Haldeman, S. S. 1844. Descriptions of insects, presumed to be undescribed. Proceedings of the Academy of Natural Sciences of Philadelphia 2:53-55. PDF

Notes: Published between 30 April 1844 and 21 June 1844. See Nolan (1913).

Haldeman, S. S. 1849b. On several new Hymenoptera of the genera Ampulex, Sigalphus, Chelonus and Dorylus. Proceedings of the Academy of Natural Sciences of Philadelphia 4:203-204. PDF
Hale, P.; Lamb, D. (eds.) 1997. Conservation outside nature reserves. Brisbane: Centre for Conservation Biology, University of Queensland, 540 pp.
Hallett, H. M. 1912 ("1911"). A list of Hymenoptera Aculeata recorded for the county of Glamorgan. Transactions of the Cardiff Naturalists' Society 44:92-99.
Hamilton, W. D. 1972. Altruism and related phenomena, mainly in social insects. Annual Review of Ecology and Systematics 3:193-232.