Human landing catch (HLC) is the most efficient method for Aedes monitoring, but it is not ethical due to its high risk of human exposure to pathogens. We designed trials to assess the performance of an alternative human-baited double net trap (HDN) for field Aedes albopictus monitoring compared with the standard HLC. Outdoor HDN and HLC catches were conducted simultaneously at 15 field sites on two sunny days in mid-July and August. The tests were performed 3 h apart: an early morning period (7:30–8:30 h), a pre-sunset period (16:30–17:30 h) and a post-sunset period (18:30–19:30 h). A total of 90 comparisons were made between the two methods. Field comparisons were designed to minimize half-hour bias and human-bait attraction bias. Two mosquito species were collected by HDN and HLC, with the predominated species being Ae. albopictus (HDN: n = 1325, 97.35% of total; HLC: n = 531, 92.51% of total). A small proportion were adults of the Culex pipiens complex (HDN: n = 36, 2.65% of total; HLC: n = 43, 7.49% of total). Although the mean Ae. albopictus catch per hour of HLC was significantly higher than HDN (14.72 vs 5.90 per h, t(178) = 3.151, P = 0.003), there were significant positive spatial and temporal correlations between HLC and HDN for Ae. albopictus sampling among different sites and hours (r(90) = 0.785, P < 0.001; r(90) = 0.785, P < 0.001). Both methods proved that Ae. albopictus was most active during the hours before sunset and least active after sunset. No significant variation was observed in Ae. albopictus catch size of HDN between groups of more attractive and less attractive humans (3.38 vs 2.51 per 30 min, t(88) = 1.283, P = 0.201). With moderate sampling efficiency, significantly positive spatial correlation with HLC, and less human-bait attraction bias, HDN appears to be a safer alternative to HLC for Ae. albopictus monitoring in Shanghai. With mosquito activity peaking in the pre-sunset hours, Ae. albopictus catches of HDN should be performed in the hours before dark. The trap design could be improved to make it more portable and easier for field operation.

Background: Culex pipiens molestus was first reported in Shanghai in 2010. The population structures and seasonal distributions of Culex pipiens subspecies C. p. molestus, Culex pipiens pallens, and Culex pipiens quinquefasciatus are not well known. Methods: From late February to November 2013, we conducted daily field surveillance of mosquitoes at eight sites at two green lands and three residential areas in downtown Shanghai. Morphological comparison and DV/D ratios (DV/D is an indicator of mosquito taxonomy) were used to identify adult mosquitoes. Results: The distribution curves of the Culex pipiens complex members indicated seasonal fluctuations. The temperature range of 20–25 °C was the most suitable for adult activity. Micro-environmental factors may differentiate the complex population structures. Hybridization between C. p. pallens and C. p. quinquefasciatus was common and neither “DV/D = 0.40” nor “DV/D = 0.50” can distinguish these subspecies and their hybrids. Conclusion: the population structure of the Culex pipiens complex is complex and characterized by significant hybridization. Measures other than DV/D ratios are needed for the discrimination of subspecies. The C. p. molestus invasion might result in the transmission of novel vector-borne diseases in Shanghai.

The near-surface urban drainage system in Shanghai is highly complex, with hundreds of thousands of catch basins (CBs) and manhole chambers (MCs). Comparatively little is known about the breeding of mosquitoes in this vast system, especially for the locally predominant species Aedes albopictus. A cross-sectional mosquito sampling study was conducted from late July to early August of 2017 using 539 CBs and 309 MCs located in 10 communities of downtown Shanghai. We measured the water-holding status of the drainage systems and density of mosquito larvae. Mosquito species were examined on site and in the laboratory later. The CBs were characterized by a lower percentage of standing water compared to MCs (47.0% vs. 79.9%, respectively; X² = 76.407, P<0.001), but CBs contained a higher percentage of stagnant water percent than MCs (45.2% vs. 35.3%, respectively; X² = 11.465, P = 0.001). There were exclusively two species of mosquito larvae found in the drainage systems, Ae. albopictus and Culex pipiens complex. Compared with MCs, the structures of CBs were more conducive to larval production and yielded more larvae-positive samples (43.4% vs 14.2%, X² = 53.136, P<0.001) and higher larval density (8.23 vs. 4.09 per dipper, t = 3.287, P = 0.001). Aedes albopictus was the predominant species in CBs, with a constituent ratio of 71.7%. Regarding structures with different features in different locations, CBs that had a vertical grate with an unsealed lid and MCs with plastic composite covers were the most favorable types for mosquito breeding, and residential neighborhoods yielded the highest number of Ae. albopictus. Aedes albopictus was the predominant species in both CBs and stormwater MCs, especially in residential neighborhoods. CBs, particularly those with vertical grates, were a major source of mosquito production in downtown Shanghai. MCs featured more running water and fewer larvae by percentage, and few larvae were found in Sewage MCs. However, due to the tremendous baseline amount, MCs were still an important breeding source of mosquitoes. We suggest that Aedes control in Shanghai should focus on CBs or other potential larvae habitats in and around residential neighborhoods. The use of permeable materials and completely sealed covers should be adopted in the construction of CBs and MCs henceforth.

