PROC. ENTOMOL. SOC. WASH. 109(3), 2007, pp. 689-695 EFFECTS OF TEMPERATURE ON THE DEVELOPMENT AND SURVIVAL OF THE CREEPING WATER BUG ILYOCORIS CIMICOIDES EXCLAMA TIONIS (SCOTT) (HEMIPTERA: NAUCORIDAE) H. Kaneda and Y. Yoshiyasu Laboratory of Applied Entomology, Graduate School of Agriculture, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan (e-mail: great_muta03 1 2@ hotmail.com) Abstract. — The effects of temperature on the development and survival of Ilyocohs cimicoides exclamationis (Scott) were investigated under two photoperiods (15, 18, 20, 22.5, 25, and 28°C under 15L-9D; and 18 and 25°C under 10L-14D). Eggs did not hatch at 15°C and its development was delayed at 28°C. The survival rate of nymphs was significantly lower at 18 and 20°C than those at 22.5, 25, and 28°C. No nymphs reached adults at 18°C under either 15L-9D or 10L-14D. The developmental thresholds for the egg and lst-5th instars were 11.8°C and 13.3°C, respectively. The thermal constants for the egg and lst-5th instars were 270.3 and 626.5 degree-days, respectively. These results suggest that /. c. exclamationis is univoltine and the development of the immature stages is restricted to May to October in Kyoto, Japan. Key Words: aquatic insect, Naucoridae, Ilyocoris cimicoides exclamationis, immature stage, life cycle The family Naucoridae occurs world-wide and contains 413 described species in 39 genera (Sites 2000). Naucorids are oval, flattened aquatic bugs with rapto-rial front legs that are used for predation, and hairy middle and hind legs that are used for swimming (Polhemus 1979, Polhemus and Polhemus 1988). The creeping water bug Ilyocoris cimicoides exclamationis (Scott 1874) is the only naucorid species in Japan. The adult is about 12 mm long and mostly brown, except for a greenish head, pronotum and scutellum; and reddish compound eyes. It occurs in China, Korea and Japan, and lives in submerged vegetation near the banks of fresh-water ponds and lakes (Ichikawa 1996, Haya-shi and Miyamoto 2005). This insect is listed as one of the near-threatened species on the Red List of Japan (Ministry of the Environment 2000) because of recent decreases in local population numbers. Rawat (1939) reported that the nymphal developmental period of the nominotypical subspecies /. c. cimicoides (L., 1758) is about 95 d at an ambient temperatures that varied from 14°C to 23°C. Japanese /. c. exclamationis require about 61 d from egg laying to adult emergence in an aquarium in greenhouse under natural photoperiod conditions during summer (Ichikawa 1996). How-ever, thermal effects on developmental traits of /. cimicoides have not been investigated. We study the effects of temperature and photoperiod on the development and survival of /. c. exclamationis to
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