Observations on the seasonal abundance ofIcerya purchasi onAcacia baileyana in Adelaide,South Australia

Population estimates of the cottony-cushion scale,Icerya purchasi Maskell were obtained from 2Acacia baileyana F. von Mueller trees in Adelaide, South Australia. Most scales were located within 50 cm of the tip of the twig (sample unit), some adults being found on thick woody branches (5 to 10 cm Ø) and on the tree trunk (>50 cm Ø). Scales were present throughout the year, mostly in very low numbers, and completed 2 annual generations i.e. from April to October and from November to April. This was confirmed by data on the duration of development from a field experiment with 12 sets of monthly cohorts.     

Feeding range studies of Rodolia cardinalis (Mulsant), a candidate biological control agent of Icerya purchasi Maskell in the Galápagos islands

The immediate threat of the cottony cushion scale, Icerya purchasi Maskell (Homoptera: Margarodidae), to the conservation of endangered flora in the Galápagos islands prompted conservation groups to assess the risks associated with the introduction of its natural enemy, Rodolia cardinalis (Mulsant) (Coleoptera: Coccinellidae). Although R. cardinalis has been widely used for controlling this exotic pest, little information was found to confirm its presumed narrow feeding range. Consequently, studies were deemed necessary to determine whether the introduction of R. cardinalis would harm the island’s native invertebrate fauna, in particular rare or threatened species. Using no-choice trials, we tested neonate and third instar larvae of R. cardinalis against 16 and 11 potential prey species, respectively. Adults with prior feeding experience on I. purchasi were tested against eight non-target species and naïve adults (those that had not fed on I. purchasi) were tested against six. These trials included up to 35% of the Homoptera species of conservation value presumed to have the highest risk of being preyed upon by R. cardinalis. To maximize the range of species exposed to R. cardinalis, feeding trials were also carried out with some introduced species representative of groups containing potential non-target species that were not located for testing. R. cardinalis was unable to complete its life cycle on any of the test prey species and only fed on Margarodes similis Morrison (Homoptera: Margarodidae), a species closely related to the cottony cushion scale. M. similis, however, is subterranean and in its natural habitat is not at risk from foraging by R. cardinalis. Based on these trials, we believe that immature stages of R. cardinalis will have no impact on the non-target invertebrate fauna of the Galápagos islands because they specialize on Margarodidae. Although the limited nature of our testing prevents us from reaching a definitive conclusion about the prey range of R. cardinalis adults, our results indicate that it is also narrow. According to our field and laboratory studies, niche overlap with native predators of Homoptera will be minimal and intraguild predation should not occur.     

The role of natural enemies in controllingIcerya purchasi in South Australia

The obscure occurrence of the cottony-cushion scaleIcerya purchasi Maskell in its native country Australia is generally attributed to its natural enemies. Twelve natural-enemy-exclusion experiments were conducted at monthly intervals to confirm the role of natural enemies. Each experiment had uncaged, open-caged, and caged treatments. The natural enemies were active throughout the year. The percentage of scales surviving to adults in the cages was significantly higher than in the open-caged treatments, except the April (first) cohort. In both open-caged and uncaged treatments, the percentage of scales surviving to adults was similar and matched the changes in the numbers of natural enemies, thus confirming their importance in controllingI. purchasi in South Australia.      

Parasitization of the cottony-cushion scale in relation to host size

Measurements of body length of cottony-cushion scales,Icerya purchasi Maskell, are presented. Although length increased markedly with developmental stage, the length distributions of successive stages were found to overlap, making length an imperfect indicator of stage andvice versa. The likelihood of parasitism by the fly,Cryptochaetum iceryae (Williston), was found to increase with increasing scale size when scales of different sizes were concurrently made available to the parasites under field conditions. Also, parasite loads (no. of parasites per parasitized host) were found to increase with host size. The size ofC. iceryae pupae was found to depend on the developmental stage of the scale host in which pupation took place — the more developed (larger) the host, the larger the pupa. This result suggests that parasite growth is food limited in the smaller hosts, and that therefore its apparent preference for larger hosts is to the parasite's advantage.      

