Females of a cricket-like insect found in New Zealand consume male ejaculate after sex to give them enough energy for the following six months of parenting, when they don鈥檛 eat. The size of the secondary genitals they use to collect ejaculate may be related to their success in mating.
Short-tailed ground w膿t膩s (Hemiandrus pallitarsis) are found on the North Island in New Zealand. at the University of Toronto in Canada has spent decades studying the insects after first observing their unique sexual repertoire in a relative鈥檚 garden. 鈥淚 thought, 鈥榃hat the hell is going on?鈥欌�� he says.
An adult male and female of the species first drum their abdomens on leaves to signal their readiness for mating. Things then get weird when they pair off for sex due to the female鈥檚 two sets of genitals. Her primary genitals receive and store the male鈥檚 sperm, while her secondary genitals allow her to receive extra ejaculate in the form of a 鈥渇ood gift鈥�.
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The secondary genitals are shaped like a bent elbow with a forked tip, and the male uses his genitals to grab onto them while he deposits the extra ejaculate on her abdomen.
The extra ejaculate doesn鈥檛 contain any sperm but is full of nutritious proteins. After mating, the female pulls the sticky blob into her mouth and eats it. Gwynne believes the insects do this to sustain themselves for the next six months while they go underground to care for eggs and newly hatched offspring.
鈥淪he doesn鈥檛 eat at all during this time, probably because there鈥檚 no food underground and she can鈥檛 leave her eggs in case a natural enemy comes and does something nasty to them,鈥� he says.
Gwynne and his colleague , also at the University of Toronto, recently discovered that the mating success of female H. pallitarsis depends on the size of their secondary genitals.
They collected 58 females from two sites on the North Island and, by studying the DNA of their stored sperm, found that those with longer secondary genitals had mated with more males.
鈥淢ales may prefer to mate with females that have longer secondary genitals because it signals they鈥檙e of higher quality and able to provide better maternal care, which leads to more offspring,鈥� says Browne.聽鈥淔emales with longer secondary genitals might also be able to secure the male better and prolong the copulation in order to get larger food gifts.鈥�
Unfortunately, females don鈥檛 receive much of a reward for the six months they spend going without food and devoting themselves to caring for their offspring. Once their offspring hatch and go off into the world, females promptly die. 鈥淚t鈥檚 a huge sacrifice for 50 or fewer offspring,鈥� says Browne.
Reference: BioRxiv, DOI:
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