1907.] Wheeler, The Polymorphism of Ants. 5 



viridis Ashm., a Chalcidid fly originally described from specimens collected 

 at large by j\Ir. E. A. Schwarz near San Diego, Texas. 



The genus Orasema, which belongs to the subfamily Eueharinae, was 

 originally established by Cameron on 0. stramineipes from Panama, in the 

 'Biologia Ccntrali-Americana'.^ According to Ashmead,^ this genus is 

 characterized by the possession of 10-jointed antenna? in both sexes, and in 

 having the right mandible two-toothed, the left with a single tooth, and both 

 mandibles acute and falcate at their tips. The genus appears to be largely 

 restricted to tropical and subtropical America but extends somewhat further 

 north in the western than in the eastern portion of the United States. 



The female 0. viridis (PI. I, Fig. 10, and PI. Y, 63 m) measures 2.5-3 

 mm. and is deep metallic green with the clypeus and thoracic dorsum more 

 golden and the gaster blue or violet. The head, thorax and petiole are 

 uniformly and densely punctate, the gaster very smooth and shining. The 

 legs are honey-yellow, excepting the middle portions of the femora, which 

 are metallic green, and the terminal tarsal joints, which are black. The 

 antennae are black, with the basal joints yellow, as are also the mandibles, 

 tongue, and palpi. The wings are very clear and iridescent. The epinotum 

 and scutellum together form a rounded cone through which the thorax 

 reaches a greater vertical diameter than it does elsewhere. The male 

 (PI. I, Fig. 11, and PI. V, Fig. 63 n) is distinctly smaller than the female 

 (2.3-2.5 mm.) and differs in having a much longer petiole, a much shorter 

 and smaller gaster, and longer and thicker antennse, with the basal joints 

 black instead of yellow. 



On opening a large in.s-tabilis nest a dozen or more of these superb insects 

 may be seen lying on their sides or creeping about among the ant-brood 

 (PI. V, Fig. 64). It is also easy to recognize their pupje, white when young 

 or nearly ready to hatch, of a dull blue-green color when mature, scattered 

 among the larvse and pupae of their hosts. Such nests present a splendid 

 appearance, reminding one of a jewel casket in which the sapphires and 

 emeralds are represented by the Orasema, the pearls by the larvte and pupse, 

 the opals by the iridescent wings of the parasites and of the male and female 

 ants> the garnets and bits of jet by the glistening black and red seeds and the 

 red heads and black bodies of the soldiers. 



As soon as the nest is disturbed, the workers seize the Orasemce and thei r 

 pupae and, even at the risk of neglecting their own brood and callows, carry 

 them bodily to a place of safety. In artificial nests this great fondness for 

 the Orasema may be witnessed at one's leisure. The adult parasites are 

 not only carried about and continually licked and fondled, but are also fed 



1 Vol. I. 1883-1900, pp. 104, 105. pi v, fig. 20, pi. vi, fip. 18. 



2 Classification of the Chalcid Flie.s or the .siiperfainily Chalcidoidea. Mem. Carnegie 

 Museum, No. 4, 1904, pp. ix,'.225-5.51, pll. xxxi-xxxix. 



