HYM. RES. J. Vol. 19(2), 2010, pp. 244-258 Into the wood and back: morphological adaptations to the wood-boring parasitoid lifestyle in adult aulacid wasps (Hymenoptera: Aulacidae) Giuseppe Fabrizio Turrisi and Lars Vilhelmsen (GFT) University of Catania, CUTGANA, Section of Nature Reserves Management, via Terzora 8, 1-95027, San Gregorio di Catania, Catania, Italy; [email protected] (LV) Zoological Museum, Natural History Museum of Denmark, Universitetsparken 15, DK-2100, Copenhagen, Denmark; [email protected] — Abstract. A substantial sample of the parasitoid wasp family Aulacidae was examined for external morphological characters in the adults that might serve to facilitate ovipositing in and emerging from wood. The character evolution of these traits was evaluated by tracing them on a recently published phylogeny, and their functional anatomy is discussed. Various features might serve as ovipositor guides or to help remove debris during emergence from the wood, and/or to protect vulnerable body parts during emergence. It is possible to infer collaboration between different body parts to achieve the successful completion of these crucial life history stages. Variation among the taxa examined indicates that the contribution ofthe individual body parts to complete these tasks in some instances have changed during the evolution of the Aulacidae. Aulacidae comprises 221 extant species 1995; Jennings and Austin 2004). Hosts are belonging to two genera (Turrisi et al. larval Xiphydriidae (Hymenoptera) and, 2009): Aulacus Jurine, 1807, with 75 species more frequently, Buprestidae and Ceram- and Pristaulacus Kieffer, 1900 (including bycidae (Coleoptera) (Skinner and Thomp- the former Panaulix Benoit, 1984), with 146 son 1960; Barriga 1990; Visitpanich 1994; species. Both genera are represented in all Turrisi 1999, 2007; Smith 2001; Jennings zoogeographic regions, except Antarctica and Austin 2004). (Kieffer 1912; Hedicke 1939; Smith 2001, Parasitizing hosts situated deep within a 2005a, 2005b, 2008; He et al. 2002; Jennings tough, woody substrate requires the adult et al. 2004a, 2004b, 2004c; Turrisi 2004, wasp to overcome certain obstacles. The 2005, 2006, 2007;Jennings and Austin 2006; challenge can be broken down into three Sun and Sheng 2007a, 2007b; Turrisi et al. crucial stages: 1) locating the host inside 2009; Smith and Vilela de Carvalho 2010). the wood; 2) ovipositing through the wood Aulacidae have a fairly good fossil record, on or near the host; 3) emerging from the with 37 described species (Nel et al. 2004; wood after completing the larval develop- Jennings and Krogmann 2009). The oldest ment. Information on the adaptations of record is from the Lower Cretaceous, but Aulacidae are rare (Skinner and Thompson most fossil species are from the Cenozoic, 1960; Quicke and Fitton 1995), often being with taxa recorded from the Upper Eocene part of more comprehensive studies deal- of the Isle of Wight, Baltic, and Paris basin ing with parasitoid Hymenoptera in gen- amber, and the Oligocene of North Amer- eral (Quicke 1997; Vilhelmsen 1997a, ica (Nel et al. 2004). 2003a). Aulacidae are koinobiont endoparasi- The main sources for aulacid biology is toids of wood-boring larvae of Hymenop- Skinner and Thompson (1960), who pro- tera and Coleoptera (Gauld and Hanson vided detailed footage of the behaviour of Volume 19, Number2, 2010 245 Aulacus striatus Jurine, 1807 parasitizing discussing possible function of different Xiphydria camelus (Linnaeus, 1758), and features during oviposition into and emer- Deyrup (1984) in a note on Aulacus burquei gence from the woody substrate. We (Provancher, 1882), a parasitoid of Xiphy- discuss