Formation of long‐lasting galls by overwintered nymphs in the Japanese aphid Quadrartus yoshinomiyai (Hemiptera: Aphididae: Hormaphidinae)

This paper examines the life history of a generation of galls created by the aphid Quadrartus yoshinomiyai (Hormaphidinae: Nipponaphidini) on its primary host plant, Distylium racemosum. First‐instar fundatrix nymphs of Q. yoshinomiyai initiated galls on stems of developing shoots in early April and incipient enclosed galls were found from later the same month. The galls lasted for up to 14 months, during which they grew to maturity, opened in early or mid‐April of the following year and dried up by the end of June. First‐instar fundatrix nymphs were found on winter buds, indicating that they hatched from eggs in autumn and overwintered as nymphs. These results suggest that Q. yoshinomiyai has a three‐year life cycle.     

Effects of some insect growth regulators on natural enemies of scale insects (Hom.: Coccoidea)

We report and discuss effects of four insect growth regulators: buprofezin, fenoxycarb pyriproxyfen and chlorfluazuron, at concentrations recommended for agricultural use on six species of natural enemies of homopteran pests. Dipping in buprofezin had no appreciable effect on adult mortality, oviposition and development ofComperiella bifasciata (Howard), (Hymenoptera: Encyrtidae). When exposed to hosts treated with buprofezin, percentage mortality of adultEncyrtus infelix Embleton (Encyrtidae) was low; buprofezin had some detrimental effect on immature stages ofE. infelix when applied prior to parasitization, but not when introduced after parasitization. Buprofezin had a slight effect on the immature stages ofCryptochaetum iceryae Williston (Diptera: Cryptochaetidae), while fenoxycarb and pyriproxyfen had marked detrimental effects on parasitization and/or development of the parasitoid fly. None of the larvae ofRodolia cardinalis Mulsant (Coleoptera: Coccinellidae) developed into adults after application of buprofezin, fenoxycarb or pyriproxyfen. Buprofezin and chlorfluazuron completely prevented egg hatch ofChilocorus bipustulatus L. (Coleoptera: Coccinellidae). Buprofezin did not adversely affect egg hatch and larval development ofElatophilus hebraicus Pericart (Hemiptera: Anthocoridae); fenoxycarb or pyriproxyfen applied either before or after oviposition on pine needles caused total suppression of egg hatch.     

Second-stage integrated management of apple arthropod pests

To date, integrated pest management (IPM) of arthropods in commercial apple orchards has been comprised almost exclusively of a suite of what we term first-stage IPM practices focused upon pest monitoring. These practices predict first appearance, rate of development, and abundance of pest and beneficial arthropods, which leads to recommendation of selective properly-timed pesticides as the sole tactic of controlling pests not effectively suppressed by beneficials. Here, we evaluated in Massachusetts the effectiveness of what we term second-stage IPM practices. These involved integration of pesticidal control of early season apple arthropod pests and behavioral, cultural and biological control of mid and late season apple arthropod pests in the absence of insecticide and acaricide application after mid June. The behavioral approach consisted of ringing the perimeter of several apple orchard blocks (each ca. 1 ha) with sticky-coated red spheres baited with synthetic apple odor to intercept immigrating Rhagoletis pomonella (Walsh) flies. The cultural approach focused on removing unmanaged host trees in a ring around the orchard block perimeter to prevent entry of Cydia pomonella (L.) and Argyrotaenia velutinana (Walker) females. The biological approach emphasized buildup of natural enemies of foliar pests in an orchard environment free of insecticide and acaricide use after mid June.During the second year (1988) of second-stage IPM implementation, test blocks in which baited red spheres were placed 5 m apart on perimeter apple trees and in which all unmanaged host trees within 100 m of the block perimeter had been removed received only 0.6% combined fruit injury by the above and all other pests active after mid June. Nearby blocks treated under first-stage IPM practices received 0.4% combined injury from such pests. As revealed by unbaited within-block monitoring traps, comparatively few R. pomonella flies penetrated the ring of interception traps, despite the large numbers caught on the latter. Beneficial predators of pest mites and aphids were nearly twice as common in second-stage as first-stage IPM blocks. Total cost was essentially the same for second-stage as first-stage IPM practices. But we propose a potentially much less costly, labor-saving method as a substitute for using a sticky substance to control R. pomonella flies alighting on perimeter-tree spheres.

