Female choosiness and mating opportunities in the blood-sucking bug Rhodnius prolixus

Abstract

We investigated the relationship between female choosiness and mating opportunities in the blood sucking bug Rhodnius prolixus. Rhodnius prolixus females exhibit active discrimination behaviour to male mating attempts which delays or prevents copulation. Female rejection behaviours can be beneficial if mating opportunities are readily available and the pool of males varies in their quality. Thus, the benefits of finding a better quality male may override the cost of rejecting a mating opportunity. Since the availability of mating opportunities is affected by the ratio of sexually active males to females, we randomly assigned focal pairs to arenas with a sex ratio biased toward males, females or without other individuals. More females exhibited rejection behaviour when conspecifics were present, however, no differences were found when the sex ratio was biased toward either males or females. We discuss possible explanations for these results and hypothesize about the adaptive function of female rejection behaviour.

Females of a blood‐sucking bug may adjust their mating decisions according to the risk of ovipositing infertile eggs

“…It supports the hypothesis that female rejection behaviour is flexible and depends on the cost associated with the loss of a mating opportunity (which is less in scenarios with more potentially available males). These results are congruent with previous evidence in R. prolixus , where females significantly increase their rejection behaviour in presence of conspecifics (Pompilio et al, ). Notice however that the total absence of other candidates created artificially in the laboratory, although it represents a cost for the females (and exerts a significant effect), is not considered by them as permanent absence in the future (otherwise, 1° OC females would not have exhibited 45% of rejection behaviour in absence of additional males).…”

“…In fact, the number of eggs (which imply an abdominal distension) could be the cue used by the female to modify their selectivity degree. The positive relation between the weight of females and the number of retained eggs is congruent with this hypothesis since it is possible to predict female rejection or acceptance based on their body weight (Pompilio et al, ). However, even in the case that the egg load can be used as a cue to adjust females' rejection behaviour, it is not probably the reason whereby this behavioural flexibility evolved, since R. prolixus females carrying different number of eggs do not necessary have different reproductive success if they accede to copulate.…”

“…In cases of no copulation, they lasted for 60 min. The insect's behaviour was recorded using a web camera Genius FaceCam 1010 HD (KYE Systems Corp., Taipei, Taiwan) placed 35 cm above the arena and under homogeneous light intensity (15 lux), allowing the experimenter to observe the insects without disturbance (Pompilio et al, ).…”

“…Female rejection behaviour was considered the main dependent variable for two reasons: (i) it was proved to be effective and, thus, imposes a cost for the female who performs it, and (ii) it exclusively reflects the response of the female (since what occurs afterwards, not only depends on the female resistance but also on the male persistence). Female rejection behaviour comprises the following stereotyped behaviours which prevent or delay copula (Pompilio et al, ): (a) abdominal movements: the female shakes her legs and body up and down, impeding the lateral positioning of the male; (b) evasion: the female runs away once the male jump or mount her, avoiding his physical contact; (c) stridulation: once in contact with the male the female rubs the end of her rostrum against the prosternal groove. The stridulatory vibrations migrate from the female to male's body, and then, he stops the copulatory attempt (as already observed in Manrique and Schilman, ); (d) flattening: the female pushes her body against the substrate, impeding the correct positioning of the male's legs; (e) stamping: the female responds to the male mounting by bringing their legs down forcibly on the ground, impeding the male stability; and (f) abdominal raising: once the male mounts the female, she elevates and keeps the abdomen up, avoiding contact of the genitalia.…”

“…During the evaluation phase a female (either 1° OC or 2° OC) was exposed to a focal male and either to the presence or absence of more males (M+ or M−). In this phase, (Pompilio et al, 2016).…”