the character evolution of the dria maculata Say, 1836. The female of relevant traits in relation to the recently Aulacus striatus locates the hole bored by published phylogeny of the family by its host, inserts the ovipositor and lays an Turrisi et al. (2009). egg in the egg of the host. When the xiphydriid larva hatches, it contains a MATERIALS AND METHODS small larva of A. striatus. The parasitoid — larva feeds internally, delaying its devel- Taxa examined. We examined a substan- opment until the host larva has fed for tial sample of Aulacidae, containing 54 almost a year and is close to the wood species: 8 Aulacus and 46 Pristaulacus, surface. Before pupating, the host larva representing about one quarter of the tunnels up to the surface but not through described extant species of the family the bark, which is left as a seal. When the (Smith 2001; Turrisi et al. 2009). In addi- hostlarva is abouttopupate, theparasitoid tion, data on the morphology of seven rapidly completes its development, caus- fossil and about 30 more extant species ing the death of the host. The mature were included in the discussion on the parasitoid larva then emerges from the basis of descriptions and/or recent revi- remains of the host and spins a cocoon sions. The depositories of the material outside the host in which it pupates. The examined are listed below, the acronyms aulacid imago emerges about two weeks are according to Evenhuis and Samuelson later, by gnawing a hole through the bark (2004). and the thin cap of debris left by the host (Skinner and Thompson 1960; Deyrup AEIC American Entomological Insti- tute, Gainesville, Florida, 1984). U.S.A. (through the courtesy Concerning host location in Aulacidae, the only behavioural information was of Dr David R. Smith). provided by Visitpanich (1994), who ob- BMNH The Natural History Museum, London, United Kingdom (Dr served a female Pristaulacus sp. antennat- ing wood containing potential host eggs Stuart J. Hine). and probing the eggs with the antennae as BPBM Bernice P. Bishop Museum, Honolulu, Hawaii, U.S.A. well as the ovipositor. There is no anatom- ical information indicating the presence of (through the courtesy of Dr a vibration detecting system similar to the David R. Smith). one employed for host detection by other CAS California Academy of Scienc- wasps parasitizing wood-boring insects, es, San Francisco, California, e.g., Orussidae (Vilhelmsen et al. 2001) U.S.A. (through the courtesy and Stephanidae (Vilhelmsen et al. 2008). of Dr David R. Smith). Since at least some aulacids apparently CNCI Canadian National Collection oviposit through the borehole made by its of Insects and Arachnids, Otta- host (see below), they may rely more on wa, Ontario, Canada (Dr John olfactory clues than on vibration detection Huber). when attempting to locate a host, as DBAC Dipartimento di Biologia Ani- demonstrated for the parasitoid wasp male "Marcello La Greca", family Ibaliidae (Spradbery 1970). Universita di Catania, Museo In this paper we investigate the external Zoologico, 'Turrisi G.F. Collec- morphology of the adults of Aulacidae, tion", Italy. 246 Journalof Hymenoptera Research DEI Deutsches Entomologisches In- MRSN Museo Regionale di Storia Nat- stitut, Miincheberg, Germany urale, Torino, Italy (Guido Pa- (Prof. Joachim Oehlke, Dr An- gliano). dreas Taeger). MZLU Museum of Zoology, Lund HNHM Hungarian Natural History University, Lund, Sweden (Dr Museum, Budapest, Hungary Roy Danielsson). NMW (Dr Sandor Csosz). Naturhistorisches Museum, IBLP Instytut Badawczy Lesnictwa, Wien, Austria (Michael Madl). OLML Warszawa, Poland (Dr Jacek Oberosterreichisches Landes- Hilszczariski). museum, Linz, Austria (Dr ITLJ National Institute for Agro-En- Fritz Gusenleitner). vironmental Sciences, Insect SAMC South African Museum, Cape Systematic Laboratory, Tsu- Town, Republic ofSouth Africa kuba (Ibaraki), Japan (Dr Koji (Ms. Margie A. Cochrane). Yasuda, Dr Kazuiho Konishi). USNM National Museum of Natural LACM Los Angeles County Museum History, Smithsonian Institu- of Natural History, Los An- tion, Washington DC, U.S.A. geles, California, U.S.A. (Dr David R. Smith). ZFMK (through courtesy of Dr David Zoologisches Forschungsinsi- R. Smith). tut und Museum A. Koenig, MCFS Museo Civico di Storia Natur- Bonn, Germany (Dr Dirk Roh- wedder). ale, Ferrara, Italy (Dr Fausto Pesarini). ZIN Zoological Institute of the Rus- MCNC Museo de Ciencias Naturales, sian Academy of Science, St. Canaria Islands: Tenerife, Petersburg, Russia (Dr Sergey Spain (Dr Gloria Ortega). Belokobylskij). MCSN Museo Civico di Storia Narur- ZMHB Museum fur Naturkunde der ale "G. Doria", Genova, Italy Humboldt-Universitat, Berlin, Germany (Dr Frank Koch). (Dr Roberto Poggi). MFNB Museo Friulano di Storia Nat- ZMUC Zoological Museum, Copenha- gen University, Denmark. urale, Udine, Italy (Dr Carlo ZSMC Zoologische Staatssammlung, Morandini). MHNG Museum d'Histoire Naturelle Munich, Germany (Prof. Dr Klaus Schonitzer, Erich Diller, de la Ville de Geneve, Switzer- Dr Stefan Schmidt). land (Dr Bernhard Merz). MNHN Museum National d'Histoire Extant taxa directly examined.—Aulacus Naturelle, Laboratoire d'Ento- bituberculatus Cameron, 1899, A. burquei mologie, Paris, France (Dr (Provancher, 1882); A. digitalis Townes, Claire Villemant). 1950; A. impolitus Smith, 1991; A. pallipes MNMS Museo Nacional de Ciencias Cresson, 1879; A. japonicus Konishi, 1990; Naturales, Madrid, Spain (Dr A. schoenitzeri Turrisi, 2005; A. striatus Carolina Martin). Jurine, 1807; Pristaulacus africanus (Brues, MRAC Musee Royal de l'Afrique Cen- 1924); P. barbeyi (Ferriere, 1933); P. bicornu- trale, Tervueren, Belgium (Dr tus (Schletterer, 1890); P. boninensis Ko- Eliane De Coninck). nishi, 1989; P. capitalis (Schletterer, 1890);P. MSNP Museo Civico di Storia Natur- chlapozvskii Kieffer, 1900; P. compressus ale di Calci, Pisa, Italy (Dr Pier (Spinola, 1808); P. comptipennis Enderlein, Luigi Scaramozzino). 1912; P. editus (Cresson, 1880); P. edoardoi Volume 19, Number2, 2010 247 Turrisi, 2007; P. fasciatus (Say, 1829); P. specimens were fixed with Leit-C-plast on fasciatipennis Cameron, 1906; P. flavicrurus an object table and observed at 1.6 kV (Bradley, 1901); P.foxleei (Townes, 1950); P. using a special low voltage anode (spot galitae (Gribodo, 1879); P. gibbator (Thun- size: 4-5); other specimens were coated berg, 1822); P. gloriator (Fabricius, 1804); P. with a Polaron SEM sputter coater system haemorrhoidalis (Westwood, 1851); P. mst/- prior to observation at 10 kV using a /fln's Konishi, 1990; P. intermedins Uchida, conventionalhighvoltage anode (spotsize: 1932; P. irenae (Madl, 1990; formerly in 3-4). — Panaulix); P iridipennis (Cameron, 1900); P. Morphological terms. Morphological ter- kostylevi (Alekseyev, 1986); P. krombeini minology follows Crosskey (1951), Huber Smith, 1997; P. frufae Turrisi, 2000; P. and Sharkey (1993) and Gauld and Bolton longicornis Kieffer, 1911; P. mmor (Cresson, (1996). Terminology for surface sculpture 1880); P. montanus (Cresson, 1879); P. follows Harris (1979). morawitzi (Semenow, 1892); P. mourguesi RESULTS AND DISCUSSION Maneval, 1935; P. n/ger (Shuckard, 1841);P. occidentalis (Cresson, 1879); P. paglianoi Morphological traits of adult aulacids Turrisi, 2007; P. patrati (Audinet-Serville, directly observed or taken from literature 1833); P. pf/fltoz