, MCZ LIBRARY A survey of the Western European Rhipiphoridae including the first record of a Macrosiagon in The Netherlands (Coleoptera) HARVARD UNIVERSITY Wijnand R.B. Heitmans, Theo M.J. Peeters, Jeroen de Rond & Jan Smit

HEITMANS, W.R.B., T.M.J. PEETERS, J. DE ROND & J. SMIT, 1994. A SURVEY OF THE WESTERN EUROPE¬ AN RHIPIPHORIDAE INCLUDING THE FIRST RECORD OF A MACROSIAGON SPECIES IN THE NETHER¬ LANDS (COLEOPTERA). - ENT. BER., AM ST. 54 (11): 201-211.

Abstract: The Palaearctic Rhipiphoridae of Western Europe are listed for The Netherlands and the surrounding countries. Triungulin larvae close to the species of Macrosiagon ferrugineum are reported as new to the Dutch fauna. The phoretic association with Nitela borealis (Sphecidae), angustula and cyanea (Chrysididae) in nature has not been recorded earlier. Westervoort (province of Gelderland) represents the most northern locality in Western Europe of a representative of the genus Macrosiagon, which has a mainly Mediterranean distribution.

W.R.B. Heitmans, Institute of Evolutionary and Ecological Sciences, University of Leiden, P.O. Box 9516, 2300 RA Leiden, The Netherlands. T.M.J. Peeters, National Museum of Natural History, P.O. Box 9517, 2300 RA Leiden, The Netherlands. J. de Rond, Rietmeent 1, 1357 CC Almere Haven, The Netherlands. J. Smit, Plattenbergerweg 7, 6824 ER Arnhem, The Netherlands.

Introduction (National Museum of Natural History Leiden (NNM); Zoological Museum Amsterdam Rhipiphoridae are beetles parasitic on (ZMA)) and the private collections of C.M.J. of diverse orders including beetle larvae Berger (CB), P. Poot (PP) and A.P.J.A. (Cerambycidae and possibly Anobiidae), the Teunissen (AT). Because some Mediterranean larvae of aculeate and nymphal species are known from northerly localities we cockroaches (Clausen, 1940; Selander, 1957). admit the species from southern France to our Some species are highly specialized and attack list. The presence of a Macrosiagon species on just one host species, while others attack hosts previously unknown phoretic associates is es¬ belonging to a number of genera or even fami¬ tablished as new to the Dutch fauna. The ori¬ lies. The Palaeartic species belong to four dif¬ ginal descriptions and the reports on the asso¬ ferent subfamilies: Pelecotominae, Ptilophori- ciations of the beetles and their hosts need to nae, Rhipiphorinae and Rhipidiinae. be consulted to identify the larval stages, since Records of rhipiphorid beetles are scarce neither identification tables nor recently pu¬ and, because of their complex life history, de¬ blished surveys exist. The adult beetles were scriptions of developmental stages are often in¬ identified by the descriptions in literature complete and the life cycle of many of the bet¬ (Gerstaecker, 1855; Chobaut, 1891, 1906a, b; ter studied European and American species is Bétis, 1912; Besuchet, 1956) and via the iden¬ still based on fragmentary results of observa¬ tification table given by Yablokhov-Khnzo- tion and inferences from the habits of the hosts. ryan (1976). The biological nomenclature as In this paper we summarize the general life disposed by Selander (1957) is adopted. We history of the Western European Rhipiphori¬ discuss a number of factors concerning the po¬ dae and list the species and their hosts known tential dispersal capacity of Macrosiagon spe¬ from The Netherlands and the neighbouring cies, such as the climatic condition of the habi¬ countries using records from literature and tat, the vegetation, host finding, the range of from different Dutch museum collections suitable (carrier) hosts and the life cycle. 202 Ent. Ber., Amst. 54 (1994)

