Koon Weng Lau

Evaluation of Insect Growth Regulators Against Field-Collected Aedes aegypti and Aedes albopictus (Diptera: Culicidae) from Malaysia

ABSTRACT Susceptibility status of Aedes aegypti (L.) and Aedes albopictus Skuse larvae obtained from 12 states in Malaysia were evaluated against five insect growth regulators (IGRs), namely, pyriproxyfen, methoprene, diflubenzuron, cyromazine, and novaluron under laboratory conditions. Field populations of Ae. aegypti exhibited moderate resistance toward methoprene and low resistance toward pyriproxyfen, with resistance ratios of 12.7 and 1.4, respectively, but susceptibility to diflubenzuron, cyromazine, and novaluron. On the other hand, field populations of Ae. albopictus exhibited low resistance against diflubenzuron and novaluron, with resistance ratio of 2.1 and 1.0, respectively, but susceptibility to other tested IGRs. Our study concluded that the tested IGRs provide promising results and can be used to control field population of Ae. aegypti and Ae. albopictus, especially cyromazine. The use of IGR should be considered as an alternative when larvae develop resistance to conventional insecticides.

The black flies (Diptera: Simuliidae) from Thua Thien Hue and Lam Dong Provinces, Vietnam

Surveys of pupae and larvae of black flies (Diptera: Simuliidae) were carried out in Thua Thien Hue Province of central Vietnam, and Lam Dong Province of southern Vietnam in 2014. A total of 26 species belonging to the genus Simulium were collected, consisting of eight known species, one newly recorded species, and 17 new species (of which three species of the subgenus Nevermannia were described in 2014). The remaining 14 new species (nine of the subgenus Gomphostilbia and five of the subgenus Simulium) are described here based on females, males, pupae and mature larvae. The total number of species of black flies in Vietnam is now 46. Keys to identify all 26 species recorded from the two provinces of Vietnam are given for females, males, pupae and mature larvae.

Biting behavior of Malaysian mosquitoes, Aedes albopictus Skuse, Armigeres kesseli Ramalingam, Culex quinquefasciatus Say, and Culex vishnui Theobald obtained from urban residential areas in Kuala Lumpur

Abstract Background: There are several species of mosquitoes that readily attack people, and some are capable of transmitting microbial organisms that cause human diseases including dengue, malaria, and Japanese encephalitis. The mosquitoes of major concern in Malaysia belong to the genera Culex, Aedes, and Armigeres. Objective: To study the host-seeking behavior of four Malaysian mosquitoes commonly found in urban residential areas in Kuala Lumpur. Methods: The host-seeking behavior of Aedes albopictus, Armigeres kesseli, Culex quinquefasciatus, and Culex vishnui was conducted in four urban residential areas in Fletcher Road, Kampung Baru, Taman Melati, and University of Malaya student hostel. The mosquito biting frequency was determined by using a bare leg catch (BLC) technique throughout the day (24 hours). The study was triplicated for each site. Results: Biting activity of Ae. albopictus in urban residential areas in Kuala Lumpur was detected throughout the day, but the biting peaked between 0600-0900 and 1500-2000, and had low biting activity from late night until the next morning (2000-0500) with biting rate ≤1 mosquito/man/hour. Biting behavior of Ar. kesseli was distinctly crepuscular, which exhibited two peaks of activity at 0600-0700 and 1900-2000, while Culex quinquefasciatus and Cx. vishnui were nocturnal feeders with multiple biting peaks throughout the night. Conclusion: This study recommends optimal time for fogging to be conducted in Malaysia and neighboring countries according to the peak biting peak obtained.

Vietnam, a Hotspot for Chromosomal Diversity and Cryptic Species in Black Flies (Diptera: Simuliidae).

The increasing attention on Vietnam as a biodiversity hotspot prompted an investigation of the potential for cryptic diversity in black flies, a group well known elsewhere for its high frequency of isomorphic species. We analyzed the banding structure of the larval polytene chromosomes in the Simulium tuberosum species group to probe for diversity beyond the morphological level. Among 272 larvae, 88 different chromosomal rearrangements, primarily paracentric inversions, were discovered in addition to 25 already known in the basic sequences of the group in Asia. Chromosomal diversity in Vietnam far exceeds that known for the group in Thailand, with only about 5% of the rearrangements shared between the two countries. Fifteen cytoforms and nine morphoforms were revealed among six nominal species in Vietnam. Chromosomal evidence, combined with available molecular and morphological evidence, conservatively suggests that at least five of the cytoforms are valid species, two of which require formal names. The total chromosomal rearrangements and species (15) now known from the group in Vietnam far exceed those of any other area of comparable size in the world, supporting the country’s status as a biodiversity hotspot. Phylogenetic inference based on uniquely shared, derived chromosomal rearrangements supports the clustering of cytoforms into two primary lineages, the Simulium tani complex and the Southeast Asian Simulium tuberosum subgroup. Some of these taxa could be threatened by habitat destruction, given their restricted geographical distributions and the expanding human population of Vietnam.

