Life history stages and taxonomy of Austrosimulium (Austrosimulium) tillyardianum (Diptera: Simuliidae)

The male, female, pupa, 9th‐instar larva, and egg of Austrosimulium (Austrosimulium) tillyardianum Dumbleton, 1973, are redescribed, and larval instars one to eight are described and morphologically differentiated for the first time. The relationship of A. (A.) tillyardianum to other New Zealand species is briefly reviewed.     

Cytogenetics of New Zealand blackflies of the genus Austrosimulium (Diptera: Simuliidae) 1. The cytogenetics of Austrosimulium australense

Abstract

This study undertakes a cytogenetic analysis of the New Zealand blackfly species Austrosimulium australense (Schiner). The principles of such an approach are outlined, and previous taxonomic studies of the genus Austrosimulium, in particular the taxonomic position of A. australense, are discussed. Populations from North Island localities covering a wide area were sampled and analysed for polymorphisms in the polytene chromosomes, taken from salivary glands of larvae. In all, 1018 larvae from 49 sites were analysed. A polytene chromosome map of A. australense is presented, with details of chromosomal inversions found in salivary gland cells. Three geographical zones are designated, according to the incidence of certain chromosomal polymorphisms.     

The water velocity preferences of Austrosimulium furiosum and Simulium ornatipes (Diptera: Simuliidae) larvae,and the implications for micro-habitat partitioning

The aquatic larvae of two simuliid species, Austrosimulium furiosum (Skuse) and Simulium ornatipes Skuse, which often occur together in Victorian streams, were shown in laboratory experiments to have preferences for different water velocities: larvae of A. furiosum preferred water velocities of 0.2–0.3 m s^–1, and S. ornatipes preferred water velocities of 0.9–1.3 m s ^–1 . Final instar larvae of both species selected slow water speeds of less than 0.25 m s ^–1 prior to pupation. Flow patterns around a cylinder in a laboratory stream were mapped, and the distribution of A. furiosum larvae within the wake, paired vortices and horseshoe vortex was recorded. Larvae selected areas with suitable water velocities and aligned with the flow, providing flow visualization of micro-current speed and direction. The potential for micro-habitat partitioning is discussed in relation to benthic sampling strategies.     

Food selection of Tanytarsus gracilentus larvae (Diptera: Chironomidae): An analysis of instars and cohorts

Gut contents of the detritivorous Tanytarsus gracilentus larvae were studied at one site in Lake Myvatn, Iceland. Samples were collected with a sediment corer. Sediment samples were taken from the surface of the intact core before the larvae were collected. Gut contents were compared between different larval instars and cohorts, and to the surface sediment. The composition of the gut contents of all instars was different from that of the sediment surface. The first instar selected small diatoms of the genus Fragilaria, as single and paired cells, and the fourth instar selected detritus items of more variable size and origin. Apart from the third instar larvae, there were similar trends in food selectivity between the same instar of different cohorts. No major changes occurred in the composition of the surface sediment during the time of this study.     

Size selection of latex beads by blackfly larvae (Diptera: Simuliidae) in the laboratory

In laboratory experiments, blackfly larvae collected from a lake outlet, a woodland and a meadow stream were tested for size selection of latex beads of < Ito > 100 μm diameters. 3 suspensions of varying proportions for each size category were supplied to these blackfly larvae in common experiments. Comparisons between the size frequency distributions of particles supplied and the particle compositions in the larval guts showed intra- and interspecific differences and were quantified by calculating Jacobs' electivity index. In all species selection of larger particles increased with the larger larval instars. Although there was a positive selectivity of small particles in some cases, the ingested proportion of large particles increases volumes and biomasses of gut content and may be more important for larval growth than small particles.     

人工饲养背摇蚊幼虫龄数和龄期的测定

本文采用了人工饲养定期取样的方法,测定了背摇蚊Chironomus dorsalis(Anderson)幼虫的龄数以及各龄的龄期。分别测量不同发育阶段幼虫的头壳长、颏中齿顶端至冠突前缘间距离、头壳宽、颏宽、颏中齿宽、触角长、触角基节长、触角比(触角基节与其余各节的长度之比)等8项指标,以期得到区分和判定幼虫虫龄的最佳形态特征及指标。运用频次分布、均差分析和回归分析对8项指标测量数据进行统计分析,结果表明,背摇蚊幼虫可分4龄,触角长可作为理想的分龄特征和分龄指标,其次是颏中齿顶端至冠突前缘间距离和颏宽。利用种群众数龄期法计算1-4龄幼虫的平均龄期分别为1.32 d、2.00 d、7.51 d和8.39 d,幼虫期共为19.22 d。     

Use of inter-simple sequence repeat (ISSR) markers for discrimination between and within species of blackflies (Diptera: Simuliidae)

