Can you identify this beetle for me?

Hi all,
I began collecting beetles at end of 2011 and happened to come across some beetles which are strange to me. I attached a photo of the biggest of them all and will appreciate if someone can identify it for me. The full body length of this one is 6.3 cm, and it was collected in February 2012, Malaita Province, Solomon Islands.

Thanks much for your help
dainsects.