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Résumé A ce jour, la lutte intégrée (IPM) contre les arthropodes des vergers commerciaux de pommiers, —que nous nommons IPM de première génération —, est conçue presque exclusivement comme une suite de pratiques focalisées sur l'interception des insectes nuisibles. Ces pratiques calculent d'abord la date d'apparition, la vitesse de développement et l'abondance des phytophages et des entomophages, conduisant à l'épandage à des dates appropriées d'insecticides sélectifs, comme seule tactique de protection contre les phytophages qui ne sont pas supprimés efficacement par des entomophages.Nous avons examiné au Massachusetts l'efficacité de ce que nous avons appelé le seconde génération d'IPM. Elle implique l'intégration de la lutte chimique contre des insectes consommateurs précoces, et de la lutte comportementale, culturale et biologique contre les insectes de pleine saison et tardifs, sans traitements insecticides ou acaricides des pommiers à partir de la mi-juin.L'approche comportementale consiste à encercler plusieurs massifs de pommiers (chacun de 1 ha) avec des sphères rouges engluées d'odeur synthétique de pommier pour intercepter les vols de Rhagoletis pomonella Walsh. L'approche culturale est concentrée sur l'élimination autour du verger des pommiers non inclus dans le programme de protection pour empêcher la pénétration de femelles de Cydia pomonella L. et Argyrotaenia velutinana Walker. L'approche biologique insiste sur la mise en place après la mi-juin des entomophages des ennemis du feuillage dans un verger sans insecticide ni acaricide.Pendant la seconde année (1988) de l'application du programme, les fruits attaqués par tous les phytophages après la mi-juin n'ont été que de 0,6% pour les parcelles d'arbres témoins dans lesquels les pièges rouges avaient été placés tous les 5 mètres sur les arbres du pourtour et dont les arbres non inclus dans l'expérience, avaient été enlevés sur une bande de 100 m autour de la parcelle. Des parcelles proches, traitées avec IPM première génération, avaient un taux d'attaque de 0,4% par les mêmes espèces d'arthropodes. Par rapport aux parcelles sans sphères rouges, relativement peu de R. pomonella ont pénétré au-delà de la rangée de pièges, malgré le grand nombre de mouches capturées dans ceux-ci. Les prédateurs d'acariens et de pucerons nuisibles étaient 2 fois plus abondants dans les parcelles protégées par IPM de deuxième génération, que dans celles protégées par IPM de première génération. Les coûts totaux sont à peu près les mêmes, mais nous proposons une méthode potentiellement beaucoup moins coûteuse, demandant moins de maind'uvre, par remplacement l'utilisation de la glue sur les sphères comme protection contre la pénétration de R. pomonella dans la parcelle.

     

Climate change and the spread of vector‐borne diseases: using approximate Bayesian computation to compare invasion scenarios for the bluetongue virus vector Culicoides imicola in Italy

Bluetongue (BT) is a commonly cited example of a disease with a distribution believed to have recently expanded in response to global warming. The BT virus is transmitted to ruminants by biting midges of the genus Culicoides, and it has been hypothesized that the emergence of BT in Mediterranean Europe during the last two decades is a consequence of the recent colonization of the region by Culicoides imicola and linked to climate change. To better understand the mechanism responsible for the northward spread of BT, we tested the hypothesis of a recent colonization of Italy by C. imicola, by obtaining samples from more than 60 localities across Italy, Corsica, Southern France, and Northern Africa (the hypothesized source point for the recent invasion of C. imicola), and by genotyping them with 10 newly identified microsatellite loci. The patterns of genetic variation within and among the sampled populations were characterized and used in a rigorous approximate Bayesian computation framework to compare three competing historical hypotheses related to the arrival and establishment of C. imicola in Italy. The hypothesis of an ancient presence of the insect vector was strongly favoured by this analysis, with an associated P ≥ 99%, suggesting that causes other than the northward range expansion of C. imicola may have supported the emergence of BT in southern Europe. Overall, this study illustrates the potential of molecular genetic markers for exploring the assumed link between climate change and the spread of diseases.     

Description of the larva of Kempnyia colossica (Navás) (Plecoptera: Perlidae) with biological notes

In this paper, the larva of Kempnyia colossica (Navás 1934) is described based on material collected in Parque Estadual Intervales, São Paulo State, and biological notes are presented.     

Plant secondary substances and insects behaviour

Allelochemicals are storing in different location in plant tissues as inactive form. Number of identified compounds may now exceed 100,000. Environmental factors have an effect on allelochemicals concentration in plants. Many allelochemicals classified as toxins or deterrents for herbivorous insects. Allelochemicals play a major role in feeding or ovipositing stimulants for some specialist insects. Consumption and assimilation of herbivorous insects had affected by the type of allelochemicals in host plants. Allelochemicals have an acute or chronic toxicity on herbivorous insects. Most specialist herbivorous insects rely heavily of ingested plant allelochemicals. Plant allelochemicals may influence an insect's susceptibility to pathogens such as bacteria, fungi and nematode. Specialists herbivorous insect can be using the allelochemicals in their host plants as protection against natural enemies. Some herbivorous insects are synthesising the aggregation, attracting, alarm or mating pheromone from the allelochemicals in their host plants.     