The present study is the first report of fingerprinting in blackflies (Diptera: Simuliidae), using inter-simple sequence repeat (ISSR) markers. Among five primers tested, three tetranucleotide repeat primers ((GACA)₄, (ACTG)₄, (ACAG)₄) generated a high proportion of polymorphic bands. Seven species representing various genera, subgenera or species groups were compared. No similar profiles were found. Intraspecific and interspecific banding patterns were analysed for two species in the Prosimulium hirtipes (Fries, 1824) species group and four species in the Simulium variegatum (Meigen, 1818) species group. The UPGMA cluster analysis based on Jaccard’s coefficient demonstrated the intraspecific and interspecific diversity and the resolving power of the ISSR markers to differentiate blackfly species and populations. In Simulium maximum (Knoz, 1961), geographically defined populations were successfully discriminated.     

Screening method for insecticidal activity using first instars of black blow fly (Diptera: Calliphoridae)

A bioassay method suitable for rapid mass screening of fermentation and synthetic organic compounds for insecticidal activity is described. The test, which uses first instars of susceptible black blow fly, Phormia regina (Meigen), in a bovine serum medium, detects insecticidal activity with reproducible results. It is capable of selecting the most active compound in structure-activity relationships by minimum effective dose concentration studies. The bioassay system is easy to operate and requires only a minute quantity of chemical compound.     

Application of a frequency distribution method for determining instars of Eucryptorrhynchus brandti (Coleoptera: curculionidae) from several morphological variables

Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae) is a major pest of Ailanthus altissima (Mill.) Swingle (Simaroubaceae), commonly known as tree-of-heaven, and A. altissima var. Qiantouchun in China. It is considered a potential biological control agent for tree-of-heaven in North America. The aim of this study was to use a frequency distribution method to determine the instars of field-collected larvae of E. brandti. We collected larval samples of various sizes from both the field and the laboratory and measured five morphological variables, including antenna spacing, mandible width, head-capsule width, ocellus spacing, and pronotum width. Based on the results of a frequency distribution method and Dyar’s rule, the larvae of E. brandti were divided into seven instars. Of the five variables measured, the width of the head capsule provided the best measurement for determining instar stage. The regression equation between the head-capsule widths and the instar number was y?=?0.324e^0.096x (R²?=?0.970).     

Assessment of a silhouette trap for sampling zoophilic blackflies (Diptera: Simuliidae)

A collapsible animal-type silhouette trap was designed to catch zoophilic female blackflies (Diptera: Simuliidae) which feed on the head or ventral surface of cattle. The trap was assessed for its ability to sample attacking blackflies by comparison with simultaneous manual catches from a bait cow, in an enzootic bovine onchocerciasis area in North Wales. In thirteen 1-hour collections, the trap provided a representative sample of the blackfly population in terms of the relative abundance of species. There was a strong correlation between the catch sizes from both methods (r = +0.73), and the body site feeding preferences for all species were similar with both trap and cow. There was no significant difference between the Onchocerca spp. infection rates of flies caught by either method.     

Morphological diversity of first instar larvae in Miltogramma subgenus Pediasiomyia (Diptera: Sarcophagidae, Miltogramminae)

The morphology of first instar larvae of three species of Miltogramma Meigen subgenus Pediasiomyia Rohdendorf is described using SEM and light microscope techniques. Miltogramma chrysochlamys (Rohdendorf), Miltogramma margiana (Rohdendorf) and Miltogramma przhevalskyi (Rohdendorf) share with other satellite flies the presence of an elongated sensillum basiconicum of the maxillary palpus and numerous longitudinal cuticular ridges on the integument of all segments; and they share with other Miltogramma spp. a maxillary palpus situated on a more or less raised base. While the first instar M. margiana is very similar to first instars of Miltogramma (sensu stricto), first instars of M. chrysochlamys and M. przhevalskyi share several features unique among Miltogramminae: antennal dome situated on a flat or indistinct basal ring, antennal dome flattened, border between pseudocephalon and first thoracic segment with a pair of fleshy processes, and basal ring with trichoid sensillum. First instars of M. chrysochlamys and M. przhevalskyi are unique in having both sb1 and sb2 of the sensilla basiconica of the maxillary palpus elongated, and M. przhevalskyi has an unpaired, median proleg on most abdominal segments.     

First report of a trichomycete fungus (Zygomycota: Trichomycetes) inhabiting larvae of Simulium ochraceum sensu lato Walker (Diptera: Simuliidae) from the Galapagos Islands

A collection of the larval black fly Simulium ochraceum sensu lato Walker was made at six lotic habitats on San Cristobal Island, Galapagos Islands, Ecuador, during May 2003. Sixty-eight larvae were assayed for the presence of gut fungi (Zygomycota: Trichomycetes). A trichomycete, designated as Smittium sp. was found inhabiting the hindgut of 17.6% of S. ochraceum s.l. larvae. Implications of this finding with respect to both host and trichomycete biogeography are discussed.     

