The presence of predators can have dramatic consequences on prey communities, not only by the direct effects of consumption but also through sublethal effects. We investigated the survival rate and subsequent life history of the mosquito Culex pervigilans Bergroth under the influence of its major predator, the backswimmer Anisops wakefieldi White. We established a field experiment with various treatments: 1) control without predators, 2) free-roaming A. wakefieldi (with one, three, or nine A. wakefieldi per container), 3) caged A. wakefieldi (empty cage without predators, with one, three, or nine A. wakefieldi in each cage, and 4) A. wakefieldi cues (with cues concentrations of one, three, or nine A. wakefieldi). Cx. pervigilans eggs were then taken from these four experimental treatments and reared in two different laboratory conditions: 1) in clean water without any traces of predators, or 2) in water with the same treatments as in field. The survival rate of Cx. pervigilans was significantly reduced by the presence of predators or their cues. Even after a brief exposure to waters containing predators or residual cues, the subsequent progeny and the ontogeny of the remaining survivors were still affected. The percentage of eggs that hatched, and the resulting mosquito population, was influenced by the presence of predators or their cues. Our results suggest that sublethal effects may be carried by surviving individuals primarily through the effects of stress, perhaps by epigenetic mechanisms. We may expect to observe similar plasticity in species or populations with high temporal or spatial variability in predation.
Maxillae and mandibles of males of 44 species of 12 mosquito genera and females of three autogenous genera and two partially autogenous species were examined under light microscopy and scanning electron microscopy. The maxillae and mandibles of male mosquitoes are delicate, tape-like structures with lengths characterizing genera or higher level classification units. Five patterns are recognized: (A) long maxillae and mandibles with mandibles longer than maxillae in Anopheles; (B) long maxillae and mandibles with maxillae longer than mandibles in Toxorhynchites; (C) short or intermediate lengths of maxillae with short mandibles in Aedes, Armigeres, Culex, Ochlerotatus, Orthopodomyia, and Uranotaenia; (D) short or intermediate length of maxillae with no mandibles in Mimomyia and Tripteroides; and (E) no maxillae and mandibles in Malaya and Topomyia. Maxillary and mandibular lengths of male mosquitoes show a positive correlation. Length of maxillae and mandibles of autogenous females are reduced to the same level as conspecific males. In contrast, females of partially autogenous species have complete maxillae and mandibles as in females of anautogenous species.
A 2-yr study of Japanese encephalitis (JE) virus in Sepang District, Selangor, Malaysia, was carried out to identify the mosquito vectors and to determine their seasonal abundance, parity, and infection rates. In total, 81,889 mosquitoes belonging to 9 genera and > 50 species were identified from CDC trap collections augmented with dry ice during 1992 and 1993. Culex tritaeniorhynchus Giles and Culex gelidus Giles were the most abundant species, and both increased in numbers with increases in rainfall. Overall, 45 JE virus isolations were made from 7 species-Cx. tritaeniorhynchus (24), Cx. gelidus (12), Culex fuscocephala Theobald (2), Aedes butleri Theobald (4), Culex quinquefasciatus Say (1), Aedes lineatopennis Ludlow (1), and Aedes (Cancraedes) sp. (1). Based on elevated abundance and JE infection rates, Cx. tritaeniorhynchus appears to be the most important vector of JE virus in Sepang.
