Observations on feeding and oviposition in some British mosquitoes

Laboratory observations showed a significant positive correlation between the size of unfed females of Mansonia richiardii and Aedes cinereus and the quantity of blood ingested, but no correlation in Ae. detritus, Ae. punctor and Ae. cantans. There was also a positive correlation between the size of the blood-meal and number of eggs laid by Ae. cinereus and Ae. punctor, but not in Ae. detritus, Ae. cantans and M. richiardii. The number of eggs laid varied greatly between different species, Culex species laid most eggs. Most eggs of Ae. punctor hatched during the first three soakings, whereas in Ae. cinereus most hatched during the 8th–12th soakings. Egg hatching in Culiseta annulata, Culex, Mansonia and Anopheles species was sometimes spread over several days, in Cst. annulata up to 13 days. The duration of the gonotrophic cycle was investigated in several species. In Cst. annulata and Ae. detritus, which have long adult biting seasons, considerable variations occurred in its length at different times of the year.

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Zusammenfassung An einigen britischen Mücken wurden Laborbeobachtungen über Blutaufnahme und Eiablage durchgeführt. Die Größe der Blutmenge, die Mansonia richiardii, Aedes cinereus, Ae. detritus, Ae. punctor, Ae. cantans und Culiseta annulata Aufnahmen, wurden mit gravimetrischen Methoden ermittelt. Nur bei M. richiardii (P<0,001) und Ae. cinereus (0,001Ae. dorsalis, Ae. geniculatus, C. morsitans, C. litorea, Anopheles claviger, A. plumbeus, Culex pipiens und C. torrentium abgelegt wurden, wurden bestimmt. Die beiden letztgenannten Arten legten im Mittel 248 bzw. 244 Eier. Andere Arten Legten weniger Eier, die kleinsten mittleren Gelege (52) wurden von Ae. contans produziert. Bei Ae. punctor und Ae. cinereus wurden mehr Eier von den Individuen produziert, welche die größten Blutmahlzeiten eingenommen hatten (0,02Ae. punctor wurden 86% der Eier nach den ersten drei Blutmahlzeiten produziert, bei Ae. cinereus jedoch keine, die schlupffähig waren. 74% der Ae. cinereus-Eier schlüpften während der 8.–12. Blutaufnahme. Eier von C. annulata, M. richiardii, Culex- und Anopheles-Arten schlüpften während mehrerer Tage, bei C. annulata bis zu dreizehnDie Dauer der gonotrophen Zyklen unterlag bei Ae. detritus und C. annulata beträchtlichen monatlichen Schwankungen. Während Juni bis August betrug sie bei den meisten Arten 5 bis 7 Tage, bei M. richiardii im August jedoch im Mittel 9,8 Tage.

     

Predation-related odours reduce oviposition in a herbivorous mite

When adult females of the herbivorous mite, Tetranychus urticae, were exposed to the predatory mite, Phytoseiulus persimilis, they laid fewer eggs than females that had not been exposed to P. persimilis when transferred onto a new leaf patch. However, when T. urticae females were exposed to either products of P. persimilis or artificially damaged conspecific eggs on a leaf patch, the number of T. urticae eggs on a new leaf patch did not differ significantly from the control. The reduced oviposition was neither due to the feeding activity on the leaf patch with P. persimilis nor to that on the new leaf patch. There was also no significant difference between the number of T. urticae eggs produced on a new leaf patch following exposure to the odours of a neighbouring leaf patch where there had previously been either P. persimilis or T. urticae adults. However, female T. urticae that had been exposed to odours from neighbouring leaf patches on which both T. urticae and P. persimilis had been placed produced significantly fewer eggs on a new leaf patch than those that had not been exposed to such odours. Neither odours from neighbouring intact leaf patches on which T. urticae eggs were preyed on by P. persimilis, nor odours from a neighbouring Parafilm patch on which T. urticae was preyed on by P. persimilis affected the oviposition of T. urticae. These data suggest that the presence of T. urticae, P. persimilis and a leaf patch are needed for the emission of odours to reduce oviposition in T. urticae.     

