OVIPOSITION STRATEGY AND BEHAVIOR OF THE KARNER BLUE BUTTERFLY, LYCAEIDES MELISSA SAMUELIS (LYCAENIDAE)

Lepidoptera are known to oviposit on host-plants singly or gregariously, and each particular strategy is thought to aide in larvae survival. We studied the oviposition strategy of the Karner blue butterfly (Lycaenidae), Lycaeides melissa samuelis Nabokov, which has two distinct broods per year. We found the Karner blue butterfly oviposition strategy differed between the two broods, but fecundity did not differ. The first brood primarily oviposited singly on host-plants (1.06 eggs/location), whereas the second brood oviposited in clumps (2.94 eggs/location). From these data and noted behavior observations, we hypothesize that the change of strategy is due to environmental conditions and the risk associated with larval aggregation. Additional key words: host-plant quality, gregarious, larvae, fecundity, risk The ecology of oviposition behavior in Lepidoptera has been intensively studied from an ecological and evolutionary perspective. Host-plant quality is well known to affect butterfly oviposition preferences and behavior (Grossmueller & Lederhouse 1985; Myers 1985; Singer 2003). Additionally, several studies have focused on the evolutionary causes, benefits, and risks of having gregarious eggs and larvae (Stamp 1980; Courtney 1984; Inouye & Johnson 2005). However, we are not aware of any study which has examined a species that changes oviposition behavior with their particular generation. Data on such behavior changes may provide insights into the trade-offs of ovipositing singly or in larger clumps. Behavior changes may also reveal environmental conditions that correlate with particular oviposition strategies. The federally endangered Karner blue butterfly (Karner blue) (Lycaenidae), Lycaeides melissa samuelis Nabokov, is an inhabitant of oak savanna and pine barrens in the Midwestern and Eastern United States. The Karner blue feeds exclusively on wild blue lupine, Lupinus perennis L. (Fabaceae), always has two broods per year, and has a mean adult lifespan of 3.5 days (Knutson et al. 1999). The life cycle of the Karner blue is described in Figure 1. Throughout the Karner blue range, dry conditions are relatively common during the second brood larval phase, and host-plant senescence at this time decreases leaf nitrogen and water in hostplants (Pickens & Root 2008). The result is likely to be increased second brood larvae mortality and/or poor physical condition of adults. In this study, we report the Karner blue oviposition strategy, oviposition behavior, and estimate the fecundity of females for each of the two broods. MATERIALS AND METHODS Our study took place at four sites in Lucas County, Ohio, USA and the sites were located at The Nature Conservancy's Kitty Todd Preserve (41° 37' N, 083°47' W). The four sites were separated by distances ranging from 75 to 660 meters. The plant community was a black oak/lupine savanna as described by NatureServe (2006). Dominant woody vegetation included Quercus velutina, Quercus ellipsoidalis, and Quercus alba with a tallgrass prairie herbaceous layer. We used modified Pollard-Yates transects (Thomas 1983; Pollard & Yates 1993) to survey Karner blues daily for the first and second brood in 2005. One to three trained observers performed Karner blue surveys throughout all host-plant areas at the four sites. When a female Karner blue was observed, we performed a 15minute behavior observation. During the second brood, 16 of 121 observations were performed for only 10 minutes since a larger population of butterflies was anticipated. If a butterfly was demonstrating obvious oviposition behavior after 15 minutes, we continued the observation for three additional minutes. We recorded oviposition locations, total time of observation, number FIG. 1. Life cycle of the Karner blue butterfly, Lycaeides melissa samuelis. Photograph of adult male by Marcus Ricci. VOLUME 62, NUMBER 3 131 of ovipositions, and substrate of oviposition. Since individual L. perennis are difficult to distinguish in the field (Grigore & Tramer 1996), a single location was recorded if eggs were within the same 1 m2 area. We acknowledge that our definition of clumped differs somewhat from studies where larvae are certain to directly interact with each other. However, plants within 1 m2 experienced similar environmental conditions (e.g. shade, moisture) and might have even been the same individual plant. Two HOBO temperature data loggers (Onset Computer Corporation, Bourne, MA) were placed in an open, sunny area and a well-shaded area at one study site. Temperatures were recorded every 40-minutes and were correlated with survey and oviposition dates and times. SAS 8.01 (SAS Institute 2000) was used for data analysis, and means are reported with ± standard error.