Turrisi, 2006; P. resufor- are reviewed and briefly described in the ivorus (Westwood, 1851); P. rex (Benoit, following and illustrated prior discussing 1984; formerly in Panaulix); P. rufipilosus their possible functional value in relation Uchida, 1932; P. rufitarsis (Cresson, 1864); to: 1) oviposition and 2) emergence from P. ryukyuensis Konishi, 1990; P. sexdentatus the wood—. Kieffer, 1904; P. signatus (Shuckard, 1841); Head. Frons and vertex: The frons is P. smithi Turrisi, 2006; P. stigmaterus (Cres- smooth or strongly transverse-carinulate in son, 1864) and P. strangaliae Rohwer, 1917, both fossil and extant Aulacus (Fig. 1). A P. thoracicus (Westwood, 1841). — few species of both fossil and extant Fossil taxa evaluated from descriptions. Pristaulacus have the frons weakly trans- Aulacus eocenicus Nel, Waller, Ploeg, 2004 verse-rugulose or striolate-carinulate from the Lower Eocene of the Paris basin (Figs 2-3), while most species of this amber (Nel et al. 2004); Pristaulacus bradleyi genus, including the fossil P. velteni have (Brues, 1910), P. rohweri (Brues, 1910), and the frons smooth, atmost punctate (Fig. 4). P. secundus (Cockerell, 1916) from the In Aulacus bituberculatus and Pristaulacus Oligocene of Florissant (Colorado, U.S.A.) tuberculiceps, the vertex has two prominent (Brues 1910;.Cockerell 1916); P. praevolans posterodorsally directed outgrowths. Sub- (Brues, 1923) and P. mandibularis Brues, antennal grooves: The subantennal 1932 from the Upper Eocene of the Baltic grooves are concavities located below the Amber (Brues 1923, 1932); P. velteni Jen- toruli, accommodatingthe scapeswhen the nings and Krogmann, 2009 from the antennaeareheld inaventralposition,e.g., Eocene of the Baltic Amber (Jennings and duringemergence from the pupa (Vilhelm- Krogmann 2009). sen 1997a). The grooves surround the — Methods of examination. Observation of tentorial pits and extend lateroventrally to external features was carried out on dry the lateral areas of the clypeus. The preserved specimens with stereomicro- configuration of the subantennal grooves scopy and SEM. Digital photographs were is not known for any fossil species. They made using a Nikon Coolpix 4300 4.0 are present but not deep in all examined megapixel digital camera and enhanced species ofAulacus (Fig. 1) and more prom- using Adobe Photoshop CS® software. inentinall examined species ofPristaulacus SEM micrographs were made using a (Fig. 2). Clypeus: All extant species of Philips XL-20. Some pinned and air-dried Aulacidae have a medial process on the 248 Journalof Hymenoptera Research Figs. 1-5. HeadofAulacidae,frontalview: 1,Aulacusstriatus;2,Pristaulacusgibbator;3,Pristaulacusbarbeyi;4- 5, Pristaulacus compressus. Larger triangles indicate the sculpture ofthe frontal area and ofthe vertex, with or without transverse roughness. Smaller triangles indicate the subantennal groove. Arrow inFig. 1 indicates the median tooth-like clypeal process. Arrow inFig. 5 indicates the mandibular groove. Scalebars = 500 urn. anterior margin of clypeus, as does the transverse groove (Fig. 5) on each mandi- extinct species Pristaulacus mandibularis. It ble. Posterior margin of the head and is a forward protruding tooth-like process occipital carina: The posterior margin of in Aulacus and most Pristaulacus (Fig. 1), the head, in dorsal view, is straight or while in P. rex it is a lamelliform process. weakly concave in all fossil and nearly all Themedial process is indistinctin the fossil extant species (Figs 6-8). Fossil and extant Pristaulacus velteni (Jennings and Krog- species ofAulacus usuallyhave no occipital mann 2009). Mandibles: Both fossil and carina, except for