Colorful Beetles Have Maternal Instincts: Insects Protect Their Young

Do beetles have maternal instincts? That's a good question. Scientists have discovered that a subfamily of colorful beetles show explicit signs of maternal instincts and care. The findings reveal a little bit more about the earliest stages of social behavior.

Within leaf beetles, only two of the 15 subfamilies display maternal care. More specifically, the broad-shouldered leaf beetles (Chrysomelinae) and the tortoise beetles (Cassidinae) show this type of behavior. Why? Good question. It's possibly because these groups are more vulnerable to predators due to slow-moving and exposed immature stages.

In order to better understand beetle behavior, the researchers examined D. paykulli. This beetle acted aggressively on newly expanded leaves--but the researchers weren't sure why. Once they analyzed video taken of some of the interactions between the beetles and competitors, though, they found out the reason. It turns out that female beetles were in close proximity to eggs attached to the cupped apical leaves.

This wasn't the only species that was seen guarding its eggs, though. Scientists saw other beetles following a tightly arranged group of larvae moving between leaves on their food plant. In fact, mothers sometimes straddled their larvae to prevent their advance down a leaf.

The scientists decided to test the mothers' behavior when it came to guarding their offspring. When they placed a thin stick nearby, the mother reacted aggressively by charging to the edge of the leaf. Charges, stamping and shaking continued for a short period of time after the stick was removed.

The findings reveal a little bit more about how these species protect their young. In addition, it shows a new perspective on selective forces at work during the earliest stages of insect social evolution.

"Large voids remain in our understanding of the natural history of both groups, including the identity and importance of predators and parasitoids and the diverse ways in which mothers may be influencing the survival of offspring," said Windsor, one of the researchers, in a news release. "We urge continued study of these magnificent insects, their enemies and their defenses, both behavioral and chemical, especially in forests along the eastern versant of the Central and South American cordillera."

The findings are published in the journal ZooKeys.