The allocation of searching time by Trichogramma pretiosum in host-containing patches

Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae), a generalist parasitoid of lepidopteran eggs, intensifies search in patches contaminated by a kairomone associated with Heliothis zea (Boddie) (Lepidoptera: Noctuidae) oviposition sites. In the laboratory the parasitoid will search any kairomone-treated patch, abandoning standardized (10 cm diam) patches if no hosts are located within 60–180 sec. Total time and searching time on patches in which hosts are discovered are more highly correlated with the number of hosts attacked (N_ha) per patch than with actual host density. The parasitoid's perception of host density per patch is often incorrect in this sense. Handling time (T_h) and time wasted in re-handling hosts parasitized earlier in the patch visit consume a large proportion of total patch time. Several hypotheses which have been suggested to explain patch time allocation by other parasitoids and predators appear inapplicable to T. pretiosum. The ratio of re-encounters with parasitized hosts to the number of hosts attacked appears to affect the allocation of patch time by this species. The results of previous field experiments are compared to laboratory observations of searching behavior.

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Résumé Trichogramma pretiosum Riley, parasitoïde généraliste des oeufs de lépidoptères, intensifie sa prospection sur des emplacements, contaminés par une kairomone associée aux pontes d'Heliothis zea Boddie (Lep. Noctuidae). Au laboratoire T. pretiosum cherchera les emplacements contaminés, abandonnant les morceaux de papier filtre standardisés (de 10 cm de diamètre) si aucun hôte n'est découvert dans les 60 à 180 secondes. Le temps total et le temps de prospection passés sur les emplacements sur lesquels des hôtes ont été découverts présentent une meilleure corrélation avec le nombre d'hôte attaqués (N_ha) par morceau de papier qu'avec la densité réelle des hôtes. La perception de la densité d'hôte par morceau de papier est souvent incorrecte dans ce sens. Le temps de palpation (T_h) et le temps dépensé à palper à nouveau des hôtes déjà parasités correspondent à une dépense importante du temps passé sur le morceau de papier. Les différentes hypothèses qui ont été utilisées pour expliquer la distribution du temps de prospection par d'autres parasitoïdes et prédateurs semblent inapplicables à T. pretiosum. Le taux de retour sur des hôtes parasités par rapport au nombre d'hôtes attaqués semble affecter les dépenses de temps de cette espèce. Les résultats d'observations antérieures dans les champs sont comparés aux observations de laboratoire du comportement de prospection.

     

Spontaneous activity of the light-dependent channel irreversibly induced in excised patches from Limulus ventral photoreceptors

We have studied the properties of membrane patches excised from the transducing lobe of Limulus ventral photoreceptors. If patches are excised into an "internal" solution that resembles the ionic composition of the cytoplasm, channel activity is typically absent, but can be turned on by cyclic GMP (cGMP). In contrast, if patches are excised directly into sea water and subsequently examined in internal solution, they exhibit a high channel activity in the absence of any second messenger (spontaneous channel activity). Because these patches contained only light-dependent channels when examined before excision and because these spontaneous channels have properties in common with the light/cGMP-dependent channel, we believe that the spontaneously active channels represent light/cGMP-dependent channels that have been damaged by exposure to sea water, perhaps due to proteolysis activated by the high Ca2+ levels of the sea water. One type of the spontaneously active channel resembles the light/cGMP-dependent channel in open time, reversal potential, conductance states and voltage dependence. Application of micromolar Ca2+ to this channel produces a reversible decrease in the opening rate, indicating a high affinity binding site for Ca2+ on this channel. Another type of spontaneously active channel has a conductance state and reversal potential similar to the light/cGMP-dependent channel, but has apparently lost its dependence and sensitivity to Ca2+ and voltage.     

Predatory behavior in the genusLeptogenys: A comparative study

We studied the predatory behavior of seven species of the genusLeptogenys from Mexico and Cameroon. The ants of this genus are armed with long, thin, curved mandibles articulated at the extreme corners of the anterior margin of the head, permitting them easily to seize oniscoid isopods, the obligate or the principal prey of mostLeptogenys species. Workers hunt these prey, which are able to roll themselves up, solitarily. Foraging behavior comprises sequences of up to eight activities. The prey can be seized by the body (rolled up or not), or alternatively by the edge of the shell, then turned over and stung on the ventral face. A relationship between the mandible size of the workers and the handling method permitted us to established that the phase “seizure by the edge of the shell” (compared to grasping the prey by the body) was more frequent as the prey size increased or the mandible length of the workers decreased. The rate of prey escape followed the same pattern. When a prey escaped, workers reacted by using a local searching or “reserve” behavior: they moved by increasing both sinuosity and speed. Recruitment occurred mainly after a worker found a group of prey or a large prey.L. mexicana are attractive at a distance to the isopods Bathytropidae living in the same natural environment. As a consequence, prey capture is possible without foraging for this species.     

