When people think of cockroaches, some may think of the much-smarter-than-a-bug Gregor Samsa, but it takes a special kind of person—a social biologist, really—to think of them as “gregarious.” Yes, these unloved (by humans), trash-eating creatures have social lives too. A recent review in the journal Insectes Sociaux highlights the social behavior of two so-called gregarious cockroach species: Blattella germanica and Periplaneta americana. Although not as sophisticated as eusocial insects like ants or bees, these cockroaches can communicate, recognize kin, and even get “lonely” in isolation. Now we’re getting Kafka-esque.
To talk to and recognize one another, cockroaches use hydrocarbons, molecules that are made of only hydrogen and carbon atoms. These chemical markings help them identify group shelter spots, where they hang out together during the day between nightly foraging runs. (When they are out looking for new shelter or food, they tend to follow the crowd too.) The hydrocarbon signature is unique to each cockroach. Siblings can recognize each other and avoid incest, which is not so great for genetic diversity.
When forced into isolation by lab researchers, these gregarious cockroaches get “isolation syndrome,” taking longer to molt and reach sexual maturity. Isolated cockroaches also have problems courting mates, which hints at the possibility that they learn these sexual behaviors through social contact. That may sound familiar to us humans, but let’s not dive too far into anthropomorphism here. The review’s authors suggest that for cockroaches, social contact is quite literal: in their normal group-living environment, cockroaches crawl all over each other, and it’s this physical contact—much of which can be replaced by a stimulus as simple as poking with a feather—that stimulates their physical development. Group living also keeps them warmer and minimizes water loss.
The social life of the gregarious cockroach is not as sophisticated as a human or even an ant, but it knows better than to go it alone.
*We know, we know: Kafka never actually specifies that Samsa was turned into a cockroach—the original text reads “insect”—but the fact that The Metamorphosis has become connected to cockroaches in the popular imagination says something about the buggers, right? Incidentally, novelist (and noted butterfly expert) Vladimir Nabokov insisted that Samsa was turned into a beetle. He even sketched it out.
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