Life history (Vespidae) wasps, whereas the Rhipiphorini parasitize solitary (Andrenidae, Anthophori- Female rhipiphorids are short-lived and have a dae, Megachilidae) and subsocial (Halictidae) high fecundity: they may produce several bees. The subfamily is considered as an ad¬ hundreds to thousands of small eggs (0.4-0.5 vanced taxon (Selander, 1957). It is the best mm) either produced separately or in a num¬ studied of the four subfamilies. The triungulin ber of clutches. The number of eggs in the uses a wasp or bee as carrier (phoresy) to get ovaries is determined by the body size of the into a nest where a full-grown larva is at¬ adult beetles, which is, in turn, dependent on tacked. If no carrier is found, or when no suit¬ host size. Hence, body size and fecundity are able host is available in the nest, the triungulin expected to be most variable in the solitary starves. Inside the nest the triungulin larva species that use different host species of diffe¬ first enters its host and feeds on haemolymph, rent size. Large differences in body size of the but later emerges again with the body expand¬ species in the collections indicate that they use ed 6 to 8 times the original length. It then different host species in nature. moults into a grub-like second instar larva that The beetle larvae go through three to four lives as an ectoparasitoid on its still living different developmental stages, all adapted to host, subsequently, followed by the third stage display different biological functions. The larva that consumes the host completely. The number of moults and the characteristic forms third and presumably last stage larva is elon¬ of the larvae may differ in the distinguished gate en greatly curved, with large fleshy pro¬ subfamilies. The first stage larva is of a cam- cesses on all segments, and the legs short, podeid or triungulin (= three claw) form. fleshy, and non-functional. The mature beetle Triungulins possess a prognathous head with larva first seals the cell of its former host and strong mandibles, antennae, eyes (or ocelli) spins a cocoon before pupation. (Chapman, and a body with well-developed legs often 1870; Grandi, 1936; Clausen, 1940). The adult with the tarsi terminated in transparent leaf¬ beetles leave the host’s nest and mate outside. like pulvillae. The mandibles and legs are Rhipidiinae are highly specialized and adapted to cling to an that happens to known as koinobiont endoparasitoids of cock¬ pass near the triungulin or is actively hunted. roaches. That they also use caterpillars as Triungulins may show fast movements to hosts (De Peyerimhoff, 1942) is unlikely, cling to a host. The larva of Rhipiphorus spe¬ since Barbier (1947), Riek (1955) and cies also have a terminal abdominal segment Besuchet (1956) showed that cockroaches are adapted as a sucker to attach to a wing of a car¬ the exclusive hosts for quite a large number of rier host (Chobaut, 1906a, Tomlin & Miller, species. All Rhipidiinae are probabaly highly 1989). The second stage larva is grub-like, host specific parasitoids. The female beetles legless and eyeless and lives in or attached to are larviform with small eyes, atrophied its host. In the species of the temperate clima¬ mouth particles and no traces of wings. The tic zone this stage may go into diapause. In the elytra of the males are also strongly reduced, Rhipidiinae the diapausing form is followed but they can fly with the hind wings. The tri¬ by a third instar larva, but in the Rhipiphorinae ungulins do not use a phoretic carrier, but ac¬ no such diapausing larva seems to exist. The tively hunt for a young cockroach nymph. The second instar probably develops directly in the pulvillae of the tarsi are absent. The triungulin third and final stage that consumes the host will partly enter the body of the captured host. (see below). The mature instar larva spins a Then it moults by leaving the triungulin