Laboratory and Field Performance of Five Cheap Commercial Light Traps for Capturing Mosquitoes In China

Mosquito light traps for household use are popular because they are small, cheap, user friendly, and environmentally friendly. At present, there are many variations and specications of mosquito traps intended for household use on the market. Their labels claim they are powerful, but research and evaluation of their claims is lacking. Methods This article tested the key parameters, the laboratory capture rates, and the eld capture rate of 5 popular mosquito traps intended for household use. Results The study found that in the laboratory experiment, the capture rate of the mosquito traps selected was between 34.7%-65.0%. The analysis showed that the fan speed, and design of the air guide of the traps are important factors that affect the mosquito catch rate. Field tests in the greenhouse found that the 5 mosquito traps had high catch rates for Culex quinquefasciatus. The average percentage of Cx. quinquefasciatus, Aedes albopictus, Anopheles sinensis, and other ying insects captured every night was 51.76%, 25.29%, 14.12%, and 8.82%, respectively. There was no signicant difference in the capture rate of Ae. Albopictus and An. sinensis by the 5 mosquito traps in the greenhouse, but a signicant difference in the catch rate of Cx. Quinquefasciatu. ve mosquito traps. mosquito traps for household adjusting the fan speed and optimizing the air guide. to be tested was placed in the center of the test room and the light source was set 1.5 m away from the ground. Next, we released 100 mosquitoes into the test room, closed the doors and windows, and turned on the power supply to the mosquito trap, and turn off other irrelevant power sources. At 8 a.m. on the second day, we cut off the power supply and wrapped the mosquito trap in a silk yarn cage to prevent the mosquitoes from escaping. Afterward, we extracted the mosquito trap’s collection device to check the number of test mosquitoes captured to calculate the capture rate.


Introduction
Mosquito-borne diseases such as malaria, dengue fever, Chikungunya fever, and Zika infection are major threats to global health, especially dengue fever, which has increased 30-fold in the past 50 years [1,2,3,4]. Of the more than 50 known mosquito-borne diseases, vaccines are available only for epidemic encephalitis and yellow fever. The Basic way to curb other mosquito-borne diseases is mosquito control [5,6,7,8,9]. During mosquito season or a mosquito-borne disease epidemic, it is necessary not only to implement integrated mosquito control in the external environment, but also to control mosquitoes and prevent bites in residential homes.
In malaria-endemic Africa, indoor control methods for the malaria vector Anopheles mosquitoes are mainly indoor residual spraying (IRS), which usually requires implementation by professional pest control personnel [10,11,12,13,14]. Mosquito incense and aerosols are traditional mosquito control methods in the home environment in dengue-endemic Southeast Asia and southern China. Due to the social attention to environmental protection and health concern, the number of families who have begun to adopt non-chemical mosquito control methods is increasing. One of these methods is the use of a mosquito trap.
Mosquito traps intended for household use are based on light mosquito trapping techniques for mosquito surveillance, such as the ultraviolet light trap for mosquito surveillance issued by the Centers for Disease Control and Prevention (CDC) [15,16,17,18]. Mosquito traps for household use are popular because they are small, cheap, user friendly, and environmentally friendly. The design principle of this kind of product is the same as that used by professionals. The light source used is an ordinary ultraviolet light or light-emitting diode (LED). The wavelength range of the ultraviolet light is 320-400 nm, and a fan is set to form a guiding air ow, which draws the mosquitoes into the mosquito collection device, where they are trapped.
At present, there are many variations and speci cations of mosquito traps intended for household use on the market. Their labels claim they are powerful, but research and evaluation of their claims is lacking. For that reason, we selected ve popular mosquito traps costing 200 RMB ($30) or less and evaluated their mosquito control performance in the home environment. We paid attention especially to how well they were made, and their mosquito capturing performance in the laboratory and in the eld to provide valuable information for the control of mosquito-borne diseases by mosquito traps for household use.

