SOUTH PORTLAND – Credit-card processing company Wright Express Corp, posted lower second-quarter net income and warned that lower fuel costs would weight on its results in the last half of 2012.

Quarterly net income fell to 78 cents a share, or $30.3 million, down from $1.04 a share, or $40.6 million a year ago. Revenues rose to $153.1 million from $141.3 million a year ago.

Adjusted net income, which excludes one-time items, totaled $39.1 million, or $1.00 a share, compared with $35.5 million, or 91 cents a share, a year ago. Wall Street analysts had expected Wright Express to earn 98 cents a share in the second quarter, the company said.

“While we foresee fuel prices becoming a headwind in the second half of the year, we remain confident in our long-term prospects,” said Michael Dubyak, Wright Express’ chairman, president and chief executive. “We plan to continue to invest in our business as fundamentals remain strong and opportunities for growth persist.”

Wright Express, which has about 900 employees, including almost 600 in Maine, in May acquired CorporatePay, a London-based provider of corporate prepaid cards for the travel industry, for about $27.5 million in cash.

That acquisition boosted Wright Express’ presence in the United Kingdom and elsewhere in Europe and expanded its product base to include single-use accounts. The deal was the latest in a series of acquisitions by Wright Express, which acquired Wright Express Australia in 2010 and rapid! PayCard last year.

Wright Express continues to look for potential acquisitions, Dubyak said.

“We are looking. We would like to find some accretive deals, some strategic deals,” said Dubyak. “It’s hard to talk about timing, but we are looking.”

Wright Express recently has signed a contract with with one of Australia’s largest online travel agencies, Dubyak said. Additional details were not immediately available.

For the rest of the year, the company said it expects to see lower fuel prices, costs associated with its recent acquisition of CorporatePay, and adverse effects from foreign currency fluctuations.

“Given the economic environment, we are also anticipating softness in our same store sales to persist,” said Chief Financial Officer Steve Elder.

“The economy is very sluggish. Nobody’s saying we’re going into a recession, but it’s sluggish out there,” Dubyak said. “Sales from existing customers were down 1 percent in Q2. We were hoping to see that be neutral, but that hasn’t happened.”

For the third quarter, Wright Express expects revenues to be in the range of $153 million to $158 million. Adjusted net income will be in the range of $42 million, or $1.08 a share, to $45 million, or $1.15 a share.

For the full-year 2012, the company expects revenues in the range of $591 million to $601 million, and adjusted net income in the range of $156 million, or $4.00 a share, to $162 million, or $4.15 a share.

The company said it based its third-quarter guidance on expectations that U.S. retail fuel prices will be $3.46 a gallon and full-year guidance on the assumption of fuel prices being $3.55 per gallon.

Dubyak said fuel prices are about 35 cents below the company’s initial expectations at the start of the year. Although lower fuel prices are good for consumers, Wright Express makes less money on the fleet or corporate side of its business when fuel prices drop.

Wright Express hedges about 80 percent of its earnings, but 20 percent of its earnings are vulnerable to fluctuations in fuel prices, Dubyak said.