防除狼毒对狼毒斑块植物-土壤C、N、P化学计量特征的影响

使用化学除草剂防除狼毒能有效遏制狼毒种群的扩张,对于防除狼毒后狼毒斑块的植被和土壤生态化学计量特征的研究鲜有报道。基于此,本研究运用生态化学计量学的原理、方法,以分枝数相同的单株狼毒（Stellera chamaejasme）斑块为研究对象,通过化学药剂防除狼毒后,分析狼毒斑块内外植物-土壤C、N、P含量及其比值的变化,探讨植物和土壤化学计量特征的内在联系以及狼毒斑块的养分循环规律,为狼毒型退化草地的生态恢复及利用提供参考。结果表明：防除狼毒后禾本科生物量有所增加,豆科和杂类草地上生物量显著低于狼毒斑块内（P<0.05）。不同狼毒斑块的豆科植物N含量和杂类草P含量最高,防除狼毒后植物C、N含量高于其他斑块;禾本科P含量为狼毒斑块外显著高于狼毒斑块内（P<0.05）;狼毒斑块内外莎草科C∶N显著高于防除狼毒（P<0.05）;莎草科和豆科C∶P和N∶P为防除狼毒显著高于狼毒斑块内和狼毒斑块外（P<0.05）,杂类草C∶P和N∶P为防除狼毒显著高于狼毒斑块外（P<0.05）,禾本科C∶P为狼毒斑块内显著高于防除狼毒和狼毒斑块外（P<0.05）。不同狼毒斑块土壤C、P含量以及C∶P表现为狼毒斑块内>狼毒斑块外>防除狼毒,N含量和N∶P为防除狼毒>狼毒斑块内>狼毒斑块外,C∶N表现为狼毒斑块内和狼毒斑块外显著高于防除狼毒（P<0.05）。冗余分析（RDA）结果显示植物与土壤的C,C∶N,C∶P,N∶P两两显著正相关,N,P两两显著负相关,且防除狼毒后对植物和土壤的N含量,N∶P以及植物P含量影响较大。     

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.     

Effect of Starvation on the Searching Path of the Predatory Bug <Emphasis Type="Italic">Deraeocoris Lutescens</Emphasis>

As physiological factors may influence the predatory behavior of insects, this study was designed to evaluate the possible impact that hunger has on the search path of a polyphagous predator: Deraeocoris lutescens Schilling (Heteroptera: Miridae). D. lutescens was fed a diet of Rhopalosiphum padi (Linné) (Homoptera: Aphididae) nymphs and Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs at 21±1 °C and a photoperiod of 16:8 (L:D). After moulting, third and fifth instar nymphs and adults were placed in Petri dishes containing an abundant food source for 24 h. After 24 h, the food was removed and groups were randomly assigned to increasing periods of prey deprivation. Each D. lutescens nymph or adult was placed at the center of an empty arena and its searching path was recorded to calculate different path parameters and to determine the type of movement mode adopted. Results show an effect of starvation on both nymphal and adult D. lutescens searching paths. Satiated third instar nymphs manifested an intensive search path whereas fifth instar nymphs and adults adopted an intermediate one. When starved, the extensive search path appeared early in young nymphs, and later in the last instar nymphs and adults, according to the degree of prey deprivation.     