Field experiments on a new method for determining age in tsetse flies (Diptera: Glossinidae)

ABSTRACT.

• 1 Data are presented which suggests that the accurate determination of the age of tsetse flies (Glossina morsitans morsitans Westwood and G. pallidipes Austen) in the field can be achieved by measuring the fluorescence content of the head capsule.
• 2 The way in which this can be achieved and further work which would improve the accuracy of the technique are discussed.

     

A behavioral method for separation of house fly (Diptera: Muscidae) larvae from processed pig manure

A behavioral method applicable in biodegradation facilities for separation of house fly (Musca domestica L.) larvae from processed pig manure is presented. The method is based on placing a cover over the larval rearing tray, while escaping larvae are collected in collection trays. Separation units must be placed in a dark room to avoid negative phototactic responses of the larvae. After 24 h of separation, over 70% of the larvae escaped from processed manure and were collected in collection trays. Most of the larvae pupated within 48 h after separation. Mean weight of pupae recovered from manure residue was not significantly different from mean weight of pupae of separated individuals. Eclosion rate of pupae recovered from manure residue was significantly lower than eclosion of separated individuals, and was strongly related to separation success. Factors responsible for escape behavior of larvae are discussed.     

DNA probes for the identification of members of the Simulium damnosum complex (Diptera: Simuliidae)

Genomic libraries in plasmid have been constructed from various sibling species of blackflies of the Simulium damnosum complex from West Africa. Three cloned repetitive sequences, which show variation in copy number between sibling species, have been isolated. These clones can be used as probes for the dot-blot identification of larvae, pupae or adults into the three main West African subcomplexes, i.e. damnosum, squamosum and sanctipauli subcomplexes. The sequences also show some intraspecific variation in copy number.     

Temporal changes in the level of infestation of Simulium ornatum Meigen (complex) (Simuliidae: Diptera) larvae by the endosymbiotic fungus Harpella melusinae Lichtwardt (Harpellales: Trichomycetes)

The fungus Harpella melusinae (Harpellales: Trichomycetes) is obligately associated with the midguts of larval Simuliidae (Diptera). The level of infestation of a population of Simulium ornatum by H. melusinae was monitored at a stream in Hampshire, England. Significant temporal changes in the level of infestation were recorded during monthly and weekly collections; a twenty-fold increase being recorded over a nine-day period. Possible mechanisms by which these changes occur are discussed.     

Why the simple frequency and Janetschek methods are unreliable for determining instars of mayflies: An analysis of the number of Nymphal instars of stenonema modestum (banks) (ephemeroptera: Heptageniidae) in virginia,USA

The Janetschek method is a variation of the simple frequency method and therefore subject to the same limitations. Instars can only be reliably determined by these methods if development within the population is known to be homogeneous. The number of nymphal instars proposed by Kondratieff and Voshell (1980) for an overwintering population of Stenonema modestum in the North Anna River of Virginia is not substantiated. These authors estimated a total of 14–15 nymphal instars using the simple frequency and Janetschek methods. A reexamination of their paper indicates that the development of this 5. modestum population is quite variable and therefore not amenable to successful instar determination using the simple frequency, Janetschek or any other indirect instar determination method. Indirect instar determination methods cannot be considered reliable in determining the number of instars of Ephemeroptera because of the developmental variability characteristic of most, if not all, mayfly species.     

An adaptive neuro-fuzzy method (<Emphasis Type="Italic">ANFIS</Emphasis>) for estimating single-trial movement-related potentials

This study aims to recover transient, trial-varying evoked potentials (EPs), in particular the movement-related potentials (MRPs), embedded within the background cerebral activity at very low signal-to-noise ratios (SNRs). A new adaptive neuro-fuzzy technique will attempt to estimate movement-related potentials within multi-channel EEG recordings, enabling this method to completely adapt to each input sweep without system training procedures. We assume that one of the sensors is corrupted by noise deriving from other sensors via an unknown function that will be estimated. We will approach this problem by: (1) spatially decorrelating the sensors in the preprocessing phase, (2) choosing the most informative of the filtered channels that will permit the best MRP estimation (input-selection phase) and (3) training the neuro-fuzzy model to fit the noise over the chosen sensor and therefore estimating the buried MRP. We tested this framework with simulations to validate the analytical results before applying them to the real biological data. Whenever it is applied to biological data, this method improves the SNR by more than 12dB, even to very low SNRs. The processing method proposed here is likely to complement other estimation techniques and can be useful to process, enhance and analyse single-trial MRPs.