exuvi- cocoon before pupation. um outside and develops into a legless endo- Rhipiphorinae are idiobiont parasitoids of parasitic second instar larva. In Rhipidius spe¬ the mature larvae of aculeate Hymenoptera. cies from the temperate climate the second The Macrosiagonini use solitary (Tiphiidae, instar larva may go into diapause and hiber¬ Scoliidae, Eumenidae, Sphecidae) and social nate in the living cockroach. Next year the Ent. Ber., Amst. 54 (1994) 203 third instar then slowly grows in its growing rarely found in woodlands in Germany, Po¬ host and finally kills it by consuming the inter¬ land, Austria and further into northeastern nal parts of the by then mature nymph or adult Europe (Horion, 1956; Lucht, 1987). The spe¬ cockroach. The mature, fourth stage larva has cies has never been collected in The Nether¬ six small, but functional legs. It leaves the lands and Belgium. body of the dead cockroach. Subsequently, it searches a place to spin a cocoon to pupate Ptilophorinae (Sundevall, 1831; Stamm, 1936; Barbier, 1947; Riek, 1955; Besuchet, 1956). The Pelecotominae and Ptilophorinae con¬ Evaniocera dufouri (Latreille) tain the least specialized members of the group. Their systematic position is very differ¬ Immature stages and the host(s) of this species ent from both the Rhipiphorinae and Rhipidii- are unknown. The adult beetles remarkably nae (Selander, 1957). For example, the elytra vary in body length from 3.8 to 11.2 mm and hind wings of the adult beetles are not re¬ (n=46) in both the males and females (NNM, duced and the mouth particles are less atro¬ ZMA, AT, CB). phied. Their life history is obscure; immature Evaniocera dufouri is known from south¬ stages are unknown. The hosts are virtually ern France and is widely distributed in unknown, although the larvae of Rhipistena Mediterranean countries up to the Caucasus cryptartha Broun likely feed on larval Ceram- (Csiki, 1913). It also occurs in Algeria and bycidae of the genus Prionoplus Westwood in Morocco. The most northerly locality in New Zealand, whereas the adult beetles of the Europe is Hungary (NNM). European Pelecotoma fennica (Paykull) have been associated with wood burrows of Ptilinus Rhipiphorinae beetles (Anobiidae) in old willows {Salix spp.) near rivers in June and July (C. Besuchet, per¬ (Macrosiagonini) sonal communication). It has been suggested that the triungulins might be active hunters like the Rhipidiinae preying upon the larvae of Metoecus paradoxus (Linnaeus) different species of wood boring beetles. Schumann (1899) suggests that P. fennica Metoecus paradoxus is chiefly a parasitoid of might also parasitize larvae of the sphecid the larvae of the common yellow jacket wasp Trypoxylon clavicerum (Lepeletier & Serville) Vespula vulgaris (Linnaeus), but it may occa¬ nesting in the abandoned burrows of Ano¬ sionally occur in the nests of V. germanica biidae, but substantive evidence is lacking. (Fabricius) and V. rufa (Linnaeus). Body length varies from 7.8 to 13.3 mm (n=73). The species is commonly found in almost Survey of rhipiphorid species of The all European countries and further into eastern Netherlands and neighbouring countries Europe and Russia (Chapman, 1870, 1891; Hoffer, 1883; Horion, 1956; Yablokhov-Khnzo- Pelecotominae ryan, 1976; Lucht, 1987; Drees, 1994). It was previously the only autochthonous rhipiphorid Pelecotoma fennica (Paykull) known from The Netherlands. Brakman (1966) still refers to the localities Soest (cen¬ The beetle is probably a parasitoid of wood tral part of The Netherlands) and Roermond boring Anobiidae in decaying wood (see (southern part) as given by Everts (1903) above). It is a small and slender species (3.8- (NNM, ZMA). More recent records show that 5.0 mm, n=12, NNM, ZMA). M. paradoxus occurs in almost all Dutch pro¬ Pelecotoma fennica is a northern species. vinces (Peeters & Heitmans, unpublished). 204 Ent. Ber., Amst. 54 (1994)

