Male mating and female postmating performances in cotton mealybug (Hemiptera: Pseudococcidae): effects of female density

Abstract

For insects, female density is closely related to reproductive output. However, little is known about the effects of female density on male mating and female postmating performances. Here, we explored the effects of female density in cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), an invasive, rapidly spreading pest in Asia damaging multiple crops and horticultural plants. Using USB digital microscopes, we investigated the frequency, duration, and intervals of mating for males that were individually supplied with 1, 5, 10, and 15 females. We also evaluated the reproduction of mated females and the sex ratio of their offspring. As the female density increased, males mated with more females while substantially shortening mating intervals. Mating occurred actively at the densities of 10 and 15 females, where males mated four times on average, and some mated 6–9 times. However, mating duration and the observed reproductive parameters of females (preoviposition period, overall period from formation of ovisacs to female death, fecundity, and offspring sex ratio) did not differ significantly with female density. A weak trade-off existed between males’ mating frequency and longevity, but there was no relationship between females’ fecundity and longevity. In conclusion, despite their short lifespan, P. solenopsis males have a high mating capacity, and their mating frequency and intervals can be significantly affected by female density. In contrast, female density has little influence on females’ postmating performance. Our findings indicate the significance of the reproductive biology and life history strategies for rapid establishment and population development of mealybugs in newly invaded regions.

Scientific and technological developments in mating disruption of scale insects

“…This behavioural strategy is particularly beneficial for short-lived insects, such as scale males. A higher number of male copulations and a reduced mating duration and intervals have been observed under laboratory conditions at higher female densities (Silva et al 2013;Tong et al 2019).…”

“…As male scales do not feed and thus are not able to replenish their limited energy budget, the existence of a trade-off between flight activity, mating and longevity is expected, as flight is energy-demanding and thoracic flight muscles expensive to maintain (Denno et al 1989;Legaspi & Legaspi 1998;Mendel et al 2012). For example, a trade-off between the number of copulations and longevity was recently demonstrated in Phenacoccus solenopsis Tinsley (Tong et al 2019). Therefore, it is expected that under MD conditions, when exposed to synthetic conspecific pheromone, males may waste their short window of opportunity for mating, by rapidly spending their energy reserves and strongly reducing their chance of mate location and mating performance.…”

Biology, ecology, and management of cotton mealybug Phenacoccus solenopsisTinsley (Hemiptera: Pseudococcidae)

“…7,18 Male nymphal instars completed their development from 15 °C to 40 °C in India, 7 but died at the 2nd instar stage at 35 °C in China and 40 °C in Pakistan. 9,38 Mating occurs during the day, with a duration ranging from 212 to 290 s. 42 Female adults complete their pre-and oviposition period after mating, and produce eggs at temperatures of 17-32 °C. 9,39 However, they failed to complete oviposition and produce eggs at low (15 °C) and high (35 °C) temperatures in China.…”

“…45 An individual male could mate three to six females in his whole life duration and it mate with one or two females per day 46 (4.5 on average); 47 male mating frequency increases with increasing number of females. 42 Males prefer to mate with 4-day-old virgin female adults, and females play an important role during mating as they attract males 44 by releasing sex pheromones such as 2,2-dimethyl-3-isopropylidenecyclobutyl and methyl 3-methybut-2-enoate (maconelliyl senecioate). 48 Once mating succeeds, a male transfers seminal fluid into the female reproductive tract that alters the ovarian structure.…”

“…46 Mated females have a shorter life span than unmated females: 49 the longevity of an unmated female at 35 °C and 20 °C is approximately one month and 54.8 ± 0.4 days, respectively; by contrast, a mated female lives 20.5 ± 0.8 and 46.0 ± 1.9 days at 35 °C and 20 °C, respectively. 23 Male longevity also is affected by mating activity and frequency: 42 unmated males live 7.0 ± 0.1 days, whereas mated males survive for 1.2 ± 0.2 days at 20 °C. 23…”