If you have seen the flutters of butterflies converging on Brisbane this spring, you will know there can often be too many to count — but that is exactly what locals are being encouraged to do.

Brisbane’s Big Butterfly Count comes amid swarms of migrating caper white butterflies, known scientifically as Belenois java.

“We want to investigate our biodiversity and butterflies are perfect bioindicators,” project coordinator Jutta Godwin told ABC Radio Brisbane.

“They tell us a lot about our environmental health.”

Motorcyclist Greg, from Mount Gravatt, said he turned down a long road to find “flurries” of the white butterflies.

“I slowed right down and slightly changed the direction as I watched these things go past,” he said.

“It was beautiful.”

Yamanto resident Ailsa had a similar experience.

“The whole air was filled with black and white butterflies with black around their wings and little black spots on them,” she said.

Anyone can join in

Ms Godwin said anyone could get involved by tracking species and numbers with their smartphone, or a special paper chart that could be printed off the project’s website.

The count had only just started and would continue until the cooler months.

With the help of a funding grant from the Brisbane City Council, the project — which is being run in conjunction with the city’s catchment groups — will also host webinars and workshops.

Teams will be sent out to catch and identify species in the region.

Very hungry (and picky) caterpillars

While butterfly numbers appeared higher during the migration season, there were things you could do to help ensure populations were maintained.

“Planting native plants is the most important thing,” Ms Godwin said.

“Caterpillars — or the larvae — are very picky eaters.

“Some have barely any plants they like or can digest without dying.”

Ms Godwin said others were able to feed on multiple species.

“It’s really important to have the native larvae host plants in place so that the mums can lay their eggs and the caterpillars can go through their very hungry stage,” she said.

Butterfly and Other Invertebrates Club president Ross Kendall said the most common “host plant” that the species laid its eggs on were Capparis mitchellii, Capparis arborea and the broom bush.

“Each female would lay a group of probably 20 or 30 eggs, they hatch, and caterpillars munch away and strip off all the plants,” he said.

Mr Kendall said when the adults emerged and wanted to breed again, they headed east towards the coast to find somewhere to lay their eggs.

“It’s those hungry caterpillars that are interested in feeding,” he said.

Where have they come from?

Mr Kendall said the caper white was a widespread species and the annual migration could see millions of butterflies move through the city.

He said the species of butterfly usually bred after winter, mostly in the west.

The blue tiger butterfly is also among the species that come out in big numbers over the warmer months.

Thanks to the rain, Mr Kendall said, swarms were being spotted earlier.