Taxonomy of the of Pegomya (Diptera: ) developing in the shoots of spurges (Euphorbia spp.) VERNER MICHELSEN

Leafy and cypress spurges are introduced, agressiveweeds that are spreading at an alarming rate in northern North America. In the attempt to find suitable agents for biocontrol of these spurges, the damage potential and host specifityof several of their natural enemies in Europe are being tested. Speciesof anthomyiidsknown to infest shoots of spurges were inves- tigated during 1983-86at the CAB International Institute of BiologicalControl, European Station, Delémont, Switzerland,and prompted the present paper, whichcovers the . What was previouslyrecognized as one variable species, Pegomyaargyrocephala (Meigen), is herein divided into 5 different species: P. argyrocephala(Meigen, 1826);P. curticornis(Stein, 1916); P. euphorbiae (Kieffer, 1909), = transversaloidesSchnabl in Schnabl & Dziedzicki, 1911;P. hybernae sp. n.; and P. lucidae sp. n. Keys and descriptionsto the adults of both sexes are provided, and host plant relations and other biological data are summarized for each species. Field and laboratory observations at Delémont have shown that two species, P. cur- ticornis and P. euphorbiae, are potential control agents of leafy spurge and cypressspurge, re- spectively,and their release in North America recommended. V. Michelsen, Dept.of Entomology, ZoologicalMuseum, Universityof Copenhagen, Univer- sitetsparken 15, DK-2100Copenhagen Ø, Denmark.

Herbaceous perennials of the Euphorbia esula L. shoots of Euphorbia spp. attacked by Pegomya group, the bulk of which are native to central and larvae at various places in central Europe, and I southeastern Europe, include several adventive was provided with samples of reared from this species and hybrids in North America. Some of material for identification. At that time it was as- these, in particular the hydrid leafy spurge (E. x sumed (see Hennig 1973) that a single, rather var- pseudovirgata (Schur) So6) and cypress spurge iable species, P. argyrocephala (Meigen), was the (E. cyparissias L.), are agressive weeds rapidly only anthomyiid borer in the shoots of spurges, spreading in Canada and the American Midwest. but it was realized that 'argyrocephala' might as They preferably invade unmanaged areas and pas- well be an aggregate of sibling species. ture land, where they replace the native flora on The present taxonomic study, based mainly on large areas. Further, these spurges contain a latex material reared by A. Gassmann, eventually which is toxic to many grazing . proved that 5 different species of spurge-boring Several screening programmes on potential Pegomya can be distinguished on purely morpho- agents for biocontrol of the weedy spurges have logical criteria. Independently, the integrity of 3 been carried out. One of these, at the European of these species has been confirmed on other Station, CIBC, Delemont, Switzerland, involved criteria (immature stages, host relations, be- species of gall-forming Pegomya Robineau-Des- haviour, etc.), see Gassmann (1987 and in prep. ). voidy (Anthomyiidae), and was accomplished be- tween 1983 and 1986 Dr D. Schroeder, Mr A. Methods. Descriptive terminology follows McAlpine by for I Gassmann and coworkers. See (1981) except the male terminalia, where use preliminary report gonocoxal lobes (gonopods), gonostyli (parameres), (Gassmann 1987) and Ph.D. thesis (Gassmann in phallus (aedeagus) and parameral proc. [of phallus] prep. ). During 1982-85 A. Gassmann collected (ventrolateral proc.) (McAlpine's terms in paren- 426

tion remained unconfirmed until this subterra- nean gall of cypress spurge eventually was redis- covered in Lothringen (now Lorraine, France) by Kieffer (1893). Similar galls were subsequently found on Euphorbia amygdaloides L. in France (Pierre 1905) and E. lathyris L. in Czechoslovakia (Baudys 1954). It was suggested that these spurge galls were caused by a species of agromyzid or a gall-midge, and it was only in 1964 that Dr H. Buhr succeeded to rear the from galls found on cypress spurge in Thuringia. This proved to be an anthomyiid, which W. Hennig initially identified as Pegomya euphorbiae (Kieffer) (see Hering 1968: 312). In his subsequent Palaearctic mono- graph of the , Hennig (1973) used the senior name P. argyrocephala (Meigen). The 5 species presently recognized in the 'ar- gyrocephala' species group of Pegomya are as fol- lows : 1.argyrocephala (Meigen, 1826)(Anthornyia) sp. rev. 2. curticornis(Stein, 1916)(Chortophila) sp. rev. 3. euphorbiae (Kieffer, 1909)(Agromyza) sp. rev. transversaloides Schnabl in Schnabl & Dziedzicki, 1911(Pegoniyia (Anthomyia» syn. rev. 4. hybernae sp. n. 5. lucidaesp. n.

Description Dark coloured, generally rather short-legged and robust Pegomya of medium size. Wing length 3.5- 6.2 mm. Ground colour of head (incl. antennae and mouthparts), body and legs piceous to black, except anterior parts of head to some extent ful- 1. The and Fig. gall puparium of Pegomya euphorbiae vous in teneral individuals. Head, and as illustrated in Anatomes body legs (Kieffer) by Malphigius 1679, matt bluish- to brownish darker in plantarum, pi. 19 fig. 66. grey pruinose, male than female; also prementum matt by pruinosity but male St V and sclerites of ovipositor black. Five darker theses). Acronyms for specimen depositories are: mainly shining stripes (parame- HNHM-Hungarian Natural History Museum, dian ones narrow) on mesonotum, brown to black- Budapest, Hungary; MNHN-Museum National d'His- ish in colour, often distinct in male but effaced or toire Naturelle, Paris, France; MNHU-Museum fur absent in female. T II-V of male abdomen in Naturkunde der Humboldt-Universit?t, Berlin, GDR; pos- terior view with dark median which fall UMO-University Museum (Hope EntornologicalCol- markings lections), Oxford, UK; ZMUC-Zoological Museum, short of tergal hind margins but often form bands Universityof Copenhagen, Denmark. at fore margins; female abdomen with darker stripe effaced or absent. Wings and calyptrae (ex- cept in tenerals) to dark brown fumose; hal- The Pegomya argyrocephala group light teres pale brownish to blackish. Malpighius (1679: 42, pi. 19 fig. 66), the famous Head large; frontal angle projecting well be- Italian anatomist, described and illustrated a large yond margin of notably short face; genae deep, stem-gall on 'Tithymali ciparissce' (= Euphorbia genals bi- or multiserial. Female frons broad, oc- cyparissias) containing a dipterous puparium, see cupying at least two-fifths of total head width; or- Fig. 1. Curiously, this ancient biological observa- bitals irregular, 3-6 pairs, lower pairs often