Materials And Methods
Description of the Five Light Traps and Quality Check

Source of mosquito trap
For this study, we purchased ultraviolet mosquito traps intended for household use from a well-known eCommerce store in China (JD.com,stock code: JD). We selected ve of high sales and popular variations of mosquito traps with a price not exceeding 200 RMB ($30) for research and evaluation. The product parameters are shown in Table 1.  [19]. The appliances were supplied with rated voltage and operated under normal working conditions. The test equipment used was the PMS-80 ultraviolet (UV)-visible (VIS)-near infrared (NIR) spectroscopy analysis system, which measures radiation at 1 m. The maximum radiation should be recorded when the measuring instrument is placed.
According to the speci c operation process of the spectrometric testing instrument, the ve variations of the mosquito traps were determined in order of number, and the data obtained after the test were analyzed. The total effective radiation was calculated by the following formula. Where: E--Effective Radiation; S λ --Relative Spectral Weight Factor; When measuring spectral irradiance, the radiation required a stable light source. The effective radiation of each wavelength is calculated as the spectrum according to the ultraviolet (UV) of the spectral weight factor of different wavelengths. The total effective radiation (E) should not exceed 1 mW/m 2 .

Determination of ultraviolet mosquito trap air suction fan speed
The test was carried out following the stipulations of the Chinese National Standard A. C. Fans and Regulators [20], and the test equipment used was the Hima-split anemometer AS8336. During the test, only the anemometer can be placed in front of the outlet of the fan. In the middle of the test, the tester can stay at the inlet side. The tester is only allowed to enter the fan outlet area when they need to control the speed and read the data. The tester should take minimum time to record the data and control the fan speed. The measurement begins about 20 mm from the air outlet side. For a more accurate result, the fan is sectioned into 4 quadrants (points).
The anemometer is used to test the outgoing wind speed of each quadrant of the fan. Afterward, the value indicated by the anemometer is divided by the sampling time of the anemometer at that quadrant to measure the wind speed (m/s). The time used in measuring wind speed should not be less than 1 min. The test method followed the mosquito trap method and the human landing catch method stipulated in the China National Standard for Vector Density Monitoring Method-Mosquitoes [22]. In the mosquito trap method, we placed the mosquito traps in a sheltered area away from any interfering light source. The light source of the mosquito trap was placed 1.5m away from the ground. One hour before sunset, we turned on the mosquito traps to start the test. The power remained on until 1 hour after sunrise the next day. Repeat three times for each trap. After turning off the lamp, we wrapped the mosquito traps with a silk yarn cage to prevent the captured mosquitoes from escaping. Then we counted and categorized the number and species of female mosquitoes captured.

Species Identi cation and Statistical Analysis
Morphological identi cation of mosquitoes captured, including mosquito species and genders, was performed using an anatomical microscope and the capture performance of the ve mosquito traps was evaluated. All statistical analyses were performed using test and Pearson correlation coe cient were used to analyze the data. In terms of statistical signi cance level, * means P < 0.05, ** means P < 0.01, *** means P < 0.001.

Product Quality
The ultraviolet wavelengths of the ve mosquito traps were measured by a PMS-80 ultraviolet (UV)-visible (VIS)-near infrared (NIR) spectroscopy analysis system. The results are shown in Table 2. According to the Chinese National Standard Household and Similar Electrical Appliances-Safety-Particular Requirements for Insect Killers [19], mosquito traps exceeding 1 mW/m 2 total effective radiation exceed that which is allowed and are deemed unquali ed. Therefore, mosquito trap 5 is judged to be unquali ed, because its total effective radiation is 2.1980 mW/m 2 , which exceeds the standard allowance. Whereas the remaining 4 traps are quali ed. The fan speed test results of the suction fan of the traps are shown in Table 2. The average fan speed of mosquito trap 5 is 2.10 m/s, which is the highest among all the traps.

Laboratory Tests
The results of the mosquito capture rate test in the laboratory are shown in Table 3. The results of variance analysis and the Tukey test showed that there were signi cant differences in the trapping rate of the ve mosquito traps (P < 0.001). The capture rate of mosquito trap 5 and 1 exceeded 50%, which was signi cantly higher than that of the other three mosquito traps.