Cryptic termites avoid predatory ants by eavesdropping on vibrational cues from their footsteps

Eavesdropping has evolved in many predator–prey relationships. Communication signals of social species may be particularly vulnerable to eavesdropping, such as pheromones produced by ants, which are predators of termites. Termites communicate mostly by way of substrate‐borne vibrations, which suggest they may be able to eavesdrop, using two possible mechanisms: ant chemicals or ant vibrations. We observed termites foraging within millimetres of ants in the field, suggesting the evolution of specialised detection behaviours. We found the termite Coptotermes acinaciformis detected their major predator, the ant Iridomyrmex purpureus, through thin wood using only vibrational cues from walking, and not chemical signals. Comparison of 16 termite and ant species found the ants‐walking signals were up to 100 times higher than those of termites. Eavesdropping on passive walking signals explains the predator detection and foraging behaviours in this ancient relationship, which may be applicable to many other predator–prey relationships.     

Patterns of macroinvertebrate colonization on fresh and senescent alder leaves in two Michigan streams

SUMMARY.

• 1 Communities of invertebrates colonizing senescent autumn and fresh summer alder leaves (Alnus rugosa) were compared. Leaf packs for each treatment were placed in two hardwater streams in the Upper Peninsula of Michigan in late summer and early autumn. One stream has a cobble-bottom and the other a sand-bottom and both receive fresh leaf inputs by beaver fellings.
• 2 Fresh leaf packs remained intact after 26 days immersion, but thereafter were processed faster than were the autumn leaf packs in both streams.
• 3 In the cobble-bottom stream taxon richness (S), numbers of individuals and biomass were higher on fresh than on autumn leaves.
• 4 Fresh leaves in the sand-bottom stream supported a more diverse (H'), richer (S) and more equitably distributed (J') insect fauna than did the autumn leaves.
• 5 We discuss the simultaneous lack of fresh leaf loss and the presence of more complex insect communities on those leaves during the first 26 days of the study. Invertebrates in both mid-latitude heterotrophic streams and in tropical lowland wet forest streams may rely on fresh leaf inputs, which have received little attention.

     

Satiation of predispersal seed predators: the importance of considering both plant and seed levels

Plants can reduce the fitness costs of granivory by satiating seed predators. The most common satiation mechanism is the production of large crops, which ensures that a proportion of the seeds survive predation. Nevertheless, satiation of small granivores at the seed level may also exist. Larger seeds would satiate more efficiently, enhancing the probability of seed survival after having been attacked. However, a larger seed size could compromise the efficiency of satiation by means of large crops if there were a negative relationship between seed size and the number of seeds produced by an individual plant. We analyze both types of satiation in the interaction between the holm oak Quercus ilex and the chestnut weevil Curculio elephas. Both crop size and acorn size differed strongly in a sample of 32 trees. Larger crop sizes satiated weevils, and higher proportions of the seeds were not attacked as crop size increased. Larger seeds also satiated weevil larvae, as a larger acorn size increased the likelihood of embryo survival. Seedling size was strongly related to acorn size and was reduced by weevil attack, but seedlings coming from large weeviled acorns were still larger. The number and the size of the acorns produced by individual trees were negatively related. Larger proportions of the crop were infested in oaks producing less numerous crops of larger acorns. However, contrary to expectations, these trees did not satiate more effectively at the seed level either. Effective satiation by larger acorns was precluded by larger multi-infestation rates associated to smaller seed crops, in such a way that the proportion of attacked seeds that survived did not vary among trees with different acorn sizes. These results highlight the need of considering satiation by means of large crops and large seeds in studies of predispersal seed predation. Long-term monitoring on individual oaks will help to assess whether there is a trade-off between the number and the size of the acorns and, if it existed, how it could condition the fitness consequences of both types of satiation.     

Small Gap Creation in Belizean Mangrove Forests by a Wood–Boring Insect1

We investigated the role of wood-boring insects in the creation of light gaps within mangrove forests. We compared the frequency of gaps caused by wood borers to other gap-forming processes and characterized the physical attributes of light gaps in mangrove forests on small islands in Belize. Methods of quantifying light gaps included aerial photography, ground surveys, and experimental plots. Small light gaps (≤12 m²) were very common in Rhizophom mangle fringe, comprising almost 22 percent of these forests. Rhizophora mangle gaps were smaller than gaps in Avicennia germinans forests. In R. mangle forests, gaps were caused by branch death, and in A. germinans forests, gaps were caused primarily by downed trees. More than 91 percent of the gap-forming branches and boles in the R. mangle fringe were killed by a wood-boring cerambycid beetle, Elaphidion mimeticum, indicating that it is the major cause of small-scale disturbances in these forests. No trees or branches in the A. germinans forest were attacked by this beetle. In R. mangle forests, small gaps had significantly higher light levels and soil temperatures than areas under the closed canopy; however, soil conditions for sulfide concentrations, porewater salinity, and redox potentials were similar in small gaps and under the closed canopy. Survival of R. mangle, A. germinans, and Laguncularia racemosa seedlings was also higher inside these small gaps, indicating their importance in regeneration of mangrove forests. Feeding by wood borers is thus an important type of indirect herbivory in mangrove forests, with a critical role in ecological processes such as gap dynamics.