Psyttalia humilis (Silvestri, 1913)
Fischer (1987) placed humilis in the subgenus Psyttalia within Opius. Psyttalia was subsequently elevated to generic rank by Wharton (1987). The combination Psyttalia humilis (Silvestri, 1913) was first used by Wharton (1989). The species name was misspelled as humilus in Wharton and Gilstrap (1983).
Several attempts were made to redistribute P. humilis from Hawaii to other parts of the world for control of medfly, C. capitata, during the 1920s and 1930s. Shipments made to Israel in 1925/26 and Spain in 1933 either arrived dead or failed to establish in culture (Bodenheimer 1951). Other shipments were apparently equally unsuccessful (Clausen 1978, Wharton 1989).
In addition to the distribution information noted below, Psyttalia humilis has been recorded from Australia (Cameron 1941), Benin (Kimani-Njogu et al. 2001), Bermuda (Thompson 1953, Cameron 1941, Waterson, 1937, Russell 1934, 1935, 1936), Fiji (Lever 1938), Japan (Clausen 1978), and Kenya (Bianchi and Krauss 1936, 1937, Cameron 1941, Le Pelley 1959, Gilstrap and Hart 1987). Verification of these distribution records is complicated by the species identification problems noted below and elsewhere. For example, P. humilis was described from South Africa and P. concolor from North Africa. Since the two are nearly identical, it has been difficult to place material from intermediate areas in Africa (Rugman-Jones et al. 2009). Similarly, P. humilis was shipped from Hawaii to parts of the Mediterranean Region and the Middle East where P. concolor is native. Thus, Psyttalia concolor was initially described from Tunisia and also occurs in Spain, but there are published records of Psyttalia humilis from both localities (Thompson 1953, Cameron 1941).
Kenyan populations were introduced to California in the 2000s and have become established (Yokoyama et al. 2011). Details of establishment and rates of parasitism are provided by Yokoyama et al. (2011).