PROC. ENTOMOL. SOC. WASH. 89(2), 1987, pp. 288-295 LIFE HISTORY AND LABORATORY REARING OF PELOCORIS FEMORATUS (UEMIFTERA: NAUCORIDAE), WITH DESCRIPTIONS OF IMMATURE STAGES J. E. McPherson, R. J. Packauskas, and P. P. Korch, III Department of Zoology, Southern Illinois University, Carbondale, Illinois 62901; RJP, present address: Biological Sciences Group, University of Connecticut, Storrs, Connecticut 06268. Abstract. — The life history of Pelocoris femoratus (Palisot de Beauvois) was studied in southern Illinois, and the immature stages were described. The bug was reared from egg to adult in the laboratory. Adults of this univoltine species overwintered in mud and detritus at the bottom of their aquatic habitat and became active in early March. Eggs were found between late April and mid-May and had been glued singly to leaves of Cemtophyllum demersum L. beneath the surface of the water. First instars appeared in mid-May followed by marked overlapping of the subsequent instars. Active adults were last observed in November. This species was reared on Chaoborus americanus (Johannsen) larvae under a 16L:8D photoperiod at 26.7 ± 1.5°C. The incubation period averaged 17.7 days. Durations of the five subsequent stadia averaged 10.5, 9.7, 11.0, 12.6, and 19.5 days, respectively. The naucorid Pelocoris femoratus (Pali-sot de Beauvois) ranges in continental United States from New England south to Florida and west to the Dakotas (Slater and Baranowski, 1978), Kansas, Oklahoma, and Texas (Sanderson, 1982). It occurs through-out Illinois (Lauck, 1959). Scattered notes have been published on this bug's field life history. It is predaceous, feeding on small moUusks, dragonfly naiads, and other aquatic animals (Lauck, 1959; Uhler, 1884). It inhabits various lentic (e.g. lakes, ponds, pools) (Blatchley, 1926; Bobb, 1974; Ellis, 1952; Froeschner, 1962; Gon-soulin, 1973; Hungerford, 1927 [as P. car-olinensis Torre-Bueno; see La Rivers, 1948]; Lauck, 1959; Polhemus, 1979; Slater and Baranowski, 1978; Torre-Bueno, 1923; Wilson, 1958) and the sluggish parts of lotic habitats (Gonsoulin, 1973; Polhemus, 1979) where it is usually well concealed amidst thick growths of aquatic plants (e.g. Alter-nanthera, Cham, Lemna, Mwiophyllum, Nitella) (Bobb, 1974; Ellis, 1952; Gonsou-lin, 1973; Hungerford, 1927; Lauck, 1959; Polhemus, 1979; Slater and Baranowski, 1978; Torre-Bueno, 1903, 1905, 1923; Wil-son, 1958). Adults overwinter at the bottoms of ponds and pools in muck and detritus (Blatchley, 1926; Bobb, 1974; Uhler, 1884) and emerge in spring to feed and reproduce. Oviposition begins in spring (Bobb, 1974; Torre-Bueno, 1 903) and continues at least until the middle of the summer (Torre-Bueno, 1903). Nymphs have been found during the sum-mer (Bobb, 1974; Torre-Bueno, 1903). There appears to be only one generation per year (Sanderson, 1982) although nymphs may be collected in several stages at the same time (Sanderson, 1982; Torre-Bueno, 1903, 1923).