Acoustic behaviour and flight tone frequency changes in adult Aedes albopictus and Culex quinquefasciatus mosquitoes

Abstract

Species-specific wingbeat frequency of mosquitoes has already been shown to be useful in species identification. However, mosquito identification using their fundamental wingbeat frequency requires proper evaluation along with its morphological and ecological characters. An acoustic study was carried out on four species of laboratory reared mosquitoes Aedes albopictus, Culex quinquefasciatus, Anopheles crawfordi, and Armigeres subalbatus. However, a detailed study on wingbeat frequency and its variation at different points of the adult life stages was conducted for Ae. albopictus and Cx. quinquefasciatus. Recorded wingbeat beat frequency during the different point of adult life stages was analyzed using the Raven Pro 1.6.1 sound analysis software. Result showed that there was a significant difference in the fundamental frequency between four study species (F = 81.62; df = 151; p < 0.001). Wingbeat frequency of Ae. albopictus and Cx. quinquefasciatus observed to be low immediately after emergence from the pupal stage and gradually became peak during the swarming stage which is considered as the species' fundamental frequency. These change in wingbeat frequency during the early adult stages leads to uncertainty in species identification based on the fundamental frequency. Swarming and pairing activities in Cx. quinquefasciatus and Ae. albopictus exclusively depends on the convergence between male first harmonics (M₁) and female second harmonics (F₂) of their fundamental frequency and make combined harmonic frequency at 1400-1500 Hz. Interestingly, this study observed that the frequency of adult male and early stages of female did not converge at the M₁-F₂ harmonics, thereby preventing successful mating. It thus infers that the wingbeat frequency of active male and female have significant role in the selection of potential mates within the species.

Keywords: Acoustic behaviour; Flight tone; Fundamental frequency (FF); Harmonics; Mosquito vectors; Wingbeat frequency.

Fig. 1

Sex wise comparison of wingbeat frequency of Aedes albopictus and Culex quinquefasciatus.

Fig. 2

Wingbeat frequency level of Aedes albopictus at different time points after emergence from pupa. A One hour; B After seven hours; C After 24 h; D After 36 Hours; E During swarming; F Blood fed individuals; G After oviposition.

Fig. 3

Wingbeat frequency level of Culex quinquefasciatus at different time points after emergence from pupa. A One hour; B After seven hours; C After 24 h; D After 36 Hours; E During swarming; F Blood fed individuals; G After oviposition.

Fig. 4

Recorded wingbeat frequency of female Cx. Quinquefasciatus (1) and Ae. Albopictus (2) from the hatching from pupa to adult individual plotted against the Fundamental Frequency (FF) of four female species [An. Crawfordi (3); Ar. Subalbatus (4); Cx. Quinquefasciatus (5); Ae. Albopictus (6)].

Fig. 5

Sound Harmonicof male (Red line) and female (Black lines) wingbeat frequency of Aedes albopictusat different time points after emergence from pupa. Each line represents the harmonics of male (M₁, M₂, M₃) and female (F₁, F₂, F₃) followed by the fundamental frequency (FF). Harmonic convergence (F₂–M₁) was obsrved after 24 h of female with adult male frequency.