The effect of hunger level on predation dynamics in the spider Nesticodes rufipes: a functional response study

It is well known that a predator has the potential to regulate a prey population only if the predator responds to increases in prey density and inflicts greater mortality rates. Predators may cause such density-dependent mortality depending on the nature of the functional and numerical responses. As spiders are usually faced with a shortage of prey, the killing behavior of the spider Nesticodes rufipes at varying densities of Musca domestica was examined here through laboratory functional response experiments where spiders were deprived of food for 5 (well-fed) or 20 days (hungry). An additional laboratory experiment was also carried out to assess handling time of spiders. The number of prey killed by spiders over 24- and 168-h periods of predator–prey interaction was recorded. Logistic regression analyses revealed the type II functional response for both well-fed and hungry spiders. We found that the lower predation of hungry spiders during the first hours of experimentation was offset later by an increase in predation (explained by estimated handling times), resulting in similarity of functional response curves for well-fed and hungry spiders. It was also observed that the higher number of prey killed by well-fed spiders over a 24-h period of spider–prey interaction probably occurred due to their greater weights than hungry spiders. We concluded that hungry spiders may be more voracious than well-fed spiders only over longer time periods, since hungry spiders may spend more time handling their first prey items than well-fed spiders.     

A comparative study on the phylogenetic diversity of culturable actinobacteria isolated from five marine sponge species

A cultivation-based approach was employed to compare the culturable actinobacterial diversity associated with five marine sponge species (Craniella australiensis, Halichondria rugosa, Reniochalina sp., Sponge sp., and Stelletta tenuis). The phylogenetic affiliation of the actinobacterial isolates was assessed by 16S rDNA-RFLP analysis. A total of 181 actinobacterial strains were isolated using five different culture media (denoted as M1–M5). The type of medium exhibited significant effects on the number of actinobacteria recovered, with the highest number of isolates on M3 (63 isolates) and the lowest on M1 (12 isolates). The genera isolated were also different, with the recovery of three genera on M2 and M3, and only a single genus on M1. The number of actinobacteria isolated from the five sponge species was significantly different, with a count of 83, 36, 30, 17, and 15 isolates from S. tenuis, H. rugosa, Sponge sp., Reniochalina sp., and C. australiensis, respectively. M3 was the best isolation medium for recovery of actinobacteria from S. tenuis, H. rugosa, and Sponge sp., while no specific medium preference was observed for the recovery of actinobacteria from Reniochalina sp., and C. australiensis. The RFLP fingerprinting of 16S rDNA genes digested with HhaI revealed six different patterns, in which 16 representative 16S rDNAs were fully sequenced. Phylogenetic analysis indicated that 12 strains belong to the group Streptomyces, three strains belong to Pseudonocardia, and one strain belongs to Nocardia. Two strains C14 (from C. australiensis) and N13 (from Sponge sp.) have only 96.26% and 96.27% similarity to earlier published sequences, and are therefore potential candidates for new species. The highest diversity of three actinobacteria genera was obtained from Sponge sp., though the number of isolates was low. Two genera of actinobacteria, Streptomyces, and Pseudonocardia, were isolated from both S. tenuis and C. australiensis. Only the genus of Streptomyces was isolated from H. rugosa and Reniochalina sp. Sponge species have been demonstrated here to vary as sources of culturable actinobacterial diversity, and the methods for sampling such diversity presented may be useful for improved sampling of such diversity.     

Characterization of plant-growth promoting diazotrophic bacteria isolated from field grown Chinese cabbage under different fertilization conditions

Diazotrophic bacteria isolated from the rhizosphere of Chinese cabbage were assessed for other plant growth promoting characteristics viz., production of IAA, ethylene, ACC deaminase, phosphate solubilization, and gnotobiotic root elongation. Their effect on inoculation to Chinese cabbage was also observed under growth chamber conditions. A total of 19 strains that showed higher nitrogenase activity identified by 16S rRNA gene sequence analysis were found to be the members of the genera Pseudomonas and Agrobacterium belonging to α- and γ-Proteobacteria groups. These strains were also efficient in producing IAA and ACC deaminase though they produced low levels of ethylene and no phosphate solubilization. In addition, inoculation of selected diazotrophic bacterial strains significantly increased seedling length, dry weight, and total nitrogen when compared to uninoculated control. The colonization of crop plants by diazotrophic bacteria can be affected by many biotic and abiotic factors, and further studies are oriented towards investigating the factors that could influence the establishment of a selected bacterial community.     

