After Heidrick & Struggles posted a large first-quarter loss on Tuesday — and said it would cut more jobs –  the company’s shares plunged $3.94, or 16.9%, to $19.35 at the close of business.

Earlier in the day, the company said the number of executive searches decreased 38.4% compared to the 2008 first quarter, and decreased 6.8% compared to the 2008 fourth quarter.

In addition to an 11% staff reduction back in January,  it now plans to lay off nearly 10% next month. It will also cut discretionary bonuses and reduce base salaries by 5%.

L. Kevin Kelly, the company’s CEO, said the following in a statement:

“The negative impact of the global financial crisis and recession is no longer contained to one or two industries. Each of our practice groups and every region experienced double-digit revenue declines in the first quarter. Search confirmations hit a low in December and showed a modest but steady improvement through March. However, the improvement was not as strong as we had anticipated and operating losses in each region were a result of a cost structure that, despite cost-cutting initiatives, was not supported by first quarter revenue.”

Kelly also said he anticipates an improvement in business in the later half of the year.

“But given today’s environment, nothing is certain,” he added.