Culex pipiens molestus Forskål is common in subterranean and aboveground environments in Shanghai, China. However, little is known about its autogeny, fecundity, and other life history traits. In this study, Cx. p. molestus larvae were collected from four different types of underground parking lots and artificially maintained, without blood feeding, in a laboratory. Life history traits parameters were recorded from the F0 to F9 generation. Culex pipiens molestus from Shanghai can autogenously persist for at least 10 generations, and some females can develop more than one egg batch without blood feeding (oviposition rate in Lot C was >100% in some generations). The average number of eggs per raft produced autogenously ranged from 36.94 to 42.19. The average generation time (GT) ranged from 20.06 to 21.30 d, and the pre-oviposition time (POT) ranged from 2.17 to 12.68 d among the generations. Culex pipiens molestus from the four groups had different autogeny, fecundity, and longevity patterns. This variability may result from genetic polymorphism caused by co-occurrence with other Culex pipiens subspecies (Diptera: Culicidae).

Background: Shanghai has numerous high-rise apartment and office buildings, but the effects of these high-rise spaces on the vertical dispersal, oviposition and blood feeding behavior of Aedes albopictus are unknown. Methods: In six multi-story building blocks in downtown Shanghai, 174 mosq-ovitraps (MOT) were placed both indoors and outdoors for Ae. albopictus collection at different vertical heights from the 1st to 6th floors and a terrace on the 8th floor. Collections were made for 4 months. The human landing catch (HLC) method for Ae. albopictus monitoring was also conducted on 6 consecutive days on six floors of two of the six buildings to study the feeding behavior of Ae. albopictus at different heights. Results: Both MOTs and HLCs collected Ae. albopictus at all monitored heights. The vertical distribution, oviposition pattern and biting behavior varied significantly among the seven heights (1st–6th floors and 8th floor) (mosq-ovitrap index (MOI): X² = 140.616, df = 6, P < 0.001; HLC: F _{(5, 138)} = 15.111, P < 0.001). The MOI at low heights (1st + 2nd floors) was significantly higher than that at medium (3rd + 4th floor, P < 0.001) and high heights (5th + 6th floors, P < 0.001), and there was no significant difference in the MOI for the 3rd–6th floors. The outdoor MOIs were significantly higher than indoor MOIs at all heights (outdoor 23.09% vs. indoor 9.58%, X² = 74.121, df = 1, P < 0.001). Aedes albopictus HLC density on the ground floor was significantly higher than that on all other heights (5.04 vs. 0.13, 0.29, 0.58, 0.79 and 1.50 per half hour, P < 0.05), while no difference was detected among the heights above the ground floor (P > 0.05). Conclusions: Aedes albopictus is more common near the ground level, but it can easily disperse to higher floors in the multi-story buildings of urban Shanghai. No significant differences in Ae. albopictus density were detected within the 3rd–6th floors using MOT or HLC. This suggests that Ae. albopictus might also disperse to areas above the 6th floor and seek hosts there. Aedes albopictus prefers to oviposit outdoors; however, Ae. albopictus was also able to inhabit, oviposit and engage in blood-feeding behavior indoors on different floors. The three-dimensional dispersal pattern of Ae. albopictus in urban areas could facilitate arbovirus transmission and increase the difficulty of dengue control. Graphical

Background: Shanghai has a large number of high-rise apartment and office buildings, but the effects of these high-rise spaces on the vertical dispersal, oviposition and blood feeding behaviour of Aedes albopictus are unknown.Methods: In six multi-storey building blocks in downtown Shanghai, 174 mosq-ovitraps (MOT) were placed both indoors and outdoors for Ae. albopictus collection at different vertical heights from the 1^st to 6^th floors. Collections were made for 4 months. Human landing catch (HLC) for Ae. albopictus monitoring was also conducted on 6 consecutive days on six floors of two buildings among those mentioned above to study the feeding behaviour of Ae. albopictus at different heights. Results: MOT and HLC collected Ae. albopictus at all monitored heights. The vertical distribution, oviposition pattern and biting behaviour varied significantly among the seven heights (1^st–6^th floor and 8^th floor) (mosq-ovitrap index (MOI): F = 5.640, P < 0.001; HLC: F = 15.111, P < 0.001). The MOI at low heights (1^st + 2^nd floors) was significantly higher than that at medium (3^rd + 4^th floor, P < 0.001) and high heights (5^th + 6^th floors, P < 0.001), and there was no significant difference in the MOI for the 3^rd–6^th floors. The outdoor MOIs were significantly higher than indoor MOIs at all heights (outdoor 23.09% vs. indoor 9.58%, t = −5.139, P < 0.001). Ae. albopictus HLC density on the ground floor was significantly higher than that on all other heights (5.04 vs. 0.13, 0.29, 0.58, 0.79 and 1.50 per half hour, P < 0.05), while no difference was detected among the heights above the ground floor (P > 0.05).Conclusions: Ae. albopictus is more common near the ground level, but it can easily disperse to higher floors in the multi-storey buildings of urban Shanghai. No significant differences in Ae. albopictus density were detected within the 3^rd–6^th floors by MOT or HLC. This suggests that Ae. albopictus might also disperse to areas higher than the 6^th floor and seek hosts there. Ae. albopictus prefers to oviposit outdoors; however, Ae. albopictus was also able to inhabit, oviposit and engage in blood feeding behaviour indoors on different floors. The three-dimensional dispersal pattern of Ae. albopictus in urban areas could facilitate arbovirus transmission and increase the difficulty of dengue control.