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The mermithid, Hexamermis albicans (SIEBOLD) was recovered from larvae of Lymantria (Porthetria) dispar (L.) collected from various localities in Burgenland, Austria in 1974 and 1975 and from Wfirzburg, Germany, in 1974. It was recovered also from Stilpnotia salicis (L.) in Austria in 1974. The mermithid was recovered from all field collected larval instars. The majority of the nematodes emerged from L. dispar larvae collected as second and third larval instars although some nematodes were recorded from larvae collected as first instar larvae still on the egg mass.Peak emergence occurred in the laboratory during the period June 11-17 of both years, but emergence continued at a much lesser degree through the end of larval development. The nematode was found in both high and low host density populations. In 3 localities studied both years, there was a general increase in the percentage parasitism the second year. However, except for one locality in Austria in 1975 where individual samples produced up to 11 ~o parasitism, the overall parasitism increased from 0.4 ~ in 1974 to only 2.5 ~o in 1975.Because of the continuing spread and costly ravages of the gypsy moth, Lymantria (= Porthetria) dispar (L.), in the United States, numerous methods of controlling this pest are under investigation. One approach, that of classical biological control, is being re-emphasized in an effort to locate new and more effective natural enemies and to re-examine known species of natural enemies for use in new areas of infestation of the moth.As part of this program, personnel from the European Parasite Laboratory maintained a temporary field station at Schutzen-am-Gebirge in Burgenland, Austria, during the spring and summer of 1974 and 1975 to study and collect natural enemies from endemic populations of L. dispar and closely related species of Lepidoptera. Also in the spring and summer of 1974, L. dispar larvae were periodically obtained from an infestation of the moth near Wtirzburg, Germany. METHODS AND MATERIALSIn 1974, larvae of L. dispar were collected weekly at 8 localities in Burgenland ( fig. 1 : sites 3, 5-11) and. every 2 weeks at Wiirzburg. In addition, larvae of the satin moth, Stilpnotia salicis (L.) were collected weekly during the same period from an infestation in Burgenland ( fig. 1 : site 2).

Hyrnenopterous parasites and hyperparasites of Schizaphis grarninum (Rondani) (Horn., Aphididae) on sorghum, in the Drdrne, France For 6 years, the abundance and efficacy of parasites of the greenbug, Schizaphis graminurn (Rond.), were studied in sorghum fields in the Drame Department, south-eastern France. The 10 species of primary parasites recorded included Aphidius erui Hal., A. matricariae Hal., A. picipes Nees, A. rho alosiphi de S. P., A. uzbekistanicus Luzh., Ephedrusplagiator (Nees), Praon allicum Star and P. v o l c r e Hal. (Aphidiidae); Aphelinus asychis Walk. and A. varipes Foerst. (Apielinidae). Tge most common parasites belonged to the genera Pruon and Aphelinus, but they rarely had a determinating impact on the limitation of populations of S. graminurn. Ten s ecies of hyperparasistes in the families Encyrtidae, Charipidae, Megaspilidae and Pteromalidae greatL reduced the efficacy of the primary parasites. Among the 14 different species of primary parasites (over 39 000 mummified cereal aphids) shipped from France to the United States in the frame of a biolo ical control program against S. raminurn, only A. asychis and A. varipes seem to have been establisled. In contrast, two cooperative kological control programs against cereal aphids in Brazil and Chile were successful, owing to a better synchronization in the shipments of exotic parasites by our laboratory and of releases by our collaborators overseas. 1969; INAYATULLAH et al. 1987; PUTERKA et PETERS 1990). La situation est devenue si prkoccupante en quelques anntes, qu'une abondante bibliographie fut publiie par WALKER et al. (1972). I1 devint urgent de contr6ler rapidement les U. S. RQumC Pendant six annies, I'abondance et I'impact des parasites de Schzzaphis gvuminum (Rond.) furent itudits sur cultures de sorgho, dam la Dr6me (Sud-Est de la France). Dix parasites primaires furent rt ertoriis: Aphidius ervi Hal., A. matricariae Hal., A. picipes Nees, A. rhopalosiphi de S. P. A. uzber&istanicus Luzh., Epbedrusplugiutor (Nees), Pruon gallicum Stary et P. volucre (Hal.) [Aphidiidae]; et Aphelinus usycbis Walk. et A. vartper (Foerst.) [Aphelinidae]. Les parasites les plus frtquents aTpaftenaiFnt aux genres Pruon et Aphelinws, mais ils ont rarement eu une action dtterminante dans a limitation des populations du S. gvuminum. Dix espkces d'hyperparasites appartenant aux familles des Charipidae, Encyrtidae, Megaspilidae et Pteromalidae, ont riduit trks fortement l'efficacitt! des parasites primaires. Un total de plus de 39.000 pucerons momifies onr kti envoy& aux $tats-Unis dam le cadre d'un

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