Lethality and repellency of emulsifiable concentrates (EC) or microencapsulated concentrates (MC) of fenitrothion, diazinon, propetamphos and chlorpyrifos-methyl were examined with 12 separate colonies of the German cockroach, Blattella germanica. Field colony individuals were collected from 5 different restaurants situated on the 7th floor of a building in Koto-ku, and 7 restaurants located on the 5th floor of another building in Meguro-ku, Tokyo, Japan. Adult male progeny of each colony were released into a container with insecticide-treated harborage surfaces. All colonies, except for the one from the Italian restaurant in Koto-ku, showed low levels of susceptibility to fenitrothion EC and MC, diazinon EC and MC, chlorpyrifos-methyl EC and propetamphos EC. However, the levels of lethality against colonies varied even though they originated from the same floor of a building. The poor efficacy of the test insecticides was probably a result of long-term use of these compounds in this area of building. Various susceptibilities among colonies indicate that the German cockroach does not frequently hybridize between restaurants even located on the same floor of a building. Propetamphos MC was the most effective against all exposed colonies, followed by fenitrothion MC and diazinon MC. Changes in behavior toward insecticides and insecticide resistance in the EC formulations may cause low mortalities in cockroaches. The test colonies showed two different types of low susceptibilities, one due to high aversion to the test formulations and another due to insecticide resistance.

View full abstract

Insects are potential mechanical vectors and carriers of pathogenic microorganisms. True fungi (Eumycota), associated with insects, may be harmful to humans as an allergen and cause contamination in the food industry. A total of 47 dead or live insects comprising 21 different families were collected from 4 study sites (baking factory, rice cracker factory, rice processing factory and central kitchen) in Aichi Prefecture, Japan. True fungi isolated from the body surface of household or industrial insects were evaluated. In this study, 10 genera of true fungi (Cladosporium spp., Penicillium spp., Alternaria spp., Aureobasidium spp., Rhizopus sp., Aspergillus spp., Nigrospora sp., Phoma sp., Curvularia sp. and Fusarium sp.) were isolated from 35 (74.5%) of 47 collected specimens. These isolated true fungi are common in human environments. Among the 10 genera of true fungi, Cladosporium spp. were most frequently found in the study sites. There was almost no correlation between insect body sizes and colony forming units (CFU) (Spearman r_s=0.195, p=0.189). Dead and live insects may provide an ideal environment for the growth of true fungi in food manufacturing environments. Therefore, good sanitary practices should be implemented to eliminate industrial and household insect pests.

View full abstract

Simulium (Simulium) thongsahuani sp. nov. is described on the basis of pharate females, pharate males, pupae and mature larvae collected in Songkhla Province in southern Thailand. This new species is assigned to the griseifrons species-group of the subgenus Simulium (Simulium), and is easily distinguished from other known species of this species-group by the combination of the simple wall-pocket shaped cocoon and the six pupal gill filaments of which the lower three filaments are subequal in thickness to one another and much thinner than the others.

View full abstract

A redescription of adults and previously undescribed pupae and larvae of Topomyia auriceps Brug, 1939 are made, and a closely related new species Topomyia pseudoauriceps is described from Sarawak Malaysia. The male genital organs of the two species are illustrated and compared. These larvae are predacious with well developed maxillae and they breed in the leaf axils of various kinds of wild plants such as taro and wild banana.

View full abstract

The female of Simulium (Gomphostilbia) kuvangkadilokae Pramual and Tangkawanit, 2008 is described for the first time on the basis of specimens collected at Tad Yai Waterfall (the type locality) in Amnat Charoen Province and at Huai Yang, Ubon Ratchathani Province, Thailand. The male, pupa and larva of this species are also redescribed.

View full abstract

A new species of black fly, Simulium vanellum, is described and illustrated from the female, male, pupa, and larva collected in Thong Pha Phum District of Kanchanaburi Province, Thailand. It is morphologically most similar to Simulium indicum and Simulium nigrogilvum, and is tentatively placed in the Simulium griseifrons species group.

