In the eight months since the $1.2 million facility opened, more than 135,000 people have seen the butterflies and other crea-tures - almost three times as many as museum staff had predicted.
Just over $797,000 has been taken in admission fees, with the exhibit making a surplus of $86,000 once operational, capital reinvestment and depreciation costs for the period were deducted.
"We are ecstatic it has been so popular, and very happy it has made a surplus in its first financial year. We never expected it to do that," exhibits, development and planning director Clare Wilson said on Thursday.
"It is so nice to have achieved something which has been so universally appealing."
As the word spread about how good the exhibit was, more visitors were coming from outside Otago, Ms Wilson said.
The facility would remain open until at least the end of 2010 and maybe longer if it continued to be popular and financially self-supporting.
The high patronage for the tropical forest would also push the museum's total visitor numbers for the 2007-08 financial year, which ended on June 30, to record levels, Ms Wilson said, although the final tally had not yet been calculated.
Just over 364,000 people visited in the previous financial year.
About 1000 butterflies from 20 different species fly in the forest on any day.
They are imported as pupae from suppliers in the Philippines and Costa Rica.
Ms Wilson and museum director Shimrath Paul and have just returned from signing up a new supplier in Costa Rica and the number of pupae imported weekly will soon rise from 800 to almost 900.