Discussion
It was reported that there was no signi cant difference in the capture e ciency of light traps among the three kinds of mosquitoes widely distributed in China, Cx. quinquefasciatus, Ae. Albopictus and An. sinensis in laboratory tests. [17] . Cx. Quinquefasciatus is stipulated as tested insects by Chinese National Standard Laboratory E cacy Test Methods and Criterion of Public Health Equipment-Electronic Trap for Mosquitoes and Flies [21] . In this study, Cx. Quinquefasciatus was also chosen to evaluate the capture e ciency of ve light traps.
The ultraviolet light of all ve household mosquito traps had a wavelength range of 390-400nm, which conformed to the standard ultraviolet light range. According to the Pearson correlation coe cient, the correlation coe cient between the ultraviolet light wavelength of the ve mosquito traps and the mosquito capture rate in the laboratory was subtle (P > 0.05). Therefore, the ultraviolet light wavelength was not a signi cant factor in uencing the difference of capture rate in the selected mosquito traps. In the study of David P Tchouassi, the attraction preferences of blue(430nm), green(570nm), red(660nm) and ultraviolet(390nm) light to mosquitoes were compared, and the results showed that blue and green light in visible light have relatively higher mosquito trapping e ciency than others [23] . B M Costa-Neta's research also supports that LED mosquito traps equipped with green(520nm) and blue(470nm) light have higher trapping e ciency [24] . However, Alongkot Ponlawat's research shows that the traps that emit ultraviolet light (10-400nm) are better than green(490-570nm) and red(620-780nm) light, which is completely opposite to the results of previous studies [25] . In the study of Emmanuel P. Mwanga, the effect of UV (364nm) LED mosquito trap is equal to or better than CDC incandescent lamp, and the indoor effect is better than outdoor [26] . The mosquito traps in this study have a relatively small range of ultraviolet light and does not involve research in the visible light band. Follow-up will expand the ultraviolet light band and select the blue and green light in the previous research conclusions for the next step.
In this study, the fan speed and laboratory capture rate exhibited a linear relationship according to Pearson correlation coe cient analysis on the air suction e ciency of the mosquito traps, which showed that fan speed might be a crucial factor in uencing the mosquito capture performance of the traps (P < 0.05). Other researchers also tested the effect of different fan speeds against the performance of the trap in capturing mosquitoes. The result showed that 1.7 m/s was the ideal suction rate to obtain a higher capture rate and lower damage to the bodies of captured mosquitoes [27] . In our study, mosquito trap 5 had the highest capture rate with an air suction rate of 2m/s. And the mosquitoes captured did not show critical damage to their bodies. Therefore, we guess that the mosquito capture performance can be enhanced by appropriately increasing the air suction rate, but whether this conclusion can be drawn remains to be further studied.
Mosquito trap 5 and trap 1 had the highest mosquito capture rates during the laboratory and eld tests. This may be due to their shape and structural design, which were different from the other three mosquito traps (Fig. 2). Trap 5 and trap 1 have inclined upward-opening entries, which means they can capture mosquitoes from 360° around the top, whereas the entries of the other three traps are located at the middle (Fig. 2B), where the air ow into the entries is parallel and thus there is a smaller capture area. The capture area might be one factor in uencing the mosquito capture rate.

National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention reported that
the mosquito species in residential areas in 2018 was mainly Cx. quinquefasciatus, accounting for 60.25% of the total [28] ; in 2019, the species of mosquitoes in residential areas were Cx. quinquefasciatus Mainly 57.73%, followed by Anopheles sinensis, Cx.
tritaeniorhynchus, and Ae. albopictus, which accounted for 20.27%, 12.22%, and 2.29%, respectively [29] . In the greenhouse experiment of this study, the 5 kinds of mosquito traps caught the most mosquito species were Cx. quinquefasciatus, accounting for 51.76%, followed by Ae. albopictus (25.29%). The capture of Cx. quinquefasciatus is roughly in line with the national survey and monitoring in the past two years. The population density of Ae. albopictus is higher than the national total, which also re ects one of the reasons for the frequent outbreaks of dengue fever in Guangxi in recent years, which may be caused by the increasing population density of Ae. albopictus.
Mosquito trap 5 and trap 1 had a relatively high capture rate of mosquitoes, which was signi cantly higher than that of the other three traps. Further, the difference was particularly signi cant in the capturing of Cx. quinquefasciatus. The total effective radiation of mosquito trap 5 exceeded the standard quite a bit, and its air suction rate was also the largest, which may be the reason for its high capture rate.
Mosquito trap 1 achieved high capture e ciency under the premise of product compliance and should be an excellent choice among the ve mosquito traps for household use that we evaluated.
There were few studies on the capture rate of mosquito traps for household use. This study tested the product parameters of ve popular mosquito traps, the capture rate in the laboratory and the capture rate in a eld test and preliminary data obtained, which provided research and development ideas for improving the performance of mosquito traps marketed for household use in China.  Figure 1 The