Yellow butterflies on the wing

Wondering about the presence of large numbers of small yellow butterflies on trees, flowers, roads, and even buildings on Saipan?

It is the season for these yellow butterflies, known by their scientific name as Eurema blanda.

When this type of insect is found in large groups, it is most likely that there are kamachile or acacia trees in that area, according to Dr. Joaquin Tenorio, an entomologist at the Northern Marianas College’s Cooperative Research Extension and Education Service.

In an interview with the Saipan Tribune yesterday, Tenorio said that Eurema blanda butterflies breed on kamachile trees (Pithollecobium dulce).

Tenorio said other host plants for such of insects are Caesalpinia major and Serianthes nelsonii.

He said he is not aware of a Chamorro name for Caesalpinia major plants, but the Serianthes nelsonni, a tree declared as an endangered plant specie, is found on Rota where it is called Tronko guafi.

Plant books listed Hawaii Pearls and Yellow Nicker as common names for Caesalpinia major plants.

“If you go out to an area where you have kamachile trees, they’re (Eurema blanda) breeding in that tree. They’re feeding on the leaves and also sometimes on the flower, but mostly on the leaves. The larvae, the caterpillars, they feed on the leaves,” Tenorio said.

If there’s plenty of them, he said, Eurema blanda could also be spotted flying around other kinds of plants and flowers.

“They fly around buildings, fences and any kinds of structures, especially if there is a large numbers of them. Sometimes you can see them on the road, where there is a puddle of water, drinking,” the entomologist said.

“It is the season for them. During those three times in the year when they come out, they start breeding,” he said.

The females, Tenorio said, would lay eggs in large masses on the kamachile trees and when the caterpillars come out they feed on the leaves.

“It appears to be [the season] right now. They could also appear later on. I’m not sure of the exact month, but that can depend on weather conditions too,” Tenorio pointed out.

He stressed that people have nothing to worry about these butterflies because they don’t pose a danger to health.

Tenorio said the adults are flower feeders, but the caterpillars do the most damage to the host plant, because they feed on a substantial amount of leaves.

It takes 15 to 20 days for the eggs to become adults, said Tenorio, adding that he believes that the adults can only last for several days or weeks.

The adults have two-inch wingspans. Their color is yellow, but the marking on the forewings is dark brown to black.

Tenorio said sometimes, these butterflies lay eggs on flame trees, but the larvae cannot survive on flame trees because these are not their host plant.

Many entomologists believe that Eurema blanda also probably feeds on several other leguminous trees and shrubs. The acacia tree, which is common on the island, belongs to leguminous trees.

The NMC’s CREES has an insect collection at its entomology laboratory where farmers can come and look at the specimens so they could identify what is causing the damage to their plants.