有性棉蚜交配和产卵习性的观察

有性棉蚜有多次交配习性,交配时间平均为41分钟。雌蚜寿命为28．1±6．0天,产卵前期为3．0±1．2天,产卵历期为15．3±3．8天,产卵后期为9．7±3．4大,每雌产卵8．1±1．6粒,卵的产出率平均为88．4％。群体产卵的始盛、高峰和盛末期分别在羽化后3～4天、7～8天和15～16天。未经交配的雌蚜在产卵方面有明显的负效应,产出的受精卵也不能孵化。     

Wolbachia affects oviposition and mating behaviour of its spider mite host

Wolbachia bacteria are transmitted from mother to offspring via the cytoplasm of the egg. When mated to males infected with Wolbachia bacteria, uninfected females produce unviable offspring, a phenomenon called cytoplasmic incompatibility (CI). Current theory predicts that ‘sterilization’ of uninfected females by infected males confers a fitness advantage to Wolbachia in infected females. When the infection is above a threshold frequency in a panmictic population, CI reduces the fitness of uninfected females below that of infected females and, consequently, the proportion of infected hosts increases. CI is a mechanism that benefits the bacteria but, apparently, not the host. The host could benefit from avoiding incompatible mates. Parasite load and disease resistance are known to be involved in mate choice. Can Wolbachia also be implicated in reproductive behaviour? We used the two‐spotted spider mite – Wolbachia symbiosis to address this question. Our results suggest that uninfected females preferably mate to uninfected males while infected females aggregate their offspring, thereby promoting sib mating. Our data agrees with other results that hosts of Wolbachia do not necessarily behave as innocent bystanders – host mechanisms that avoid CI can evolve.     

Influence of dietary improvement on oviposition and egg viability of the mite, Tetranychus urticae

New formulations of a chemically defined diet on which Tetranychus urticae has been reared resulted in a pre-oviposition period being shortened from 3·5 to 1·5 days, an oviposition rate increased from 0·343 to 0·649 egg/female mite per day and an oviposition period extended from 25 to 36 days, and egg viability increased from 3·6 to 19·2 per cent hatchability. These formulations included deletion of cholesterol from the diet and inclusion of plant sterols only, a higher level of total sterols combined with a lower level of total fatty acids, and the addition of vitamin E (alpha tocopherol).     

Effect of polypeptide initiation factors on the spermidine stimulation of initiation complex formation

The AUG- and MS2 RNA-dependent fMet-tRNA binding to 30S ribosomal subunits was stimulated by spermidine with any individual or combination of initiation factors capable of participating in the formation of an initiation complex. When 70S ribosomes were used instead of 30S ribosomal subunits, IF-3 was necessary for spermidine stimulation of the complex formation.     

非嗜食植物提取物对桔全爪螨产卵的驱避性测定

The oviposition repellency of the alcohol extracts from 50 species of non-preferable plants and azadirachtin against citrus red mite ( Panonychus cirri ) was determined using laboratory bioassays. In choice tests, the extracts from 42 of the 50 plant species and 1% azadirachtin (2000×) significantly reduced oviposition 1d after treatment.The repellency effect of the extracts from the 42 plant species was better than that of azadirachtin. Mikania micrantha extract had the best result, with an Interference Index of Population Control (IIPC) of 0.087 1 d after treatment, and significantly reduced oviposition for 9 d, while the extracts from Sesbania cannabina, Allium tuberosum , Paederia scandens , Duranta erecta and Dicranopteris pedata also had good effects, with an oviposition repellency of over 70 % 1 d after treatment, and significantly reduced oviposition for 4 - 6 d. The effect became weaker as time went on. None of the extracts showed significant oviposition attraction.     

