AN UNUSUAL PREY RECORDFOR TACHYTES CHRYSOPYGA OBSCURUS CRESSON(HYMENOPTERA: SPHECIDAE: LARRINAE)FROM IOWA, U.S.A

Abstract

The genus Tachytes Panzer is a large group of solitary fossorial wasps with over 300 species worldwide and 35 species in America north of Mexico (Bohart 1994). Tachytes has been classified into subgenera (Banks 1942) or into species groups (Bohart and Menke 1976; Kurczewski and Spofford 1986; Bohart 1994). Tachytes are described as hunters of Orthoptera (although two separate workers had noted the aberrant behavior of T. bidens and T. ambidens preying on lepidopterous larvae of the family Geometridae in certain states of the former USSR), and prey specificity is reported to be fairly constant at the family level (Bohart and Menke 1976). Kurczewski and Spofford (1986) delineate the prey of Tachytes by species groups as follows: species in the aurulentus group hunt Tettigoniidae (katydids); the pepticus and distinctus groups hunt Acrididae (true grasshoppers and locusts); the mergus group preys on Tridactylidae (pygmy mole crickets); and in the group exhibiting the most diverse behavior, abdominalis, prey records include Tetrigidae (pygmy grasshoppers), Tridactylidae and Acrididae (for common names of orthopterans, see Capinera, et.al., 2004). Tachytes chrysopyga is a member of the abdominalis group and is reported to store Acrididae (Kurczewski and Spofford 1986). This species ranges from southern Mexico to southern Brazil; however, the subspecies obscurus inhabits the United States and northern Mexico (Bohart and Menke 1976). I had a chance meeting with a female T. chrysopyga obscurus on 26 July 2006 as she was transporting prey to the nest. This incident was my first, and so far only, encounter with this species. At approximately 1415 hrs, the wasp in question flew in and landed at my feet in the lawn of a residential lot in Sioux City, Iowa, very close to the base of a retaining wall constructed of small slabs of broken concrete. She immediately began walking toward an interstice in the wall; but before she could enter, I was able to collect her prey, a snowy tree cricket (Oecanthus fultoni Walker, T.) She ignored my intrusion and walked straightaway into a gap between two concrete slabs. I set a clear plastic jar against the wall; and when the wasp emerged, she was trapped. This T. chrysopyga obscurus was in good condition (only minor fraying on the wings); and, at approximately 13 mm in length, was of a normal size for a female of this species (length range: 13-14 mm; W. J. Pulawski, pers. comm.). Volume 118, Number 3, May and June 2007 321