“…Indeed, it was reported that individuals with no lethal alleles were highly heterozygous for enzymatic loci (PASTEUR, 1974 ;S TEINER , 1979), a quantitative trait (P REVOSTI , 1955) and frequencies of lethal and semi-lethal alleles (M INAMORI & S AITO , 1964;G OLUBOVSKY , 1970 ;O SHIMA et al, 1971). However, other studies failed to show any significant seasonal variation for either allozyme or inversion (LA N GL E Y et al, 1977 ;CA VE N ER & C LEGG , 1981) or deleterious genes (S PERLICH et al, 1963 ;M INAMORI et al, 1973). The (B AND & IVES, 1961, 1968B AND , 1963).…”