First Report on Adulticide Susceptibility Status of Aedes albopictus, Culex quinquefasciatus, and Culex vishnui from a Pig Farm in Tanjung Sepat, Selangor, Malaysia

Abstract The present study aims to investigate the susceptibility status of Aedes albopictus, Culex quinquefasciatus, and Cx. vishnui collected from a pig farm in Tanjung Sepat, Selangor, toward 11 insecticides representing the classes of organochlorines, carbamates, organophosphates, and pyrethroids. The results of a World Health Organization adult mosquito bioassay revealed that Ae. albopictus, Cx. quinquefasciatus, and Cx. vishnui exhibited different susceptibility toward various insecticides. Overall, pyrethroids were able to induce rapid knockdown for all test mosquito species. The pyrethroids lambdacyhalothrin and etofenprox were able to cause high mortality (>80%) of all 3 species. The findings of the present study will benefit local authorities in selecting appropriate dosage of insecticides to be used in mosquito control in this area.

Comparative Efficacy of Commercial Mosquito Coils Against Aedes aegypti (Diptera: Culicidae) in Malaysia: A Nationwide Report

Abstract This study was conducted using the glass chamber method to determine the susceptibility status of the dengue vector, Aedes aegypti (L.) from 11 states in Malaysia to commercial mosquito coils containing four different active ingredients, namely metofluthrin, d-allethrin, d-trans allethrin, and prallethrin. Aedes aegypti exhibited various knockdown rates, ranging from 14.44% to 100.00%, 0.00% to 61.67%, 0.00% to 90.00%, and 0.00% to 13.33% for metofluthrin, d-allethrin, d-trans allethrin, and prallethrin, respectively. Overall, mortality rates ranging from 0.00% to 78.33% were also observed among all populations. Additionally, significant associations were detected between the knockdown rates of metofluthrin and d-allethrin, and between metofluthrin and d-trans allethrin, suggesting the occurrence of cross-resistance within pyrethroid insecticides. Overall, this study revealed low insecticidal activity of mosquito coils against Ae. aegypti populations in Malaysia, and consequently may provide minimal personal protection against mosquito bites.

Dimorphic male scutal patterns and upper-eye facets of Simulium mirum n. sp. (Diptera: Simuliidae) from Malaysia.

BackgroundA species of Simulium in the Simulium melanopus species-group of the subgenus Simulium (formerly misidentified as S. laterale Edwards from Sabah and Sarawak, Malaysia) is suspected to have dimorphic male scutal color patterns linked with different numbers of upper-eye facets. This study aimed to confirm whether or not these two forms of adult males represent a single species.MethodsDNA sequences generated from four genetic loci, the mitochondrial-encoded COI, COII, 12S rRNA and 16S rRNA genes, of both forms of Simulium sp. males were compared with each other and also with those of the females and larvae of the same species. Four other related Simulium spp. were also used for comparison.ResultsBoth the concatenated dataset and single-locus phylogenetic analyses indicate that the two distinct morphological males of Simulium sp. are indeed conspecific, and represent, together with their associated females and larvae, a distinct species.ConclusionsBased on DNA analyses, Simulium sp. is proven to show dimorphism in males and is herein described as a new species, Simulium mirum Takaoka, Sofian-Azirun & Low. This is the first report of such a novel species among the family Simuliidae.

Three new species of Simulium ( Nevermannia ) (Diptera: Simuliidae) from Vietnam

Three new species of black flies, Simulium (Nevermannia) langbiangense, S. (N.) phami, and S. (N.) bachmaense, are described on the basis of females, males, pupae and larvae collected in Vietnam. All three species are assigned to the Simulium feuerborni species-group of Simulium (Nevermannia). Simulium (N.) langbiangense sp. nov. is characterized by the female sensory vesicle with a large opening, and a short common basal stalk of the six pupal gill filaments, S. (N.) phami sp. nov. is most striking in having the pupal gill with five filaments, a character not reported in species of the S. feuerborni species-group, and S. (N.) bachmaense sp. nov. is characterized by the female genital fork with a triangular lobe-like projection pointed posteromedially on each arm, and the small larval postgenal cleft. This represents the first record of the S. feuerborni species-group from Vietnam.

Two New Species of Simulium (Gomphostilbia) (Diptera: Simuliidae) From Flores, Indonesia

Abstract Two new species, Simulium (Gomphostilbia) sunapii and S. (G.) rangatense, are described based on adults, pupae, and mature larvae from Flores, in the eastern part of the Sunda Archipelago, Indonesia. Simulium (G.) sunapii sp. nov. is placed in the S. asakoae species-group, representing the easternmost geographical record for the group in this archipelago. It is characterized by a small number of male upper-eye large facets in eight or nine vertical columns and 12 horizontal rows. Simulium (G.) rangatense sp. nov. is placed in the S. ceylonicum species-group and is characterized by the pupal gill with six filaments. This new species, together with two related species of the S. ceylonicum species-group in Flores, suggests the species radiation of this speciesgroup might have been accompanied by a reduction of the number of pupal gill filaments from eight to four through six. Taxonomic notes are provided to distinguish these two new species from related species.

Simulium ( Gomphostilbia ) lemborense , a new black fly species (Diptera: Simuliidae) from Flores, Indonesia

Simulium (Gomphostilbia) lemborense sp. nov. is described based on adults, pupae and mature larvae from Flores, in the eastern part of the Sunda Archipelago, Indonesia. This new species is placed in the Simulium batoense species-group of the subgenus Gomphostilbia Enderlein, representing the most eastern distribution record for the group. This new species is characterized by a narrow female frons and pupal gill with eight filaments, of which two filaments of the ventral pair are three to four times as long as the six other filaments. Taxonomic notes are provided to distinguish this new species from related species.