Large carpenter bees from various localities in the Kingdom of Thailand were collected, classified and investigated together with those from local collections. A total of 11 species were identified, namely Xylocopa latipes Drury, X. tenuiscapa Westwood, X. nasalis Westwood, X. tranquebarica Fabricius, X. rufescens Smith, X. caerulea Fabricius., X. abbotti Cockerell, X. aestuans Linnaeus, X. verticalis Lepel, X. collalis Lepel and X. basalis Smith. 

The complexity of social life of Xylocopa spp. was found in their lifespan. At the outset they lead a solitary life and then enter into subsocial and quasisocial systems respectively. Twenty of the X. nasalisí buit-in bamboo nests at Kamphaengsaen Campus were investigated. The number of larval and pupal cells were found ranged between 3-15 cells per nest. The intermediate stage which active form may be called "subimmago", was the first time recorded between pupa and adult stage. The sex ratio of male and female per nest was 1:4. The parasitic larvae of Ophelimus sp. (Family Eulophidae) and the predator larvae of Cissites maxillosa (Family Meloidae) were also found in the nest. 

Large carpenter bees spent large amounts of time in the nest guarding against the intrusion of ants Camponotus (Tanaemyrmex) sp. (Family Formicidae). The female carpenter bee would position herself very near the entrance, clinging to the top of the tunnel wall and would block the nest entrance with her abdomen