Macrosiagon ferrugineum (Fabricius) Macrosiagon praeustum (Gebier)

Macrosiagon ferrugineum is a parasitoid of a Immature stages of this species and host(s) are number of different hollow stem and twig unknown. Female body length: 3.3-7.1 mm nesting eumenid wasp species including Euo- (n=7) (NNM, ZMA), males are not present in dynerus variegatus (Fabricius) (syn. Odynerus the collections examined. crenatus (Lepeletier)), E. disconotatus (Lich¬ Distribution: southern France and almost tenstein) (syn. O. crenatus sensu Bliitgen), all other Mediterranean countries, also known Symmorphus murarius (Linnaeus) (syn. O. from Algeria, Russia and Siberia (Csiki, 1913; nidulator Saussure) and Rhynchium oculatum Yablokhov-Khnzoryan, 1976). (Fabricius), but it is also reared from a nest of a Eumenes species (Chobaut, 1891; Bétis, 1912; (Rhipiphorini) Grandi, 1936; Flubenthal, 1929; Van der Vecht & Fischer, 1972). Body length varies in fe¬ males; 4.9-8.1 mm (n= 14) (NNM, ZMA, CB), Rhipiphorus subdipterus Bose the only male present: 7.1 mm (ZMA). Distribution: southern France and almost all This species is a parasitoid of solitary and sub¬ other Mediterranean countries; the species is also social bees, e.g. Elalictus sexcinctus (Fabri¬ known from (sub)tropical countries in Asia cius) (Chobaut, 1906a; Bétis, 1912). Most (India), North Africa (Egypt) and even West specimens in the collections are females Africa (Senegal) (Gerstaeker, 1855; Csiki, 1913). (NNM, ITZ, AT). Female body length: 4.5-9.2 mm (n=29), males: 6.5-8.4 mm (n=4). Distribution: southern France and almost Macrosiagon tricuspidatum Lepechin all other Mediterranean countries. Macrosiagon tricuspidatum uses a number of different eumenid wasp species and perhaps Rhipidiinae Megachile bees as hosts (Chobaut, 1906b; Bétis, 1912). Euodynerus species may have their nest in abandoned nests of other acule- Rhipidius pectinicornis Thunberg ates. Therefore, the record of Megachile as host may be incorrect. Rhipidius pectinicornis is a parasitoid of the The beetles vary greatly in body size. Most German cockroach (Blattelia germanica specimens are females. Female body length: (Linnaeus)), a household pest of tropical ori¬ 4.0-12.8 mm (n=80), male: 6.0-8.0 mm (n=2) gin. At the beginning of this century De (NNM, ZMA, CB, PP, AT). Meijere reared two larviform females of this Distribution: southern France and almost species emerged from cockroaches from all other Mediterranean countries; also known Amsterdam. It is unknown whether these spe¬ from Russia and Egypt. The records of M. tri¬ cimens emerged from one single host or from cuspidatum in southwestern Germany includ¬ two hosts. The specimens are of equal body ing Hessen, Nordbaden (Mannheim) and the length: 5.0 mm (NNM). Rhipidius pectinicor¬ Alsace (France) are all from the nineteenth nis was listed as part of the Dutch fauna by century. Horion (1956) and Lucht (1987) do Everts (1922). The beetle is known particular¬ not confirm the presence of any Macrosiagon ly from ships infested with German cock¬ species in Germany and doubt whether M. tri¬ roaches in Calcutta (Sundevall, 1831), in cuspidatum really occurs in Kärnten and Denmark (Stamm, 1936) and in Egypt Steiermark (southern Austria). However, 13 (Barbier, 1947). In cooler areas R. pectinicor¬ specimens of M. tricuspidatum from neigh¬ nis can possibly maintain itself in heated buil¬ bouring Hungary and one from Bulgaria are dings with its host, but no new records were present in the collections of NNM and ZMA. reported in the world since 1947. The origin Ent. Ber., Amst. 54 (1994) 205

Fig. 1. Ventral view of triun- gulin larva of Macrosiagon sp. on Nitela borealis from Westervoort, attached to the arolium between claws of left hind tarsus.

and natural habitat of R. pectinicornis are un¬ ryan, 1976; Lucht, 1987). The species is known. present in the collection of AT from Switzer¬ land, but we do not know any record from The Netherlands and Belgium. Rhipidius quadriceps Abeille de Perrin