The population size, age-class structure, and movement of the American cockroach, Periplaneta americana (L.) (Dictyoptera: Blattidae), were studied in three sewers in Penang, Malaysia, from September 2008 to October 2009. Eighteen to 20 glass-jar traps (two per manhole) were deployed for a 24-h period during each sampling occasion at each sewer. Adults and nymphs were active throughout the study period, with an average monthly trap catch of 57-97 adults and 79-99 nymphs. The mean proportions of adults and nymphs at the three sewers ranged from 0.47 to 0.57. Of the 2177 male and 2717 female cockroaches marked and released over the three sewers, recapture rates were 29.4-45.8 and 30.8-47.0%, respectively. The proportion of marked males and females did not differ significantly from the proportion of recaptured marked males and females. However, the mean number of times a marked female was recaptured was significantly greater than that of males. Of the 783 males and 1,030 females that were marked and recaptured, 19.4 and 24.7%, respectively, had moved between manholes, and significantly more females than males moved between manholes. Of the 406 recaptured marked adults that moved between manholes, 90.4% moved a distance of 2-20 m from their initial release site; one male moved 192 m, the longest distance recorded. Trap catch on each sampling occasion was positively correlated with daily mean temperature. The number of cockroach movements between manholes also was correlated with the mean daily minimum temperature.
Factors affecting the mechanical transmission of rotavirus by the legs and wings of the housefly, Musca domestica L., were examined in a laboratory study. Rotavirus was picked up when houseflies walked on thin smears of clarified rotavirus suspensions. The addition of glycerol, which increased viscosity of the virus suspension, and particulate human feces slightly increased the proportion of flies contaminated with virus. However, the addition of glycerol greatly reduced the average number of virus particles picked up per fly, whereas feces greatly increased the number of particles. The proportion of flies with virus-contaminated legs, which transferred virus to > 1 contact surface, was increased by longer contact time with the surface and when the contact surface was agar instead of glass. Most virus particles were deposited on 1st contact with the surface. Most flies dislodged virus particles inoculated on the underside of their wings soon after the start of simulated flight. Our data indicated that the nature of the virus-suspending medium has a greater effect on the level of virus contamination than on the ability to become contaminated. The importance of walking as a mode of virus transport depends on the nature of the contact surface, the risk of the contaminated fly settling first on a surface likely to come into contact with humans, and fly numbers.
Simulium (Gomphostilbia) leparense sp. nov. is described from females, males, and pupae collected from Peninsular Malaysia. This new species is assigned to the ceylonicum species-group of the subgenus Gomphostilbia, and is characterized by the female and male scuta covered with dark-brown short hairs, smaller number of male upper-eye facets, presence of shiny paired spots on the male abdominal segments 2-8, and absence of grapnel-shaped hooklets on the pupal abdominal segment 9. The male and pupa of S. capillatum Takaoka, which was originally described from larvae collected from Sarawak and Sabah, are described for the first time. Keys to identify all 32 species of the Simulium ceylonicum species-group including 27 species from other countries are provided for females, males, pupae, and mature larvae.
Two new blackfly species, Simulium (Gomphostilbia) azhari and Simulium (Gomphostilbia) johorense, are described based on adult females, males, pupae, and larvae collected from Peninsular Malaysia, and assigned to the parahiyangum subgroup and the duolongum subgroup of the batoense species group of the subgenus Comphostilbia, respectively. S. (G.) azhari sp. nov. is characterized in the female by the narrow frons, and in the male by the broad style and the ventral plate moderately produced ventrally. S. (G.) johorense sp. nov. is also remarkable in having the female subcosta lacking hairs or bearing a reduced number of hairs ranging from one to five. The pupae of both new species share a similar arrangement of the eight gill filaments (i.e., stalks of dorsal and middle triplets and ventral pair arising at the same level from the short common basal stalk), although relative lengths of filaments of the ventral pair to those of the dorsal and middle triplets are different between the two new species. Taxonomic notes are given to distinguish these new species from other related species. Keys to identify all 10 species of the batoense species group in Peninsular Malaysia are provided for adult females, males, pupae, and mature larvae.
Simulium (Comphostilbia) izuae sp. nov. is described from female, male, pupal, and larval specimens collected from Cameron's Highlands, Peninsular Malaysia. This new species is placed in the asakoae species-group of the subgenus Gomphostilbia. The pupa of this new species is characterized by the gill with eight long filaments arranged as (3 + 3) + 2 filaments, of which the ventral pair of filaments is borne on a stalk that is always shorter than the common basal stalk. Taxonomic notes to distinguish this new species from five other Malaysian species and 12 other species of the asakoae species-group from other countries are given. Keys to identify all 18 species of the asakoae species-group are also provided for females, males, pupae, and mature larvae.
