Since its recent introduction to the United States in 2000, the soybean aphid, Aphis glycines Matsumura, (Hemiptera: Aphididae) has expanded its geographic range throughout most of the soybean growing regions in the United States. In Missouri, the geographic range of the aphid has expanded from 19 counties being infested in 2000 to more than 70 counties in 2004. In its native range of Asia and its latest expansion into North America, soybean aphid is heteroecious and considered to have a narrow host range. Multiple authors (Takahashi et al., 1993; Blackman and Eastop, 2000; Voegtlin et al, 2004) have reported several Rhamnus spp. (Rhamnaceae) as being the primary (overwintering) host(s) of this insect. In North America, it is well documented that the secondary (summer) host is cultivated soybean, Glycine max L. (Fabaceae) (Ragsdale et al., 2004). In addition to soybean, Venette and Ragsdale (2004) state that secondary hosts are restricted to species within Fabaceae as several works (Blackman and Eastop, 2000; Alleman et al., 2002) show that soybean aphid is capable of feeding and reproduction on several fabaceous species albeit with a range of poor to good success. Other works have examined the potential for soybean aphid biology to be supported upon secondary host species in plant families beyond Fabaceae such as the Solanaceae. However, experimental evidence has indicated that species such as tobacco, Nicotiana tabacum L., and potato, Solanum tuberosum L. (Solanaceae), are not likely to support soy bean aphid biology (Fang et al., 1985; Ragsdale and McCornack, 2002; Venette and Ragsdale, 2004). Horsenettle, Solanum carolinense L., is a native perennial solanaceous weed that is commonly found throughout the north-central United States in fields, gardens, and waste areas (Wax et al., 1981). It is considered a noxious weed in many states and key pest for many field cropping systems including soybean and crops commonly rotated with soybean such as corn, Zea mays L. (Poaceae) (Medlin et al., 2001; Wlialey and Vangessel, 2002). WJiile there are several examples of many insect species colonizing horsenettle (Judd et al., 1991; Nichols et al., 1992; Mena-Covarrubias et al., 1996; Nault et al., 1997), the potato aphid, Macrosiphum euphorbiae (Thomas) is the only aphid reported to colonize horsenettle (Leonard, 1963). In this paper, we present our field observations indicating that soybean aphid utilizes and reproduces on horsenettle. This is the first report of soybean aphid utilizing a secondary host species beyond Fabaceae.