Observations on the integument of the water mite Arrenurus major (Acari: Parasitengona)

A study of the integument of the aquatic mite Arrenurus major Marshall is presented. When the cuticle is examined with the unaided eye and the light microscope, it appears to possess numerous tiny pits. However, scanning electron micrographs of the cuticle reveal that it is a solid surface with topographical sculpturing of the epicuticle, indicating that the “pits” are an internal phenomenon. In cuticle which has been sectioned, areas devoid of cuticular material beneath the thin exocuticle are revealed. These areas are the pits which are goblet-shaped. The integument consists of five major strata. These are from the outside to the inside: (1) a superficial layer with a maximum observed thickness of 725 Å, (2) an epicuticle with a thickness of about 900 Å and composed of at least four sublayers, (3) an exocuticle with a thickness of about 1.5 Å. Fibers of the exocuticle are arranged in a Bouligand pattern and exhibit a regularly occurring discontinuity with a spacing of 200 Å. (4) An endocuticle ranging from 15 to 20 μ in thickness. The endocuticle is characterized by bandings which superficially resemble the lamellae of insects but are not homologous, microfibers which exhibit a preferred orientation, and the presence of the pits; and (5) an epidermis lying beneath the endocuticle and extending into the pits. Pore canals are present only in the exocuticle and have their origin at the apices of the pits. The pore canals contain a central filament, and a plug is present just beneath the epicuticle.     

Exudate from sporulating cultures of Hirsutella thompsonii inhibit oviposition by the two-spotted spider mite Tetranychus urticae

The acaricidal mycopathogen Hirsutella thompsonii has been found to secrete metabolites that are active against femaleTetranychus urticae. Specifically, the rose-colored exudate produced on sporulating cultures of Mexican HtM120I strain sterilized female spider mites in a dose-dependent fashion. Topical application of the exudate resulted in a 100% reduction in mite fecundity over the initial six days of experimentation. Depending upon the exudate dosage, mites partially recovered within 3 and 6 d post-treatment and produced a limited number of eggs. The spider mite active HtM120I exudate contained less detectable HtA toxin than the HtM120I broth filtrate, and it was innocuous when injected into the greater wax moth Galleria mellonella L. larvae. Broth filtrates of HtM120I cultures, although toxic to assayed G. mellonella larvae, did not inhibit mite oviposition to the degree or duration of the exudate preparations. These findings suggest that the factor responsible for suppressing oviposition in female spider mites is linked to the sporulation process and is distinct from the well-characterized HtA produced by vegetative cells. This revised version was published online in July 2006 with corrections to the Cover Date.     

Observations on the control of Tetranychus urticae koch on cucumbers by the predatory mite Phytoseiulus riegeli dosse

The interaction between Tetranychus urticae and Phytoseiulus riegeli on cucumbers was studied in several different experiments at two centres. It was shown that if the predator is introduced at a low prey population, elimination of the mites occurred before leaf-injury became sufficiently high to cause a reduction in cucumber yield. A theoretical pattern of mite control and leaf-damage is discussed, and it is concluded that economic control should follow two introductions of Phytoseiulus during the first 25 weeks of a cucumber crop. As the predator does not diapause, acaricidal control should be used for the remainder of the economic life of the crop if leaf-damage approaches the critical level.

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Zusammenfassung Verschiedene, in zwei Arbeitszentren ausgeführte Untersuchungen über die Bekämpfung von Tetranychus urticae mit Phytoseiulus riegeli werden diskutiert. Es wird gezeigt, daß der Räuber über einen weiten Spielraum der Beutepopulation, gemessen am Ausmaß der Blattbeschädigung, innerhalb von 5 Wochen zur Herrschaft gelangt. Wo Phytoseiulus in eine kleine Beutepopulation eingeführt wird, erfolgt deren Auslöschung stets bevor der Blattschaden so hoch wird, daß eine Ertragseinbuße im Gurkenfeld entsteht. Unter solchen Umständen wurde der Räuber bis zu 8 Wochen nach dem Einsetzen überlebend gefunden.Auf Grund der Ausmaße der Blattbeschädigung, die sich in diesen Untersuchungen vor und nach der Unterdrückung des Schädlings ergaben, wurde ein theoretisches Programm einer integrierten akariciden und biologischen Bekämpfung ausgearbeitet. Dieses nimmt an, daß zwei Einführungen des Räubers (oder eine der Räuber, der eine der Beute folgt, bevor jener ausstirbt) für die ersten 25 Wochen der Gurkenentwicklung eine ökonomische Bekämpfung ergeben. Da der Räuber offensichtlich nicht diapausiert, sollte während der letzten Stadien des Gurkenaufwuchses ein Akaricid-Einsatz folgen.