a few Australasian extant Aulacidae have robust mandibles, species where a narrow carina is present with a well developed cutting edge. More- (Turrisi et al. 2009). Aulacus spp. may have over, all examined species have a subbasal weakly developed transverse-striolate or Volume 19, Number2, 2010 249 Figs. 6-12. Head and anterior part of mesosoma of Aulacidae: 6, Aulacus striatus (lateroposterior view); 7, Pristaulacus gibbator (dorsal view); 8, Pristaulacus compressus (dorsal view); 9, Pristaulacus comptipennis (dorsal view).Figs 10-12.Positionoftheheadinrelationtothepropleuralengthandtothehindmarginofhead,lateral view;10,UnidentifiedIchneumonidae; 11,Pristaulacuscomptipennis; 12,Pristaulacuscompressus. Arrowsindicate the occipital area, without (Fig. 6) or with (Figs 7-8) occipital carina, or with median groove (9). Triangle in Figs 6, 8, 10-12indicates thepropleura. Scalebars = 500fim (Figs 6-9). 250 Journalof Hymenoptera Research in fossil species. Sculpture ofmesoscutum: The mesoscutum is weakly sculptured (transverse-carinate) in fossil and extant species of Aulacus (Figs 13, 17) and in many fossil species of Pristaulacus. How- ever, other fossil species of Pristaulacus (e.g., P. praevolans and P. secundus) have a moderately transverse-carinate sculpture (Cockerell 1916; Brues 1923). In the extant species of Pristaulacus, the sculpture varies from weakly (in a few species from Fig. 13. Lateral view of mesosoma of Aulacus Nearctic and Palaearctic Regions) to striates. Arrow indicates the anterior margin of strongly (in most species) transverse-cari- mesoscutum. Triangle indicates the lateroventral nate (Figs 15-17). Anterior margin of mmaersgoisncuotfump.roSncoalteumb.arSt=ar50i0nd(iicma.tes the sculpture of mesoscutum: In all known fossil taxa, all extant Aulacus spp., and most extant Pristaulacus spp. the anterior margin of rugulose sculpture (Fig. 6) on the occiput. the mesoscutum is rounded in lateral view Almost all Pristaulacus spp. have an occip- (Figs 6, 11-13, 16). In some extant Pristau- ital carina, but the occiput is smooth lacus spp. it is acute to strongly acute and (Figs 7-9). In fossil Pristaulacus spp. the protruding anteriorly, and in a few species carina is very narrow; in extant species it also dorsally (Figs 14-15). Parascutal cari- varies from very narrow (Fig. 7) to very na: The parascutal carina extends from the wide and lamelliform (Fig. 8), with awidth anterior part of the mesoscutum to the varying from 0.2 to 1.5X the diameter ofan tegula in all Aulacidae examined. In many A ocellus. small clade ofextantPristaulacus fossil and extant taxa the morphology of from the Oriental and Eastern Palaearctic the mesoscutum is not described in detail. regions, comprising P. comptipennis, P. On the basis of a drawing from Cockerell boninensis, P. emarginaticeps, P. excisus and (1916: 103, fig. 9b), the posterior part of the P. insularis, is characterized by a more or parascutal carina is expanded into a para- less wide and deep median groove inter- scutal lobe to cover the tegula in the fossil rupting the occipital carina medially Pristaulacus secundus. In the fossil Pristau- (Hg. 9). — lacus velteni the parascutal carina is ex- Mesosoma. Lateroventral margin of panded, with tooth-like lateral projection pronotum: The lateroventral margin of (Jennings and Krogmann 2009). The lobe is the pronotum is rounded and without a absent in the examined extant species of tooth-like processes in all Aulacus spp., as Aulacus and notooth-likeprocess ispresent well as in all fossil and a few extant above the tegula (Figs 17). In the examined Pristaulacus spp. (Figs 13-14). In the re- extant species of Pristaulacus, the