The Lygaeids (seed-bugs) constitute one of the largest families of the order Heteroptera, with more than 4000 known species in the world. Most are phytophagous, with some being either entomophagous or hematophagous. In this study which was carries out during 2000-2001, specimens were collected from fields and gardens in the Karaj area. Identification was carried out using keys based on morphological characters namely shape and venation of membrane, compound eyes and ocelli, spines of legs, color and length of body, and paramere of male genitalia. The identified specimens were confirmed by R. E. Linnavouri (Finland). Among the collected specimens 5 subfamilies, 11 genera and 13 species were identified as followes:
I. Subfamily: Lygaeinae
Lygaeus pandurus (Scop.) 2.Lygaeus equestris (L.)3. Lygaeus saxatilis (Scop.)
II. Subfamily: Orsillinae
4.Nysius cymoides (Spinola) 5.Nysius graminicola (Kolenati)
III. Subfamily: Geocorinae
6.Geocoris megacephalus (Rossi)
IV. Subfamily: Cyminae
*7. Cymus melanocephalus Fb.
V. Subfamily: Rhyparochrominae
8. Beosus quadripunctatus (Muller) 9. Peritrechus gracilicornis Puton
10. Lamprodema maurum (Fabricus) *11. Camptocera glaberrima (Walker)
12. Bleteogonus circumcinctus Rellter 13. Emblethis denticollis Horvath
*14. Eremocoris sp.
Four species marked with astrisks are new for Iran fauna. All species except the first three are new for Karaj. One species namely Eremocoris sp. is new for science, not described here because of being in an unfit state.
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