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Previously at N.A.A.S., Cambridge.     

Effect of cannibalism on predation,oviposition and longevity of the predacious mite,Agistemus exsertus Gonzalez (Acari: Stigmaeidae)

Cannibalism (intraspecific predation) on conspecific eggs was investigated in the predatory stigmaeid mite, Agistemus exsertus Gonzalez in the absence of eggs of Tetranychus urticae Koch (no-choice tests) and presence of three densities of prey eggs simultaneously (choice tests) in the laboratory. Data show that cannibalism occurs in immatures and adult females of the predator, which successfully developed and reproduced on conspecific eggs as an alternative prey in the absence of prey eggs. In no-choice tests, cannibalism rate on conspecific eggs by A. exsertus stages was significantly lower than the predation rate on T. urticae eggs. The predatory mite exhibited a marked decline in oviposition rate when preyed on conspecific eggs compared with feeding on prey eggs. The developmental duration and longevity of A. exsertus females were significantly longer 1.9 and 1.7 times, respectively, when fed on conspecific eggs than feeding on T. urticae eggs. The propensity of the predator towards cannibalism depends on the prey density, when T. urticae eggs and conspecific eggs are present simultaneously. Provision of increased densities of prey eggs significantly decreased cannibalism and predation by A. exsertus stages, which fed generally less on conspecific eggs than on T. urticae eggs in choice tests. The oviposition rate of the predator increased significantly, as the egg density of the prey increased. The developmental period and longevity of A. exsertus females showed significantly gradual shortness with increasing egg density of the prey.     

Observations on the mite fauna associated with adult Stomoxys calcitmns in the U.K.

Abstract. Adult females of the blood-sucking muscid Stomoxys calcitrans sampled between June and September 1993 from a cattle farm ( n = 839) and from a pig farm ( n = 542) in North-West England were examined for mites. Twelve species of mites from ten families and three orders were identified as follows. In the Prostigmata, Eryenetes sp., Family Ereynetidae and Pediculaster mesembrinae , Family Pygmephoridae. In the Astigmata, Procalvolia zacheri Family Saproglyphidae, Acarusfarris , Family Acaridae, Bonomoia sphaerocerae and Myianoetus sp., Family Anoetidae. In the Mesostigmata, Macrocheles muscaedomesticae and Macrocheles subbadius Family Macrochelidae, Digamasellus sp., Family Digamasellidae, Halolaelaps sp., Family Halolaelapidae. Prodinychus sp., Family Uropodoidea and Thinoseius sp., Family Eviphididae. Mean infestation rates at the two sites (all mite species) for the entire sampling period were 31.6 ± 13.9% and 19.8 ± 3.6% respectively. 51 % of synbovine flies sampled in July were infested with mites. Mean numbers of flies infested in August at both farms were significantly lower compared to other months. The presence of tritonymphs of Ereynetes sp. on S.calcitrans demonstrates for the first time that this life cycle stage is naturally associated with insects in the field.
All mites were recovered from the ventral thorax and abdomen, and two or more species commonly infested individual flies. Associations of mites with their dipteran hosts are described and discussed.     

Pear rust mite,Epitrimerus pyri (Acari: Eriophyidae) oviposition and nymphal development on Pyrus and non-Pyrus hosts

The ovipositional response of deutogynes of the pear rust mite, Epitrimerus pyri Nalepa, and the rate of development of E. pyri nymphs differed according to the host plant to which mites were exposed. Among the fourteen Pyrus hosts examined, leaves from the Clapp's Favorite cultivar of P. communis elicited the strongest egg-laying response and the fastest rate of nymphal development, whereas egg-laying was least and nymphal development slowest on leaves from P. calleryana. Among the three non-Pyrus hosts, E. pyri oviposited and completed nymphal development on apple and quince leaves, but would not deposit eggs on apricot. Antixenosis appears to be the primary mechanism of resistance, although antibiosis may be operating to a lesser extent. These results are discussed in relation to the resistance of Pyrus to other arthropod pests.     