parascu- maining species of Pristaulacus, it is angu- tal lobe is present, and most ofthemhave a lated anteriorly and more or less acute; suprategular tooth-like process (Fig. 18). moreover, in most species, the lateroven- Hind coxae: The configuration of the hind tral margin of the pronotum bears one or coxae is not known in detail in most fossil two anterolateral^ directed tooth-like pro- taxa. In Aulacus eocenicus and a few extant cesses (Figs 15-16). Propleura: The pro- Aulacus spp., no groove is present on the pleura are elongate in all Aulacidae, medial surface of the coxae. In all other forming an extended 'neck' between the extant species of Aulacus a longitudinal head and the rest of the mesosoma (Figs 6, (Fig. 19) or (in a few Neotropical species) a 8-9, 11-12). The propleura are less elongate transverse hind coxal groove is present. Volume 19, Number2, 2010 251 Figs. 14-18. Mesosoma of Aulacidae: 14, Pristaulacus kostylevi (lateral view); 15, Pristaulacus ryukyuensis (laterodorsal view); 16, Pristaulacus compressus (lateral view); 17,Aulacus striatus (dorsal view); 18, Pristaulacus compressus (dorsalview). ArrowsinFigs 14-16indicatethe anteriormarginofmesoscutum. Triangles indicate thelateroventralmarginofpronotum;inFig. 14thereisnotooth-likeprocess;inFig. 16twotooth-likeprocesses arepresent. Arrow in Figs 17-18 indicates the posteriorpartoftheparascutal carina; in Fig. 17itis withouta parascutal lobe and tooth-like suprategular process; in Fig. 18 the parascutal lobe and tooth-like suprategular process (triangle) arepresent. Starindicates the sculpture ofmesoscutum. Te, tegula. Scalebars = 500 urn. When a longitudinal groove is present absent. In the fossil Pristaulacus velteni the (e.g., A. striatus), the hind coxa also has a subapical transverse hind coxal groove is distal lobe (Fig. 19). A transverse hind indistinct (Jennings and Krogmann 2009). coxal groove is present in all extant Tarsal claws: (see Turrisi etal. 2009, fig. 11) Pristaulacus spp. being situated either sub- In all Aulacus spp. the tarsal claws have apically (Fig. 20) or, veryrarely, subbasally only a very small basal tooth-like process; (Turrisi 2006, fig. 15) and the apical lobe is three tooth-like processes arepresentin the 252 Journalof Hymenoptera Research Figs. 19-22. Hind coxae (ventral view), hind coxal ovipositor guide, and orientation of ovipositor during oviposition; Figs 19 and 21, Aulacus sp.; Figs 20 and 22, Pristaulacus sp. White arrow indicates the hind coxal ovipositorguide.Blackarrowindicatestheovipositor.Triangleindicatesthedistalpartofhindcoxae.Scalebars = 500 urn (Fig. 19 fromJennings 2006 in litteris). fossil Pristaulacus praevolans and P. velteni and it is always fused with the second (Jennings and Krogmann 2009); two to six segment of the metasoma, forming a rigid tooth-like processes (mostly four), includ- structure. The petiole is stocky (about as ing the basal one, in the extant species of long as wide) in all fossil and most extant Pristaulacus.— species ofAulacus (Fig. 21), as well as most Metasoma. Petiole: In Aulacidae, the fossil and a few extant species of Pristau- petiole is inserted dorsally on the meso- lacus. In most extant Pristaulacus spp., the soma away from the metacoxal foramina, petiole is elongate and slender, between Volume 19, Number2, 2010 253 two and five times longer than wide reinforce the ovipositor cuticle for drilling. (Fig. 22). Ovipositor: In the fossil Aulacus Instead, the aulacid female employs an eocenicus, the ovipositor is moderately long, ovipositor steering device formed by about 0.9X the fore wing length. In other blocking features at the distal ends of fossil Aulacidae, the