This species is parasitic on Ectobius cock¬ Rhipidius abeillei Chobaut roaches, particularly E. sylvestris (Poda). Rhipidius quadriceps is known from Ger¬ Rhipidius abeillei is closely related to R. qua¬ many, Austria, Switzerland, France, Italy, driceps. It is likely to be a parasitoid of Spain, Russia, .Finland and North Africa ectobiid cockroaches. Body length of males (Kraatz, 1891; Chobaut, 1919a, b, 1922; Es- from France: 5.0-6.5 mm (n= 21) (AT, ZMA). panol Coll, 1942; Lindberg, 1955; Horion, The female and immature stages are unknown. 1956; Besuchet, 1956; Yablokhov-Khnzo- Rhipidius abeillei has a more southern distri-

Fig. 2. Dorsal view of triun- gulin larva of Macrosiagon sp. on Nitela borealis from Westervoort, anchored to metatarsus under the apical spores. 206 Ent. Ber., Amst. 54 (1994)

Fig. 3. Lateral view of triun- gulin of Macrosiagon sp. on Chrysis angustula from Wes- tervoort, attached to seta of right mid tibia.

bution than R. quadriceps; France, Spain, Alge¬ New Dutch records ria (Espanol Coll, 1942; Besuchet, 1956). In 1990 and 1991 five identical triungulin lar¬ vae attached to three different species of acu¬ Rhizostylops inquirendus Silvestri leate wasps were collected at a railway siding on a sandy embankment in Westervoort near This species is only known from one single, the city of Arnhem. The collecting site faces larviform female, her eggs and the emerged south and rises ± 5m above the surroundings triungulin larvae from Italy once taken from a that consist of a clay soil deposited by the soil sample (not seen) (Silvestri, 1905). The IJssel river. Oak and elm trees surround the male and other immature stages as well as the territory; shrubs such as Symphoricavpos ri- host(s) are unknown. vularis Suksd., Syringa vulgaris L., Crataegus

Fig. 4. Close-up of head with mandibles, maxillary palps, antennae and the light sensi¬ tive organs (ocelli) of triun¬ gulin of Macrosiagon sp. Ent. Ber., Amst. 54 (1994) 207

Table 1. Carrier host species and family, sex of the carrier, collecting date, number and position of the triungulins. carrier host host family sex of coll, date no. of position of carrier triungulins triungulins

Chrysis angustula Chrysididae 9 June 1, 1990 2 one on left Schenck () and one on right mid tibia

Trichrysis cyanea Chrysididae S July 2, 1991 1 right hind (Linnaeus) (Chrysidinae) tibia

