Aspen Insurance Holdings Ltd yesterday announced a net loss of $151.7 million in a first quarter in which the company shouldered more than a quarter of a billion dollars in catastrophe losses.The Bermuda re/insurer’s after-tax earnings were hit by the earthquakes in Japan and New Zealand, as well as floods and Cyclone Yasi in Australia. These natural disasters resulted in net losses of $255.9 million for Aspen.“The first quarter of 2011 saw an exceptionally high level of natural catastrophes which, combined with historically low investment returns and significant changes implied in new exposure modelling, continue to support a potential improvement in market conditions,” said Chris O’Kane, Aspen’s chief executive officer.“These natural catastrophes had a material impact on our reinsurance segment results, while our insurance segment reported a modest profit in the quarter.“Aspen’s diversified model and solid capital base continue to provide the flexibility to allocate resources to business lines that experience the most pronounced price improvements. Our balance sheet remains strong and we believe that we are well positioned to benefit as the pricing environment improves.”Aspen’s combined ratio, which reflects the percentage of premium dollars spent on claims and expenses, soared to 148.5 percent, or 85.1 percent excluding catastrophe losses, compared with a combined ratio of 110.3 percent, or 86.1 percent excluding catastrophes, for the first quarter of 2010.Gross written premiums were $671.3 million in the first quarter, down 4.5 percent from the prior year, principally in the reinsurance segment.Aspen added that it expects gross written premium for 2011 to be unchanged from its initial guidance at $2.1 billion, plus or minus five percent, with a small increase in premium ceded to be between 10 percent and 14 percent of gross earned premium.It expects combined ratio to be in the range of 105 percent to 110 percent including a catastrophe load of $140 million assuming normal loss experience for the remainder of the year. The anticipated effective tax rate in 2011 remains unchanged in the range of eight percent to 12 percent.Diluted operating loss per share was $2.40 for the quarter, including $3.63 of loss per share from the natural catastrophe events that occurred in the first quarter of 2011, down from diluted operating earnings per share of $0.01 for the first quarter of 2010.Net investment income for the quarter was $55.5 million, compared with $59.4 million in the first quarter of 2010. Net realised and unrealised investment gains included in income for the quarter were $8.4 million compared with $12.3 million in the first quarter of 2010.The company’s balance sheet remained robust with $9.3 billion in total assets, $4.2 billion in gross reserves and $3.1 billion of shareholders’ equity.Aspen entered into an accelerated share repurchase in November 2010 to repurchase $184 million of its ordinary shares. The contract was completed on March 14, 2011 and a total of 6.28 million ordinary shares were cancelled under the programme.