Reproductive Behavior and Development of the Global Insect Pest, Cotton Seed Bug Oxycarenus hyalinipennis

Abstract

Understanding the fundamental life cycle and reproductive behavior of a pest insect is essential for developing efficient control strategies; however, much of this knowledge remains elusive for a multitude of insects, including the cotton seed bug, Oxycarenus hyalinipennis. Here, we report the results of our comprehensive study on the cotton seed bug's life cycle, including mating behavior, adult lifespan, and egg-to-adulthood development. Our findings showed that adult males and females began mating as early as three days after emerging (75%), and the frequency of mating increased to 100% by the fifth day. Mated females commenced oviposition on cotton seeds as early as two days after mating, with a cumulative mean number of 151 fertile eggs oviposited during the first oviposition cycle. Furthermore, around 10% of eggs from both mated and unmated females remained unfertilized. The first instar nymphs began emerging approximately seven days following oviposition. To track their development, we monitored the newly hatched nymphs daily until they reached adulthood. There were five nymphal stages, which cumulatively took roughly 28 to 30 days. Notably, mating positively influenced the survivorship and lifespan of adult O. hyalinipennis. Mated males and females exhibited median lifespans of 28 and 25 days, respectively. In contrast, unmated males and females only lived for a median lifespan of 9.5 days, about one-third that of the mated O. hyalinipennis. Our study provides key insights into the O. hyalinipennis life history for new IPM strategies.

Keywords: Oxycarenus hyalinipennis; egg development; invasive species; longevity of adults; mating behavior; metamorphosis.

Figure 1

Courtship latency, copulation frequency, and copulation duration in Oxycarenus hyalinipennis males and females (n = 20). (a) Three-day-old adults displayed the longest latency to copulate (mean ± SEM: 14.20 ± 2.62), whereas the four- and five-day-old adults exhibited the shortest mean latency (mean ± SEM: 5.263 ± 0.73, and 3.30 ± 0.55, respectively). Copulation latencies are significant at **** p  <  0.0001 and * p  =  0.0262, according to Kruskal–Wallis and Dunn’s post hoc tests. Each dot within the bar indicates a replication. (b) Mating frequencies exhibited a significant surge starting from day 3 after emergence. Both male and female cotton seed bugs below the age of 2 days displayed reproductive inactivity. (c) Adults aged three, four, and five days old showed no effect on copulation duration (mean ± SEM: 98.31 ± 7.09, 126 ± 14.75, and 104.1 ± 8.94, respectively). Each dot within the bar indicates a replication.

Figure 2

The egg-laying patterns of unmated and mated female Oxycarenus hyalinipennis. (a) Newly emerged unmated females were observed daily for egg-laying until it ceased, and the eggs were counted and monitored for development (mean ± SEM: 14.20 ± 2.913, n  =  10). (b,c) A five-day-old unmated male and female were paired for 24 h. Afterward, the male was removed, and the female was left in the container with a cotton seed for oviposition. The eggs were counted and monitored daily to record the number of infertile (b) and fertile (c) eggs. Bars show the mean daily eggs laid per female and the cumulative mean number of eggs oviposited per female (mean ± SEM: 15.54 ± 4.07, 151.8 ± 13.64, respectively; n  =  13).

Figure 3

Developmental times of newly mated female O. hyalinipennis and life stages from egg to adult. Adult females post mating and eggs were monitored daily for the developmental time. (a) Bars show the mean developmental time (days) per female and the cumulative mean developmental time (days) from egg to adult per female (mean ± SEM: 28.96 ± 0.17, n = 50). (b) O. hyalinipennis egg development stages from egg to first instar nymphs. Notably, the eggs undergo color changes, transitioning from white to yellow, and ultimately to orange or pink. (c) O. hyalinipennis developmental stages encompass the progression from egg to adult: mature adults, eggs, five nymphal stages, and a newly emerged adult. Newly emerged adults are pale pink but rapidly turn brown and black.

Figure 4

Effects of mating on the survival of male and female Oxycarenus hyalinipennis: (a) unmated female (red) and mated female (blue); (b) unmated male (green) and mated male (purple). Differences in the survival curves are significant (*** p < 0.0003, ** p < 0.003) according to the Gehan–Breslow–Wilcoxon test.