Status And Spread Of The Palearctic Lady Beetles Hippodamia Variegata And Propylea Quatuordecimpunctata (Coleoptera: Coccinellidae) In Pennsylvania, 1993-1995

The adventive lady beetles Hippodamia variegata and Propylea quatuordecimpunctata were detected in Pennsylvania in 1992 and 1993, respectively. Surveys of these aphid predators were conducted during 1993-1996 to document their westward dispersion from counties bordering on the Delaware River; their distribution in eastern Pennsylvania is mapped for the first three seasons. Twelve coccinelline Coccinellidae, both indigenous and nonindigenous species, were collected during the first three seasons; the number of sites at which each was found is recorded. Our surveys document explosive colonization of the state by Harmonia axyridis, corroborate evidence of a precipitous decline in numbers of Coccinella novemnotata in much of eastern North America, and support the idea that Hippodamia convergent is no longer a dominant coccinellid in herbaceous habitats in the northeastern states. Classical biological control as an effective strategy of insect suppression began with the use of a coccinellid. In the late 1880s the vedalia, Rodolia cardinalis (Mulsant), was released to suppress populations of the cottony cushion scale, Icerya purchasi Maskell, in California (Essig 1931, DeBach 1964, Hagen and Franz 1973). The project's spectacular results triggered a "ladybird fantasy": a period of inordinate emphasis on exotic coccinellids, characterized by overzealous and generally unsuccessful importation and establishment of additional species (Greathead 1995). Interest in coccinellids for pest suppression eventually gave way to the use of parasitic Hymenoptera and later to synthetic organic insecticides. Ultimately, a more scientific approach to biological control was adopted, the reliance on insecticides lost favor, and interest in coccinellids was revived during the 1960s and 1970s (Gordon 1985, Waage and Greathead 1988, Greathead 1995). The past 25 years have been marked by changes in the coccinellid fauna of the northeastern United States: establishment of nonindigenous species through either intentional releases for biocontrol purposes or unintentional introductions with commerce, coupled with an apparent decline in numbers of certain native species. Studies on adventive lady beetles during this period have included life histories (e.g., Rogers et al 1972, Michels and Bateman 1986); introduction, evaluation, rearing, release, and redistribution (e.g., Shands etal. 1 Received June 14, 1996. Accepted July 31, 1996 2 Bureau of Plant Industry, Pennsylvania Department of Agriculture, Harrisburg, PA 1 7 1 1 0; present address: Department of Entomology, Clemson University, Clemson, SC 29634. 3 Department of Entomology, Clemson University, Clemson, SC 29634. ENT. NEWS107(5) 291-298, November & December. 1996 292 ENTOMOLOGICAL NEWS 1 972, Angalet et al. 1 979); monitoring of establishment and spread (Schaefer et al. 1987, Ellis and Adams 1993, Wheeler 1993, LaMana and Miller 1996, Hoebeke and Wheeler 1996); attempts to determine the origin of North American populations -i.e., deliberate releases or unintentional introductions with commerce (e.g., Schaefer and Dysart 1988, Krafsur etal. 1992, Day etal. 1994); and taxonomic recognition (Gordon and Vandenberg 1991). Attention has also been given to possible adverse effects of Coccinella septempunctata L. and other adventive lady beetles on populations of native coccinellids, and to chang s in structure of native lady beetle communities (Day et al. 1994, Wheeler and Hoebeke 1995, Elliott etal. 1996). Since the late 1970s, four Old World species of the coccinelline tribe Coccinellini have become established in Pennsylvania: C. septempunctata, Harmonia axyridis (Pallas), Hippodamia variegata (Goeze), and Propylea quatuordecimpunctata (L.) (Hoebeke and Wheeler 1980, Ellis and Adams 1993, Wheeler 1993, 1995, unpubl. data). Pennsylvania participated in the 1993 multistate coccinellid project funded by the USDAAnimal and Plant Health Inspection Services' Cooperative Agricultural Pest Survey. The main goal of that project was to determine the distribution of H. variegata (HV) and P. quatuordecimpunctata (PQ) from Maine to Virginia; information derived from surveys in eastern United States was hoped to enhance biological control efforts against the Russian wheat aphid, Diuraphis noxia (Mordvilko), in the western states (Flanders etal., 1993). These two lady beetles recorded from eastern Canada (Gordon and Vandenberg 1991, McNamara 1991), all New England states, NewYork, NewJersey, and Pennsylvania were determined to be extending their range southwesterly (Ellis and Adams 1993). According to Ellis and Adams, future surveys "should continue to delineate the leading edge of HVand PQpopulations. " We, therefore, have continued to monitor the westward spread of these species in eastern Pennsylvania, where populations were restricted initially to counties on or near the Delaware River, and present herein the results of surveys during 1993-1996. Wealso discuss the status of C. septempunctata (C7) and H. axyridis in Pennsylvania, record the native species of Coccinellini collected during surveys for adventive lady beetles, and comment on the possible decline of certain native lady beetles in the state.