A note on increasing capture rates of Culex pipiens Linnaeus, 1758 species-group (Diptera: Culicidae) with CDC-CO2 light traps

research, and control of mosquitoes and mosquito-borne diseases. Like many monitoring schemes, effective and efficient protocols are desired (Montgomery et al. 2021), with efficient detection of adult mosquitoes a common first step (Peck et al. 2018). Several types of insect traps and baits have been used to capture mosquitoes, and several studies have directly compared different trapping protocols (e.g. Kline 2006, Silver & Service 2008, Hoel et al. 2009, Dusfour et al. 2010, Roiz et al. 2012, Lühken et al. 2014, Peck et al. 2018, Gorsich et al. 2019, Mwanga et al. 2019, Hou et al. 2021, Jhaiaun et al. 2021, Murindahabi et al. 2022). These previous studies found that trapping effectiveness can vary based on characteristics and or condition of the individual mosquito (species, sex, whether the mosquito had fed or not) and trap (design, location, and attractant). Two common attractants are CO2 and light, both incorporated into the Centers for Disease Control and Prevention (CDC) developed CO2 traps. Because the CDC-CO2 traps are commonly used (Silver & Service 2008, Roiz et al. 2012, Sriwichai et al. 2015), several studies have assessed its effectiveness with different light types and wavelengths. For example, Jhaiaun et al. (2021) found that some species of Anopheles preferred UV LED (377–384 nm) and UV fluorescent (354–468 nm) and some species of Culex preferred UV fluorescent, UV LED, and blue LED (416–428 nm). Some species of Culex (including Culex quinquefasciatus Say, 1823), but not all, are more attracted to UV fluorescent light (354–468 nm) than white fluorescent light (277–400 nm and above 750 nm) (Saeung et al. 2021). Costa-Neta et al. (2017) also found that Anopheles mosquitoes preferred green LED (520 ± 5 nm) compared to blue LED (470 ± 5 nm), both with higher capture rates than the standard white light in a CDC trap. Understanding preferences of target mosquito species can result in increased capture rates. The goal of this study was to compare capture rates of the CDC Miniature Light Trap Model 512 (John W. Hock Company; Gainesville, Florida, U.S.A.) equipped with different lights and wavelengths. Miniature CDC light traps were equipped with the factory installed white incandescent light, or replaced with green incandescent (roughly 520–560 nm, as specifications were not included with the product, CEC Industries Ltd.; Lincolnshire, Illinois, U.S.A.), red LED (620–625 nm, Chanzon Technology Co., Ltd.; Guangdong, China), and UV LED lights (395–400 nm, EDGELEC, Shenzhen Ruidaxin Trading Co., Ltd.; Shenzhen, China). The study site was a fallow agricultural field (38.46° -93.63°) near Calhoun, Missouri, U.S.A., with grasslands and a small pond in the immediate area. Each trap was baited with CO2 by including approximately 0.45 L of dry ice, suspended 1.75 m above the ground, and set out 30 minutes before dusk for a total of three hours during 11 nights from 8–24 August 2021. In each night of sampling, traps were rotated among the four locations in the same field to be able to assess the effect of the specific trapping location on capture rates. Daily capture counts were square root transformed prior to data analysis, with Scientific Note