ovipositor is not the ovipositor valve interlocking system preserved in its entirety. The length of (Quicke and Fitton 1995). This allows the ovipositor is highly variable within extant aulacid to bend the ovipositor tip laterally, species. InAulacus spp. itvaries from 0.4 to thus facilitating guiding the ovipositor 0.9X ofthe fore wing length. InPristaulacus through the wood. An additional oviposi- spp. itvariesfrom0.6tomorethan2.0X the tor guide in Aulacidae is formed by the fore wing length (usually more than 1.0X). hind coxae (Yasumatsu 1937; Jennings and — Adaptationsfor oviposition in wood. Con- Austin 2004; Turrisi 2004). It is not known cerning oviposition, the main problem for whether the species of Aulacus without a hymenopteran parasitoids of xylophagous coxal groove use the hind coxae to guide larvae is to reach the host concealed inside the ovipositor. In Aulacus spp. with a the wood. The tapering and elongate longitudinal hind coxal groove, the coxae petiole possessed by most extant species when aligned create a longitudinal channel of Pristaulacus (Fig. 22) together with the inwhichthe ovipositoris inserted (Fig. 19), dorsal articulation of the petiole possibly guidingitbackwards and slightlyventrally allows a wider range ofvertical movement (Fig. 21). In all species that have a trans- of the metasoma with respect to the verse hind coxal groove, the coxae mesosoma and may improve the handling (Fig. 20), when aligned form a transverse of the ovipositor. The dorsal insertion of channel guiding the ovipositor anteroven- the metasoma facilitates positioning the trally (Fig. 22) at an angle depending on ovipositor vertically, thus making it possi- the relative positions of the coxae and the ble to employ a long ovipositor (see metasoma. The internal diameter of this Vilhelmsen et al. 2001). It has been sug- channelis alittle widerthanthe ovipositor, gested that the acquisition of the wasp- allowing for small movements of the latter waist in Apocrita, through the modifica- and the opportunity for fine steering. tion ofthe first metasomal segment, served According to Turrisi et al. (2009) the as a key adaptation to parasitism on hosts transverse hind coxal groove was acquired living inside wood (Quicke 1997; Vilhelm- very early in the evolution of Aulacidae, sen 1997b, 2000). Aulacidae and many even ifit is not a ground plan character for other parasitoid wasps with long external the family, and it is retained by most ovipositors have transversely subdivided aulacids. A longitudinal hind coxal groove ovipositor sheaths which might facilitate was acquired twice independently within supporting the ovipositor tip in the early Aulacus in a Holarctic clade and by two stages of drilling (Vilhelmsen 2003a), al- Australasian species (Turrisi et al. 2009). though aulacids hold their ovipositor The shift in orientation of the hind coxal sheaths up, away from the substrate. grooves from transverse to longitudinal The cuticle ofthe ovipositor ofAulacidae implies a change in ovipositor mechanism. is not impregnated with metals, in contrast There seems to be no clear correlation of to some other Hymenoptera that parasitize groove orientation with any of the other xylophagous insect larvae (Quicke et al. features observed (e.g., ovipositor length), 1998). This is probably because aulacids and it is at present unclear to us what oviposit using pre-existing crevices, e.g., advantages this reorientation of the ovi- the borehole made by the host female positor direction may confer. during oviposition (Skinner and Thomp- The two basalmost extant species of son 1960), thus obviating the need to Aulacus (A. wau and Aulacus 'sp. 1') as well