Nitela borealis Sphecidae S July 2, 1991 2 both on left Valkeila (Larrinae) hind tarsus monogyna Jacq., Rubus saxatilis L. and R. plantation of the antenna, one below of it (fig. 4). idaeus L. are present in abundance. The insect Antennae implanted in the margin of the head, and plant species at the site were listed in a length 0.096 mm. They consist of 3 segments: I, KNNV-report (Smit, 1991). the shortest and widest segment in the form of The wasps with triungulins were part of a ring, II, the longest segment, flattened, III, of a sample of insects collected by hand near and thin pin-like structure. Rattened sensory appen¬ on a dead oak tree (table 1). The triungulins dix on antennal joint II forming a fork-like struc¬ did not release their grip during preservation ture with the apical part of the joint (figs 3 and 4). of the wasps. The triungulins attached to the Labrum very prognathous, distinct, split into two tibia of Chrysis angustula Schenck and halves ending in a dorsal furrow, that extends Trichrysis cyanea (Linnaeus) all firmly held a further backwards and has half the length of the seta in the mandibles (fig. 3). One triungulin head (not visible in figs 1-4). Mandibles strong, on Nitela borealis Valkeila clung to the aroli- curved to hold a structure in a firm grip. um between the claws of the tarsus (fig. 1) and Maxillary palps consist of 3 cylindrical seg¬ another specimen was found under the spores ments, I and II short and about equal in length, III of the tibia on the tarsal base holding a piece about 2 times as long as II; labial palps rudimen¬ of soft cuticula of the articulation (fig. 2). Fig. tary or absent (fig. 4). Two small pairs of dorsal 4 shows the head of a released triungulin. setae in front of the head, a single pair of small setae on the margin of the head and another sin¬ gle pair of posterior setae implanted just above Description the eyes (figs 2 and 4). Hexapod larva. Average length of the body of One single pair of setae on each of the tho¬ dried triungulins (without the caudal setae): racic tergites and stemites. Trochanters with a 0.33 ± 0.06 mm (n=4), strongly dorso-ventral- single seta as long as the coxa (fig. 1). ly flattened. Three pairs of setae on the abdominal ter¬ Body colour: overall dark brown; head, ter- gites: one dorsal pair, one pair on the marginal gites, stemites and legs strongly sclerotised, edges and another single pair on the lateral ter¬ only the tarsal pulvillae and a similar structure gites. The eighth and ninth segment have only posterior of the abdomen are transparent. 2 pairs of setae of which the outer pair on the Head large, 0.12 ± 0.03 mm, somewhat trian¬ ninth is extremely long, 0.10 mm. Also, 3 gular of shape, tapering off in front, considerably pairs of setae on the abdominal stemites, except longer than the combined lengths of the first and for the eighth segment with 2 pairs of which the second thoracic tergites. Frons indistinctly fused outer pair is longer and both the ninth and tenth with the clypeus. Simple eyes placed laterally on segment with only a single pair (figs 1 and 2). the back of the head behind the antennae. Eyes (Grandi (1936) illustrated a fourth outer pair of consist of four light sensitive structures (Grandi very small setae on the second and third ab¬ (1936) calls them ocelli): three above the im¬ dominal stemite, but that could not be observed 208 Ent. Ber., Amst. 54 (1994) in our dry material). Terminal abdominal seg¬ details to those illustrated and described by ment with a small pulvillus-like structure (fig. Grandi (1936), yet we can only conclude that 3), unlike the sucker of Rhipiphorus species the triungulins from Westervoort are closer to (Tomlin & Miller, 1989). M. ferrugineum than to M. tricuspidatum. Without knowing the adult beetle it is not pos¬ sible to identify a Macrosiagon triungulin cor¬ Identification rectly to species level. Unfortunately, the adult The identification of triungulin larvae to the beetle has not been captured. subfamily level offers no particular problems, although the information is far from complete. Discussion Differences are sufficiently described and illu¬ strated for the Rhipiphorinae and Rhipidiinae The finding of Macrosiagon triungulin larvae (Sundevall, 1831; Chapman, 1870; Chobaut, in two successive years on the same spot sug¬ 1891, 1906a, b, 1919; Silvestri, 1905; Grandi, gests that a population has become established 1936; Barbier, 1947; Besuchet, 1956; Tomlin in the most northerly locality of Western Euro¬ & Miller, 1989). Species are best recognized pe known for this genus. All European Macro¬ by the chaetotaxy and the presence of tarsal siagon species are generally considered to be pulvillae. In combination with the type of car¬ faunistic elements of the Mediterranean region rier host it was easily to identify the species as (Schilder, 1926). It is most likely that one of the Macrosiagonini, Rhipiphorinae. Primary lar¬ three species mentioned in this paper from sout¬ vae of Macrosiagonini have a dorsal furrow hern France up to the Haute Loire is the best from the front to the middle of the head. candidate to migrate to the cooler northwestern Triungulins of the genus Macrosiagon are part of Europe. In Eastern Europe all three characterized by one dorsal pair of remarkably Macrosiagon species seem to be distributed as long setae on the ninth abdominal segment as far as the Caucasus, whereas early records of described above. Another pair of ventral setae M. praeustum are even reported from Siberia on the eighth abdominal segment is about 1/3 (Csiki, 1913; Yablokhov-Khnzoryan, 1976). of this length (fig. 1). Both these abdominal European Macrosiagon species are known setae are much smaller in Metoecus and are from arid zones, such as sand dunes and warm lacking in Rhipiphorus (Rhipiphorini). mountain slopes. Northern populations may The triungulins of M. ferrugineum and M. survive when suitable climatic conditions are tricuspidatum are very similar. The main dif¬ met. It is possible that Macrosiagon species ferences given by Chobaut (1891, 1906b) are disperse from their dry and warm Mediterra¬ that the head of M. tricuspidatum is consider¬ nean habitat to other arid zones where po¬ ably smaller and that the anterior edge is much tential hosts are present. Macrosiagon tricus¬ more rounded than in M. ferrugineum. The pidatum specimens were collected in the eighth and ninth abdominal segments are also Hungarian puszta (NNM, ITZ). Other arid shorter and the edges of the three thoracic ter- zones are present along railway tracks gites are much more rounded in M. tricuspida¬ throughout Europe suggesting a possibility tum than in M. ferrugineum. These differences how Macrosiagon species may have come are clear, although the triungulins are poorly il¬ even that far north. However, we do not think lustrated and the chaetotaxy of both species is that rhipiphorids disperse easily over large not described. Grandi (1936) illustrated the distances in one generation. The adult beetles triungulin of M. ferrugineum and gives a more do not eat, are short-lived and were only kept precise description than the previous papers. alive for a maximum of 8 days in captivity Except for the total body length of the living (Chobaut, 1891). Adult beetles are also poor triungulin (0.5 mm.) no other anatomical flyers. The dispersal of triungulins depends on measurements are given. The triungulins pre¬ the activities of carrier hosts, which will not sented in figs 1-4 are very similar in almost all move far from their nest(s). Ent. Ber., Amst. 54 (1994) 209

