24 Key to Families of North American Insects. 



43. Tarsi four-jointed (five-jointed or heteromerous in the females of one or two 



genera); pubescence of wings not placed in rows or lines; wings not usually 

 broad (PI. -t, fig. 80). (Tetrastichus, Aphelinus, Melittobia, Sympiesis.) 



EULOPHLD^ 



Tarsi three-jointed; wings broad, with the pubescence usually arranged in Itands 



or lines; marginal and stigmal veins united to form a strongly recurved stem. 



(Pentarthron (= Trichogrdmma) TRICHOGRAMMATIDiE 



44. Pronotum extending back to the tegulse, or the latter absent; trochanters some- 



times two-jointed 45 



Pronotum shortened, more or less collar-shaped (PI. 4, fig. 75), not extending 

 back on the sides to the tegulae; trochanters one-jointed 76 



45. Trochanters two-jointed, the second joint sometimes difficult to detect in the 



smaller forms as it is sometimes closely attached to the femur 46 



Trochanters consisting of a single joint 52 



46. Mandibles with four teeth; hind wing with two large closed cells; moderate- 



sized, often brightly colored species. (Lycogaster.) . . . . TRIGONAL 6lD.ffi 



Mandibles with not more than three teeth; hind wing usually without a closed 



cell, rarely with one; small or minute, generally black species 47 



47. Antennse inserted far above the clypeus, near the middle of the face, often on a 



frontal prominence 48 



Antennae inserted low down on the face, close to the upper margin of the 

 clypeus (PI. 5, fig. 86) 50 



48. Winged 49 



Wingless (See couplet 49) A few DIAPRIID-ffi 



49. Marginal vein in fore wings linear, not triangularly thickened; mandibles 



with teeth at tip. Wings with or without a basal cell; radial cell in fore 

 wing sometimes present; antennae usually inserted on a frontal prominence. 

 (Paramesius, Tropidopria, Trichopria, Belyta, Pantoclis) (including BELY- 



TIDM) DIAPRIIDiE 



Marginal vein in fore wings thickened and forming a well developed stigma; 

 mandibles toothed, tip of abdomen simple, fore wings with a closed dis- 

 coidal cell. (Heloras.) HELORIDJE 



50. Abdomen acute or sharply marginal along the sides 51 



Abdomen rounded on the sides; wings, when present, with the radial vein de- 

 veloped, but not complete, leaving the radial cell open; no postmarginal 

 vein. (Ceraphron, Megaspilus) (PI. 5, fig. 85) CER^HRONID.^ 



51. Antennae ten-jointed, rarely with fewer joints, but never more; front wings 



without marginal or stigmal veins and usually without a subcostal vein also. 



(Polygnotus, Isocybus, Platygaster.) PLATYGASTRID^ 



Antennae twelve- or eleven-jointed (if rarely seven- or eight-jointed the club 

 is unjointed, or if ten-jointed the stigmal vein is present) ; marginal and stig- 

 mal vein usually present. (Telenomus, Teleas, Caloteleia, Scelio.) 



SCELIONID^ 



52. First segment of abdomen forming a scale or node (PI. 4, fig. 65 (1); fig. 67 



(1,2)); second segment often also nodiform, the highly mobile pedicel 