A newOphiostoma species isolated from Japanese oak infested byPlatypus quercivorus

A newOphiostoma species was isolated from the sapwood ofQuercus mongolica var.grosseserrata and described asOphiostoma longicollum sp. nov. The species is characterized by a long perithecial neck with a gelatinous cap at the apex and a constricted base, orange-section-shaped ascospores that accumulate in a yellow-orange drop at the apex of the neck, and itsSporothrix anamorph. Contribution No. 137, Laboratory of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba.     

A numerical taxonomic study of some pigmented bacteria isolated from Organic Lake,an antarctic hypersaline lake

A study was made of a group of moderately halophilic, heterotrophic, pigmented strains isolated from Organic Lake, Antarctica. These strains were Gram-negative, non-motile, had an aerobic metabolism and a mol% G+C content of their DNA in the range 35–41, indicating that they may be members of the Flavobacterium-Cytophaga group. A numerical taxonomic study involving 134 characteristics compared the antarctic strains with reference strains from Flavobacterium, Cytophaga and Flectobacillus. The antarctic strains formed two clusters that did not contain any reference strains suggesting that they may represent two new species of the genus Flavobacterium.     

Larval mortality of pine sawflies [Hymenoptera: Diprionidae] in relation to pollution level: A field experiment

Larval mortality ofNeodiprion sertifer (Geoffroy),Diprion pini (L.) andGilpinia pallida (Klug) were studied in field experiments around a factory complex in southwestern Finland. Larval colonies were transferred on the shoots of Scots pines growing at different distances from the emission source. Larval mortality was highest near the factories. InN. sertifer, larval mortality caused by the nuclear polyhedrosis virus was higher and cocoon mortality caused by parasitoids was lower near the pollutant source. The most abundant parasitoid species wereSynomelix scutulata (Hartig) andLamachus eques (Hartig). 16–67% of theN. sertifer, 0–5% of theD. pini and the 73–100% ofG. pallida cocoons contained parasitoids oviposited during the larval period of the sawflies.      

Orientation behaviour of the predatory hemipteran Perillus bioculatus to plant and prey odours

The pentatomid predator P. bioculatus responded by positive odour-conditioned anemotaxis when exposed to airborne volatiles emitted by potato plants damaged by Colorado potato beetle larvae, whereas intact potato plants and non-feeding larvae as odour sources failed to elicit anemotaxis. Walking tracks of adult predators had higher values of straightness and upwind fixation when odours emanating from mechanically damaged plants were encountered than tracks registered in response to air carrying volatiles from intact plants, but these parameters returned to control values within 1–2 h after damage was caused. In contrast, air led over plants damaged by beetle larvae elicited orientation responses at least 3 hours after feeding damage ceased. The combination of chemical data on headspace composition, olfactory sensitivity established in electro-antennogram studies and behavioural data presented here imply a role of sesquiterpenoid plant volatiles as odorous cues eliciting attraction of this predator to damaged potato plants.     

A new genetically isolated population of theSaccharomyces sensu stricto complex from Brazil

Genetic and karyotypic studies of someSaccharomyces sensu stricto yeasts from Brazil revealed a genetically isolated population which apparently represents a new sibling species ofS. cerevisiae.     

基于野外观测检验动物廊道选址模型的准确性——以白头叶猴为例

廊道构建是减少栖息地破碎化负面影响的重要策略之一。目前,已经有许多模型用于动物廊道的选址,而"选址模型是否能准确预测动物迁移的实际发生位置"一直是保护生物学最为关注的问题。最小成本路径模型（LCP）和条件最小成本廊道模型（CMTC）是两种较为常用的廊道选址模型。以白头叶猴（Trachypithecus leucocephalus）为目标物种,分别运用LCP和CMTC模拟生成白头叶猴迁移廊道,将模拟结果与野外观测廊道进行对比,检验两种方法的准确性。结果表明：与野外观测实际廊道相比,LCP模型模拟结果的完全准确率为46.7%,部分准确率为20%,完全不准确率为33.3%;CMTC模型模拟结果的完全准确率为26.7%,其余73.3%为部分准确,无完全不准确的结果;总体上看,CMTC廊道的准确率较LCP高,因而CMTC模型模拟白头叶猴实际迁移廊道位置的准确性优于LCP模型。输入"源"要素类型、阻力面栅格尺度设定、栖息地土地利用类型变化以及动物迁移行为复杂性4个因素是影响该模拟结果准确性的主要原因。