines excellent signal to noise ratio with complete compatibility as regards existing electrophysiological equipment.DC recordings have higher information content than filtered recordings. With DC recordings, spike shapes are not modified and thus better sorting is possible. Moreover, slow variations in the transepithelial potential (i.e. less than 10 Hz) are preserved. Both aspects are of considerable importance when studying the physiology of taste receptors.     

Egg production by the coccinellid Hippodamia convergens fed on two morphs of the green peach aphid, Myzus persicae

Adults of the lady beetle Hippodamia convergens Guérin-Méneville requiring aphids for egg production, were fed suboptimal amounts of apteriform virginoparous larvae or alatiform gynoparous larvae of the green peach aphid, Myzus persicae (Sulz.), and artificial diet ad lib. The beetles initiated oviposition sooner and deposited significantly more eggs when supplied with the same weight of apterous virginoparous morph. The possible nutritional, hormonal, and ecological implications of the findings are discussed.

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Zusammenfassung Die Eiproduktion des Marienkäfers Hippodamia convergens, welcher hierzu Blattläuse als Nahrung benötigt, wurde bei Fütterung mit zwei verschiedenen Morphen der Blattlaus Myzus persicae untersucht. Der Verzehr derselben Menge flügelloser Virginoparen führte im Vergleich zu geflügelten Gynoparen zu früherer und signifikant erhöhter Eiabgabe. Der hormonale und ernährungsphysiologische Hintergrund und die ökologische Bedeutung dieser Ergebnisse werden diskutiert.

     

Genetic diversity and phylogenetic relationships in alder,Alnus firma, revealed by AFLP

Molecular markers for alder,Alnus firma Sieb. et Zucc, have not been studied extensively. Here, we used amplified fragment length polymorphism (AFLP) to investigate genetic relationships among 15 natural populations. EcoRI-ACG + Msel-CTG combinations revealed the highest polymorphism (62.2%). A total of 171 DNA fragments were identified. On average, 58.1% of the AFLP markers that were generated using four primer pairs were polymorphic. Diversity was insignificant among the populations. The combination of a wind-pollinated, outcrossing breeding system along with large population sizes, and the ability to regenerate by stump sprouting may explain the high level of genetic diversity within this species. The majority (98%) of the genetic variance resided within populations. The average number of individuals that were exchanged between populations per generation was very high (N _em = 12.3). Gene dispersal in alder is apparently by seed dispersalvia water and human activity as well as through pollen. Five individuals per population were claded in the same cluster.     

First report of Mycopappus alni in Japan: species identification of the pathogenic fungus of a frosty mildew disease in Crataegus chlorosarca

A leaf disease similar to frosty mildew disease caused by Mycopappus species was detected on the leaves of Crataegus chlorosarca in Tomakomai, Hokkaido Prefecture. From morphological observations and gene analyses of rDNA-ITS, the fungus was identified as M. alni, which causes leaf blight disease on Alnus spp., Betula spp., and a Pyrus sp. in North America and Turkey. This is the first report of M. alni in Japan and Crataegus as its new host genus.     

Insecticidal effects of some biological agents on Agelastica alni (Coleoptera: Chrysomelidae)

The alder leaf beetle (Agelastica alni L., Coleoptera: Chrysomelidae) causes approximately 10% of total economic damage to hazelnut product per year in Turkey. A. alni larvae are susceptible to several pathogens indigenous to the area in which these insects occur in Turkey. In the present study, in order to find a more effective and safer biological control agent against this common pest, we evaluated the various biological agents’ insecticidal activity during the four hazelnut seasons from 2002 to 2005 on the larvae of the alder leaf beetle collected from the vicinity of Trabzon, Turkey. The tested agents are 25 insect-originating bacteria, 2 bacterial toxins and 1 viral preparation. The results showed that the highest insecticidal activity was obtained by bacterial isolates at 1.8 × 10⁹ bacteria/mL dose, within ten days on the larvae of A. alni. These are 90% for Bacillus thuringiensis biovar tenebrionis (4AA1), Bacillus sphaericus (Ar4, isolated from Anoplus roboris L., Col.: Curculionidae), and Bacillus thuringiensis (Mm2, isolated from Melolontha melolontha L., Col.: Scarabaeidae). Our results indicate that these isolates may be valuable as biological control agent.     

