The paper discusses the Heteroptera fauna in general and the phytophagous species of the family Miridae in particular in their role as pests of alfalfa and clover, especially in seed production. The family Miridae accounts for about 60% of all Heteroptera specimens. The most common species are Goeze. and species of the genus Lygus (syn. Exolygus ). Among the latter, the most common are L. rugulipenis Popp., L. pratensis and L. Gemellatus and H. Sch. They can be found on crops throughout the growing season and are especially abundant in July and August. By sucking out their sap, they damage the youngest of the plant parts, stunting their growth and making them curl and dry up. The affected buds and flowers wilt, turn yellow and fall off and the seeds stay small and shriveled. The resultant seed losses often reach 25-50%, and sometimes there is a complete loss of yield as well. The abundance of Heteroptera can be reduced by providing spatial isolation between new and old seed crops (1.0-1.5 km at the minimum), harrowing the crops in the spring, increasing the frequency of cutting and reducing cutting height down to 4-6 cm, weed removal, and so on. Chemical control is carried out at budding when more than 15 imagoes and larvae are found per meter square or when five imagoes or mature larvae are registered with 10 swings with the insect catcher. The control is performed using chemicals based on malathion, phosalone and endosulfan and most pyrethroids.