ABSTRACT A new black fly species, Simulium (Comphostilbia) langkawiense, is described based on adult female, adult male, pupal, and larval specimens collected from Langkawi Island, Malaysia. This new species is similar in the configuration of the pupal gill to Simulium (Comphostilbia) gombakense Takaoka & Davies, 1995, originally described from Peninsular Malaysia, but differs from the latter species by the female genital fork with an anterolaterally angulated plate on each arm, the female tarsal claw tooth shorter than one half of the claw, the small number of male upper-eye large facets, the ventral plate with its ventral margin nearly flat in the middle when viewed posteriorly, and the inflated structure of the pupal gill with a less produced middle portion (width of middle inflated portion: length of inflated structure = 0.24). Taxonomic notes are also given to separate this new species from two other related species from Nepal and India. This represents another example of a unique species of black fly on one of the continental islands of Peninsular Malaysia.
Simulium (Asiosimulium) furvum sp. nov. (Diptera: Simuliidae) is described from female, male, pupal, and larval specimens collected from Maewa National Park, Lampang Province, Thailand. This new species represents the fourth member of the subgenus Asiosimulium Takaoka & Chochoote, one of two small black fly subgenera endemic in the Oriental Region. It is characterized by a pear-shaped spermatheca in the female; a ventral plate in the male with a laterally compressed median keel directed ventrally and with a deep notch posteromedially, and aedeagal membrane with stout spines; and by 22 gill filaments in the pupa. Taxonomic notes are provided to separate this new species from three known species, Simulium (Asiosimulium) oblongum Takaoka & Choochote and Simulium (Asiosimulium) wanchaii Takaoka & Choochote, both from Thailand, and Simulium (Asiosimulium) suchitrae Takaoka from Nepal.
Two new species of black flies, Simulium (Comphostilbia) terengganuense sp. nov. and Simulium (Gomphostilbia) aziruni sp. nov. (Diptera: Simuliidae), are described on the basis of reared adult, pupal, and larval specimens collected from Peninsular Malaysia. Both species are placed in the batoense species-group within the subgenus Gomphostilbia, one of two dominant subgenera of the genus Simulium in Peninsular Malaysia as well as in the Oriental Region. Strikingly, three morphological characteristics that rarely occur in the subgenus Gomphostilbia are found in these two new species: the very narrow female frons and the mushroom-like pupal terminal hooks in S. (G.) terengganuense sp. nov. and the pupal gill composed of an inflated horn-like structure and eight slender filaments in S. (G.) aziruni sp. nov.
Simulium (Simulium) kisapense sp. nov. is described on the basis of reared adult, pupal, and larval specimens collected from Langkawi Island, Peninsular Malaysia, and placed in the multi-striatum species-group in the subgenus Simulium. This new species is characterized by the bare basal section of the female radial vein, the male ventral plate with setae, the eight pupal gill filaments divergent at an angle of >90 degrees, and the shoe-shaped cocoon with small lateral window(s). Taxonomic notes are given to separate this new species from S. (S.) hirtinervis Edwards and S. (S.) malayense Takaoka and Davies, both from Peninsular Malaysia, and several other known species from Bhutan, India, Nepal, and Thailand.
Simulium (Gomphostilbia) merapiense sp. nov. is described based on females, males, pupae, and mature larvae from Yagyakarta, Java, Indonesia. This new species is placed in the Simulium epistum species-group, and is characterized by the pupal gill with eight short filaments all arising at the same level from a short stalk, somewhat enlarged basal fenestra, entirely bare pupal head and thoracic integument, and small and short larval postgenal cleft. These characters rarely are found in the subgenus. Taxonomic notes are given to separate this new species from related species of the S. epistum species-group.