View full abstract

The male, pupa and larva of Simulium (Gomphostilbia) novemarticulatum Takaoka and Davies, 1995 are described morphologically on the basis of specimens collected from Peninsular Malaysia (type country) and southern Thailand. This species is very similar to S. (G.) charlesi Takaoka, 2008 from Sarawak but readily distinguished in the male by the slender style, in the pupa by the ventral paired filaments of the gill of almost the same size, and in the larva by the bifid dark thick setae on the dorsal and dorsolateral surfaces of abdominal segments 5-8. The difference between S. (G.) novemarticulatum and S. (G.) charlesi, as well as the identification of Thai specimens as S. (G.) novemarticulatum, is confirmed molecularly.

View full abstract

Prediapause migration of Culex tritaeniorhynchus reported one year previously was observed again in the autumn of 2008 in the same park in urban Tokyo. The time course of prediapause migration in 2007 and 2008 was similar starting in mid-/late September, peaking in mid-October and ending in December. The density of Cx. tritaeniorhynchus that migrated was higher in 2008 than 2007 throughout the study period with a peak density of 3,740 per 1 hr of sweeping, 3.5 times higher than in 2007. A total of 16,892 and 29,188 Cx. tritaeniorhynchus resting on vegetation were collected by sweeping from April to December in 2007 and 2008, respectively, with 99.9% collected during September to December in both years. Dissection showed that 96.5% (222/230) of these females in 2008 were in reproductive diapause with an ovariole stage of N or I and a primary to secondary follicular ratio of ≤1.5. In addition to Cx. tritaeniorhynchus, 11 mosquito species were collected in this study from September to December and 6 species were breeding in the park. The remaining 3 species were rice field mosquitoes and appeared in the autumn, coinciding with the appearance of Cx. tritaeniorhynchus. Mosquito collections were made in 2 additional study sites in mid-October 2008 to check for the occurrence and density of Cx. tritaeniorhynchus, and the average density of Cx. tritaeniorhynchus was significantly different between study sites. Hourly changes in direction and velocity of the wind during September to October indicated that a large part of the migrating Cx. tritaeniorhynchus originated from north to north-northwest areas of the study park. A total of 211 overwintered Cx. tritaeniorhynchus females including 4 blood-fed females were collected at the study site during March to early May 2009, indicating the presence of hibernacula for Cx. tritaeniorhynchus near the study site. Blood-meal identification by PCR using primers based on the cytochrome b gene and the 16S-rDNA region of vertebrate hosts showed that two blood meals were human-derived, one was cat-derived and the remaining meal showed no amplification.

View full abstract

In the spring and autumn of 2007 and 2008, wild rodents were captured in five regions of Yamagata Prefecture where cases of tsutsugamushi disease have been reported. Attached trombiculid larvae were collected from the captured rodents. In the spring, 7,695 trombiculid larvae were collected from 65 wild rodents and classified into 9 species in 3 genera. Numerous cases of tsutsugamushi disease have been reported in areas where Leptotrombidium pallidum is the major species among collected larvae, so this high incidence is likely attributable to a substantial distribution of L. pallidum. In autumn, 8,498 trombiculid larvae were collected from 112 wild rodents and classified into 11 species in 3 genera. Leptotrombidium scutellare not observed in these areas since the 1980's, was collected from Sakegawa-Village and Tozawa-Village. Moreover, the Orientia tsutsugamushi gene of the Kawasaki type was detected by nested PCR from the spleen of two wild rodents captured in the autumn from Sakegawa-Village. Kawasaki type-tsutsugamushi disease, recognized as rare in the Tohoku-district, may be endemic to some parts of Yamagata Prefecture.

View full abstract

To estimate the vector species of arboviruses affecting cattle, Culicoides biting midges were collected by light traps in Naha and Ishigaki cities in Okinawa from 2001-2004. Four and 14 Culicoides species were captured in Naha and Ishigaki cities, respectively. One strain of Bluetongue virus (BTV) was isolated from Culicoides brevitarsis Kieffer collected in Naha city on December 2003. Genetic and phylogenetic analyses showed that the strain was closely related to the Australian and Asian BTV isolates. Our data indicate that C. brevitarsis is likely to be a vector species of BTV in Okinawa.

View full abstract