Actia. 457 



joint more or less elongated, (in oiir species), in nigrohalterata both 

 first and second joint elongated; arista more or less geniculate. Thorax 

 rectangular or nearly quadratic; three or four postsutural dorso- 

 centrals and two præ- and three postsutural acrostichals; a præsutural 

 intraalar bristle, sometimes weak. Scutellum with three marginal 

 bristle^ on each side, and a pair of small apical hairs, crossing or more 

 or less diverging; generally also a pair of præapical bristles. Three 

 sternopleural bristles. Pteropleura wåth a somewhat small bristle 

 above. Abdomen short ovate, generally somewhat flattened; excava- 

 tion on second segment not reaching hind margin; only marginal 

 bristles and on second segment none, or (subgenus Thryptocera) 

 both discai and marginal, and second segment with a pair of marginal; 

 fifth segment with only marginal or sometimes with more numerous 

 bristles. Genitalia small, more or less hidden. Legs somewhat short 

 and sometimes somewhat robust; middle tibiæ with only one antero- 

 dorsal bristle (Actia) or with rows of long antero- and posterodorsal 

 bristles (Thryptocera); anterodorsal bristles on hind tibiæ unequal; 

 claws and pulvilli small and equal in both sexes. Wings with first 

 posterior cell narrowly open or just closed, ending at apex of wing 

 or very slightly before; discai angle rounded; posterior cross-vein 

 at the middle between medial cross-vein and angle, or nearer to 

 medial cross-vein; anal vein either abbreviated or reaching the 

 margin. Either subcostal, cubital and postical vein with bristles, or 

 only subcostal and cubital vein, or fmally only the latter; the bristles 

 on this stretching at least to medial cross-vein; sometimes bristles 

 also on underside of subcostal vein; a small costal spine. 



The species are parasitic on various Heterocera, but especially 

 on Microlepidoptera. 



The species are rather numerous, about some sixty European 

 species are recorded; 10 have been found in Denmark. 



Table of Species. 



1. Abdomen with discai bristles (Thryptocera (Macq.) 



B. B.) 10. versicolor. 



— Abdomen without discai bristles, at all events on third 

 segment {Actia s. str.) 2. 



2. More than cubital vein with bristles 3. 



— Only cubital vein with bristles 7. 



3. Subcostal, cubital and postical vein with bristles 4. 



— Only subcostal and cubital vein with bristles 5. nigroscutellata. 



4. Antennæ mainly yeliow; subcostal vein with bristles 



only on outer half and the bristles short and dense. . 1. nudibasis. 