Lifetime egg production and egg mortality in the damselflyPyrrhosoma nymphula (Sulzer) (Zygoptera: Coenagrionidae)

Artificial oviposition sites were used to estimate egg deposition rates in the field. Females laid an average of 10.76 eggs/minute with a mean duration of 22.81 minutes, giving an average clutch size of 245 eggs. Since one mating corresponded to one clutch of eggs, lifetime mating success was used as a measure of the number of clutches produced. Mean lifetime clutch production was 5.91 clutches per female, equating to 1447 eggs per female per lifetime. Eggs were hatched in the laboratory at temperatures comparable with those in the field. Hatching was highly synchronised and the overall hatching success was 75.1%. Causes of egg mortality in the laboratory were limited to infertility and unhatchability. Since no other sources of egg mortality could be found at the study site, this value was a good reflection of hatching success in the field. Lifetime egg production and hatching success were used to estimate the number of viable offspring produced per female, giving a higher order estimate of reproductive success than has previously been published for a zygopteran.     

Juvenile hormone effects on polymorphism in the pea aphid, Acyrthosiphon pisum

When reared in short days (LD 12:12) at 15°C, apterous Acyrthosiphon pisum gave birth to sexual females (oviparae) exclusively for the first eight days of larviposition. After this time they switched to the production of parthenogenetic females (viviparae). Topical application of juvenile hormones I, II and III to fourth instar or adult ovipara-producers induced the precocious appearance of parthenogenetic females in the progeny sequence. Various forms intermediate between oviparae and viviparae were also produced and repetitive JH-I treatments resulted in a few alatiform progeny. However, many of the JH induced apterous, parthenogenetic females appeared to be normal viviparae and were capble of reproduction. Thus, prenatal treatment of oviparous embryos with JH diverts development towards the viviparous form. JH-I treatment of long-day reared A. pisum had no effect on the type of progeny produced.

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Effets de l'hormone juvénile sur le polymorphisme d'Acythosiphon pisum

Résumé Quand il est élevé sous jours courts (LN 12/12) à 15°C, le type anglais vert d'Acyrthosiphon pisum ne donne naissance qu'à des femelles sexuées (ovipares) pendant la première partie de sa période de reproduction. Ensuite quelques types intermédiaires ovipares/vivipares peuvent apparaitre avant que les pucerons ne bifurquent spontanément vers la production de femelles parthénogénétiques (vivipares). L'application cutanée d'hormones juvéniles (JH I, II, et III) aux larves de quatrième stade ou à des adultes producteurs d'ovipares provoque l'apparition prématurée d'intermédiaires et de vivipares dans la descendance. Les différentes formes intermédiaires produites par des applications répétées de J.H. comprenaient des types ailés ou partiellement ailés. Cependant, les vivipares aptères induits par J.H. étaient morphologiquement normaux et beaucoup étaient capables de se reproduire. Des traitements semblables aux J.H. de vivipares élevées en jours longs (LN 16/8) n'ont pas eu d'effets sur le type de la descendance.On ne sait pas si l'action de JH exogène sur l'induction des vivipares est direct ou indirect. La reprogrammation des embryons, autrement destinés à se développer comme ovipares, est examinée en relation avec notre connaissance du contrôle endocrine du polymorphisme des pucerons.

     

Head-plug defense in a gall aphid

The aphid Astegopteryx sp. forms a banana-bunch shaped gall consisting of several subgalls on Styrax benzoides in northern Thailand, and completes its life cycle on the tree, without migrating to secondary hostplants. We found that its soldiers had sclerotic, protruded heads with many spine-like setae, and that several soldiers cooperate to plug the ostiole of the subgall with these heads. Of 173 ostioles examined in the field, 90.8 % were plugged with no space among the guarding soldiers. Many eggs and sexuals were found within subgalls guarded by soldiers, and a number of males were found trying to intrude into these subgalls. However, they were blocked by guarding soldiers, and it was no easy task for them to intrude into subgalls. The same was true for some soldiers that had rushed out of the subgall. Guarding soldiers often prevented outside soldiers from coming back into the subgall. These findings suggest an interesting possibility that guarding soldiers might consequently select still active, reusable soldiers and strong males for sexual females in their subgall. Received 6 March 2005; revised 5 and 20 July 2005; accepted 27 July 2005.     

Foraging behaviour and resource utilization of the aphid parasitoid Pauesia unilachni: adaptation to host distribution and mortality risks

Pauesia unilachni is a parasitoid of the grey pine aphid, Schizolachnus pineti which feeds on needles of Scots pine. P. unilachni females displayed a dual movement system when foraging within a pine. They left a colony usually by foot and searched nearby needles intensively, thereby ensuring a maximum probability to encounter neighbouring S. pineti colonies. If search by foot was not successful, parasitoids changed their behaviour and searched needles by flight to cover larger distances. This behaviour was consistent both on uninfested and S. pineti-infested trees in the laboratory and in the field. In total, females allocated a 15-fold amount of time into search by foot compared to search by flight, although the overall foraging success, i.e. the number of discovered host colonies, did not differ significantly between the two movement types. However, the reduction of searching time by flight involved also higher travel mortality risks. In the field, P. unilachni got frequently entangled in spider nets when searching by flight and were killed.     

