Nature is weird. A recent discovery by a Japanese scientist has once again demonstrated this. After refuting prior knowledge, Masaru Hojo discovered something that could inspire a horror film script: ants that turn into obedient bodyguards after they receive secret signals from their caterpillar master.
The caterpillars of the Japanese Oakblue butterfly undergo metamorphosis wrapped inside the leaves of oak trees. As immobile and defenseless prey, the caterpillars recruit the help of ants to protect them. When the ants are offered secreted droplets of sugar, scientists have observed them attacking predatory spiders and wasps that come near the caterpillar.
This relationship between the caterpillars and ants was thought to be mutual, with both parties benefiting from the trade of services. However, Hojo started to notice peculiarities in these behaviors: the ants never seemed to return to their nests or hunt for food. In a zombie-esque state, they became fixated on guarding the caterpillar. In a series of lab tests, Hojo discovered that the ants that ate the sugar droplets became aggressive and would not return to their nests, while ants that did not eat the droplets continued to behave normally.
Hojo even witnessed communication between the caterpillar and the servant ants. Whenever the caterpillar turned its tentacles inside out, the ants would start to move around quickly and act more aggressively. This suggested that the caterpillar actually signalled to the ants to attack nearby predators. There are glandular cells near the caterpillar’s tentacles — Hojo believes the caterpillar may secrete chemical signals to stimulate ant aggression. The aggression exhibited by the ants has been linked to the sugary droplets excreted by the caterpillar. Lower levels of dopamine, which controls movement and aggression in insects, was found in ants that had eaten the secretions compared to those that had not. However, the exact chemical compounds in the caterpillar’s magic potion that turn these ants into obedient servants is yet to be discovered.
While mystery surrounds the exact science in this bizarre relationship, it may indicate that the mutual relationships observed in nature may not really be what they appear to be. In this instance, Hojo’s research hints that the relationship may actually be manipulative parasitic behaviour.