Observations on the oviposition behaviour of frit fly (Oscinella frit L. dipt. chloropidae)

Two separate groups of stimuli (1) originating from the plant, (2) proprioceptive, have been found to mediate egg laying. An artificial shoot has been devised to investigate oviposition behaviour.

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Zusammenfassung Die Eiablage wird durch eine Anzahl von Reizen ausgelöst, die nacheinander wirken, jedoch im einzelnen nicht genauer identifiziert wurden. Sie lassen sich jedoch in zwei Gruppen trennen: (1) Reize, die von der Wirtspflanze selbst ausgehen und (2) solche, die wahrscheinlich propriorezeptiv wirken und auf der Notwendigkeit einer geeigneten Haltung der Beine und des Legeapparates während des Eiablageaktes beruhen.Die propriorezeptiven Reize scheinen die Fliegen häufig von den Keimpflanzen weg und zur Ablage ihrer Eier auf dem Boden zu führen, was darauf hindeutet, daß die Eier im Freien in ähnlicher Weise in den Erdboden abgelegt werden.Ein Extrakt aus in Wasser zerriebenen Haferpflanzen scheint in Verbindung mit einer geeigneten Oberfläche (z.B. Erdboden oder Sand) Eiablageverhalten auszulösen. Verschiedene Resultate wurden mit glatt oder rauh strukturierten Oberflächen und in Abhängigkeit von Gegenwart oder Abwesenheit des Extraktes erhalten. Die Reaktion der Fliegen scheint mit dem physiologischen Zustand des Gewebes zu variieren, das den Fliegen geboten wird, und das Eiablageverhalten ist schwach, wenn den Fliegen alte oder absterbende Pflanzenteile geboten werden. Die Wahrscheinlichkeit, daß Reize, welche Nahrungsaufnahme, und solche, die Eiablage hervorrufen, ursprünglich nicht die gleichen sind, ist nur gering.Eine künstliche Keimpflanze, die von den Fliegen zur Eiablage ebenso angenommen wurde wie eine junge, gesunde, lebende, wurde dadurch hergestellt, daß ein dreieckiges Stück Fließpapier mit Haferextrakt befeuchtet und in das Innere einer 2,5×2,5 cm Glastube gesteckt wurde.

     

Observations on pollen processing byPneumolaelaps longanalis (Acari: Laelapidae), a mite associate of bumblebees

Pneumolaelaps longanalis feeds on nectar and surface compounds of bumblebee-collected pollen grains by dissolving these materials in salivary secretions applied to the grain as it is manipulated by the mite's mouthparts. Observations suggest that sugars applied to the pollen grain during bee-processing serve as a feeding stimulus for the mite.Supported by a Grant-in-Aid of Research from Sigma Xi, the Scientific Research Society of North America. Technical Paper 8461, Oregon Agricultural Experiment Station.     

Effects of mite age, mite density, and host quality on aerial dispersal behavior in the twospotted spider mite

Mite age, population density, and host leaf quality affect various life history traits in spider mites. We investigated the effects of these factors on the aerial dispersal behavior of adult female twospotted spider mites,Tetranychus urticae Koch (Acari: Tetranychidae). The proportion of adult females exhibiting the dispersal behavior dropped significantly with age following adult emergence, particularly in the first 3 days. Sixty to eighty percent of female mites 2-days old or younger displayed the behavior under test conditions, whereas less than 20% of female mites older than 3-days-old showed the behavior. Younger adult females also exhibited shorter latency for the behavior, although this trend was not as clear. Leaf quality experienced during deutonymph development had no effect on the behavior adults subsequently displayed. On the other hand, adult females that fed on poor quality leaves after emergence were twice as likely to display the behavior (90% vs. 45%), and with shorter latency (37 vs. 77 min), than those that fed on high quality leaves. When newly emerged adult females encountered high mite density and dry leaves, the incidence of the behavior increased (69% vs. 47%) and latency decreased (69 vs. 93 min) compared to mites that encountered low density on well watered leaves. Our results suggest that both starvation and desiccation of adult females may enhance their dispersal behavior.