Egg distribution patterns in the almond seed wasp,Eurytoma amygdali

The egg distribution patterns ofEurytoma amygdali Enderlein (Hymenoptera, Eurytomidae), which oviposits singly in green, developing almonds, were studied in the laboratory and in the field. In the laboratory, individual females were caged with a number of almonds and the eggs deposited in each fruit were counted. In the field, eggs were censused in almonds of different varieties at regular intervals, over four seasons (1988–91). In the susceptible ‘Retsou’ variety, eggs were uniformly distributed among fruits, both in the laboratory and in the field, as long as the mean number of eggs per almond was ≤2.5. When the mean number of eggs per almond was higher the egg distributions were random. This suggests that, up to a certain level of infestation, females were able to assess egg load of fruits and oviposit in the less infested ones. The main factor enabling the females to discriminate and select the less infested almonds for oviposition is probably a host-marking pheromone. In 1990, the same patterns of egg distribution were observed in samples taken from 5 other almond varieties that are not as susceptible as Retsou and have thicker pericarp and harder endocarp. In 1991 however, when fruits developed more rapidly than in 1990, egg distributions in 3 of these 5 varieties (Truoito, Ai, and Marcona) were not uniform. Although the mean number of eggs per fruit was low (1.2–2.0), many fruits of these varieties contained no eggs. This suggests that, in some less susceptible varieties, egg distribution might also be affected by certain fruit parameters, unfavourable for oviposition, related to the pericarp thickness and endocarp hardness.     

Temporal variation in abundance of the egg predator Carcinonemertes epialti (Nemertea) and its effect on egg mortality of its host,the shore crab,Hemigrapsus oregonensis

An outbreak of the nemertean, Carcinonemertes epialti, was observed on Hemigrapsus oregonensis during October, 1982 at Campbell Cove, Bodega Harbor, California. Mean worm intensity (296 worms/crab) was the highest recorded for this nemertean egg predator on H. oregonensis. During the outbreak, male crabs were found to harbor more worms than both non-ovigerous and ovigerous females. Crab egg mortality was substantial; 83% of the ovigerous females experienced 75–100% brood mortality. The seasonal peak in worm abundance coincided with the seasonal low in crab reproduction at this locality. A method for estimating the impact of C. epialti on H. oregonensis natality was developed using crab size and fecundity, and worm prevalence and intensity. For a non-outbreak sampling period, a mean of 5.6% egg mortality was experienced by infested crabs for the period selected. Thus, brood mortality during the outbreak was much greater than that experienced at non-outbreak periods. Heavy fishing pressure on some commercially important crab species has been suggested as a possible factor inducing worm outbreaks and facilitating their continued persistence. These observations suggest that fisheries are not necessarily responsible for the outbreaks of nemerteans on commercially important crab species. However, fishing pressure may still be a sufficient condition to promote nemertean outbreaks.     

Estimating cladoceran birth rate: use of the egg age distribution to estimate mortality of ovigerous females and eggs

The birth rate of natural cladoceran populations can change rapidly (during 2–3 days), reflecting rapid changes in their environment. If the egg ratio is calculated on the basis of egg age distribution, the birth rate can be estimated at short sampling intervals (shorter than egg stage duration) by modified Paloheimo's (1974) formula. When female size structure and age of eggs in clutches at the beginning and the end of a sampling interval are known, death rates of ovigerous females and eggs in separate size classes can be determined and incorporated in birth rate estimates. All these methods have been employed using the data on the population of Diaphanosoma brahyurum from the lake Obsterno (North-Western Belarus) in July–August, 1992. The birth rate values computed by the proposed methods and Poloheimo's formula differed significantly in many cases. The accuracy of birth rate estimations from various calculation methods was tested using a computer simulation. The model contains the essential features of cladoceran life history: distinct egg, juvenile and adult stages, development of eggs and reproduction. The population was divided into 25 age classes, each of 1 day duration. Durations of the egg, juvenile and adult stages were set at 3, 6 and 20 days, respectively. The embryogenesis was divided into three egg stages, each of 1 day duration. Survivorship was set from 0.2 up to 1.0 for each age class. The survivorship and brood size were changed through each of five time intervals (days) that allowed to simulate an increase or reduction of population density. Fecundity, survivorship and egg stage duration remained constant during each of 5 days that assumed stability of an environment (this does not occur in nature). Nevertheless, the egg ratio, proportion of juveniles and birth rates were variable even under these circumstances. Computer simulations showed that Poloheimo's formula evaluates birth rate with the relative error of 62% and usually overestimates its values. We propose methods to decrease errors of birth rate estimations by 3.5–5.5 times.     

