Faunistic composition and population dynamics of chrysopids were investigated in two old fields in Quebec. Nine species were collected; Chrysopa oculata Say and Chrysopa chi Fitch are dominant and resident. / Parasitism due to Chrysopophthorus americanus Mason has little effect on the reproductive potential of C. oculata and C. chi populations. However, embryonic mortality, resulting from autosomal translocations, is a major mortality factor in both species. Their karyotypes are described and developmental studies conducted on them and Chrysopa lineaticornis Fitch are reported. / Inheritance of wing and cephalic characters was investigated in C. oculata. A population genetics study revealed seasonal selection against the allelic gene B (black gradates) and superior fitness of its recessive counterpart b (green gradates). A meiotic drive mechanism also favors the b allele, and the allele A determining "facial band" expression. / Chrysopa chi exhibits obligatory and facultative prepupal diapause. The field population, however, is primarily univoltine. Voltinism is controlled by two independently segregating autosomal genes; the recessive alleles, in the homozygous state, determine obligatory diapause and, consequently, univoltinism. Diapause termination is reported.

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