Even before they are born, some stick insects can disperse to far-away regions. Scientists find that the eggs of some stick insect species are so hard that even if their mothers are eaten by birds, they can pass through the birds’ guts unaffected and hatch successfully once they come out in their predator’s poop. For an insect that cannot travel very far, this method could serve as an important means of dispersal to new regions.
Like plant stems
Stick insects resemble thin plant stems. But birds can still see through this camouflage and do prey on them. Incidentally, the eggs of many stick insect species resemble seeds in colour, shape, size and texture. This piqued the interest of a team of Japanese scientists: If birds ate stick insect eggs, could they still hatch after they come out in bird poop?
Over 2015 and 2017, the team fed 210 stick insect eggs — of three species found in Japan — along with artificial feed to the brown-eared bulbul, a small bird that feeds on the insects in the wild. When the scientists examined bird poop after the meal, they found that up to 20% of the eggs remained intact. Stick insect eggs take time to hatch, and the team found that two of the intact eggs eaten by the birds in 2017 hatched this February. This provides direct evidence that stick insects can hatch out of eaten eggs and, in turn, could be dispersing to new places that the birds unwittingly take them to.
This is possible not just because stick insects eggs are hard, write the authors in their study published in Ecology. Females of many stick insect species are parthenogenetic: They do not have to mate with a male to fertilise the eggs that they carry in their bodies. So even if they are eaten, their eggs could still hatch once outside their predator's body.
Genetic structure
“Based on this we’d like to investigate whether similar genetic structure of stick insects can be found along birds’ migration flight paths, and whether there are genetic similarities between stick insects and plants that rely on birds for seed distribution,” said lead author Kenji Suetsugu of Japan's Kobe University Graduate School of Science in a press release.
It is indeed possible that stick insect species in India too could show this pattern of dispersal, wrote Suetsugu in an email to The Hindu.
