How often are male mosquitoes attracted to humans?

Abstract

Many mosquito species live close to humans where females feed on human blood. While male mosquitoes do not feed on blood, it has long been recognized that males of some species can be attracted to human hosts. To investigate the frequency of male mosquito attraction to humans, we conducted a literature review and human-baited field trials, as well as laboratory experiments involving males and females of three common Aedes species. Our literature review indicated that male attraction to humans is limited to a small number of species, including Ae. aegypti and Ae. albopictus. In our human-baited field collections, only 4 out of 13 species captured included males. In laboratory experiments, we found that male Ae. notoscriptus and Ae. vigilax showed no attraction to humans, while male Ae. aegypti exhibited persistent attraction for up to 30 min. Both male and female Ae. aegypti displayed similar preferences for different human subjects, suggesting that male Ae. aegypti respond to similar cues as females. Additionally, we found that mosquito repellents applied to human skin effectively repelled male mosquitoes. These findings shed light on mosquito behaviour and have implications for mosquito control programmes, particularly those involving the release or monitoring of the male mosquito population.

Keywords: Aedes; disease control; host-seeking behaviour; human-bait collection.

Figure 1.

Proportion of males collected across mosquito species from the literature review of human-baited field collections. Dots show the proportion of males collected out of the total catch, with each dot representing a single study. The red dashed line indicates an equal ratio between male and female catches (0.5 proportion). Data are only presented for species with catches having n > 50 individuals and where males were collected. See electronic supplementary material, table S4 for the complete dataset.

Figure 2.

Comparison of male attraction to humans for three Aedes species in tent trials. The number of male mosquitoes of Aedes aegypti (a), Aedes notoscriptus (b) and Aedes vigilax (c) observed in view of a camera every 20 s. Mosquitoes that were in flight and landed are shown with solid and dashed lines, respectively. Human-baited treatments are indicated in red, with unbaited controls shown in blue. The 95% confidence intervals are shown in grey. Data were averaged across all human subjects, with data for Ae. aegypti males presented separately for each human volunteer in electronic supplementary material, figure S3.

Figure 3.

Relative attraction of female Ae. notoscriptus and male and female Ae. aegypti to different human subjects in pairwise comparisons. The upper row (a–c) shows boxplots of relative attraction between the five human subjects across Ae. aegypti males (a) and females (b) and Ae. notoscriptus males (c). The preference index was calculated by dividing the number of mosquitoes attracted to one human subject over the number of mosquitoes attracted to both subjects. Dots represent the mean attraction of the relevant subject to the other four subjects across eight replicate trials. Comparisons with significant (p < 0.05) pairwise differences are indicated by different letters. The lower row (d–f) presents heat maps displaying the preference index in pairwise comparisons between human subjects. Preference indices are shown on a 0–1 scale, with higher values (red) indicating stronger attraction to subject 1, lower values (blue) indicating stronger attraction to subject 2, and 0.5 (white) indicating no preferential attraction between pairs of human subjects.

Figure 4.

Effect of mosquito repellent applied to exposed skin on swarming and landing by male Ae. aegypti. The number of male Ae. aegypti in view of a camera was recorded every 20 s. Mosquitoes that were in flight and landed are shown with solid and dashed lines, respectively. Repellent-wearing treatments are indicated in red, with non-repellent controls shown in blue. The 95% confidence intervals are shown in grey. Data were pooled across all human subjects.