A new species ofAphidius [Hymenoptera] attacking the pea aphid,Acyrthosiphon pisum

Aphidius staryi Chen & Luhman n. sp. is described. The species was collected and introduced into California from Israel and Turkey byD. González. The new species is morphologically most similar toAphidius smithi, and keys toEady's urticae group.     

Seasonal and age-related differential mortality by sex in the Mantled Howler monkey,Alouatta palliata

Age-specific, differential mortality occurs between male and female mantled howler monkeys, Alouatta palliata,on Barro Colorado Island, Panama. A peak in mortality between 5 and 7 years is seen in males but not infernales. Dates when howler cadavers have been found suggest a seasonal mortality, with peaks in July and perhaps also in December through January.     

Methods of hatching the eggs and rearing the fundatrices of the English grain aphid, Sitobion avenae

Several methods for hatching the eggs and rearing individuals of the first generation (fundatrices) of Sitobion avenae were investigated. The most successful methods were incubation of the eggs on grass seedlings at 2°C and rearing the fundatrices on grass seedlings (overall survival 66%) and incubation of the eggs in plastic boxes at 2°C and rearing the fundatrices on wheat seedlings (overall survival 62%).

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Résumé L'éclosion des oeufs de S. avenae peut être induite par le transfert à 10°C ou 12°C, après une incubation de 75–120 jours à 2°C. Le pourcentage le plus élevé d'éclosions a été obtenu quand les oeufs avaient incubé pendant 100 à 110 jours à 2°C (67% at 71.5% respectivement) dans des petites boîtes de plastique, ou pendant 100 jours à 2°C sur des pousses de graminées (73.5%). Si les oeufs sont pondus sur blé, la plante ne peut pas tolérer la période d'incubation, mais cet obstacle peut être surmonté en obligeant les ovipares à pondre leurs oeufs sur de pousses de graminées, comme Poa annua, hôte convenable pour les fondatrices. Les ovipares peuvent aussi pondre sans difficultés sur autre chose que des végétaux, et des récipients peuvent ètre mis à incuber sans contenir du matériel végétal.

     

Lysiphlebus testaceipes,an introduced aphid parasitoid in portugal [Hym.: Aphidiidae]

Lysiphlebus testaceipes (Cresson), an exotic parasitoid species introduced in 1973–74 into southern France and subsequently widespread over the whole mediterranean France, Italy and Spain has become established even in Portugal since 1985. It was found on the southern coast of Portugal parasitizingAphis nerii Boyer de Fonscolombe. In 1986 it spread towards the North, its host range expanded and now includesAphis chloris Koch,Aphis citricola van der Goot,Aphis fabae Scopoli,Aphis frangulae Kaltenbach,Aphis gossypii Glover,A. nerii, Aphis parietariae Theobald,Aphis sedi Kaltenbach,Toxoptera aurantii (Boyer de Fonscolombe). The proved complete development and a high parasitization ofL. testaceipes onA. citricola is the 1st case in the whole Mediterranean, from where only incomplete development and a negligible percentage of parasitization (Italy) have been reported. Both the host range composition and development ofL. testaceipes indicate an increase of genetic polymorphism in the established populations. Interspecific relations ofL. testaceipes and the indigenous parasitoid species indicate an increasing dominance of the exotic biocontrol agent.      

Egg care by termite soldiers

The handling and transportation of eggs by soldiers of Prorhinotermes simplex after a nest disturbance is described. The soldiers, apart from performing alarm and defensive activities, tried to handle the eggs on the open surface. They often succeeded in lifting an egg or even a group of eggs, and then searched for a nest entrance. They either entered the nest to come out without the egg(s) within a while, or they passed the egg(s) onto a pseudergate waiting in the opening. As a result, all eggs were rapidly evacuated. Laboratory experimentation showed that pseudergates and nymphs try to deposit the eggs in a dark shelter, whereas the soldiers tend to transfer the eggs to nestmates and drop them after a while if no other termite accepts them. Received 25 February 2005; revised 26 April 2005; accepted 3 May 2005.