Macrosiagon beetles as well as their triun- 1985). In Westervoort at least five different gulins are usually found on flowers, e.g. Eryn- species were listed and recently, gium campestre L., E. maritimum L. and the larger Eumenes papillarius (Christ) was Solidago spec. (Chobaut, 1891, 1906b, Bal- found (Smit, 1991; Smit, unpublished). The oc¬ duf, 1935; A.P.J.A. Teunissen, personal com¬ currence of a triungulin on the sphecid Nitela munication). Both E. campestre and S. cana¬ borealis (table 1) may indicate that the beetle densis L. are present at the railway siding in may use an even broader range of hosts includ¬ Westervoort (Smit, 1991). Triungulins sit and ing the subfamilies Larrinae and Pemphredoni- wait in flowers for an opportunity to cling to a nae (Sphecidae), most of which have their nests visiting insect. This behaviour allows them to in hollow stems or twigs (Lomholdt, 1975). encounter a variety of flying insects. However, we wonder whether the small Nitela Triungulins do not seem to distinguish the borealis (3.5-4 mm) is large enough to be a suit¬ sex of a carrier host (table 1; Linsley et al., able host for Macrosiagon. 1952; Tomlin & Miller, 1989). If they board a This is the first time that Chrysididae have male they might never come to a nest with lar¬ been observed as carrier hosts in nature. vae. It is suggested that Rhipiphorus (smithi) Balduf (1935) previously referred to an ex¬ triungulins on halictid bees may get a second periment done by Cros who collected triungu¬ chance changing from male to a hibernating lin larvae of M. tricuspidatum from flowers female host during a copulation (Tomlin & and observed that they dinged to a variety of Miller, 1989). Copulatory sessions of these hymenopteran hosts including Chrysis, Osmia bees often occur in their underground burrows bees, Polistes and Eumenes wasps offered in and last some minutes. However, copulation captivity. In this experiment it was found that in wasps often takes less than one minute. 12 triungulins adhered to one Eumenes wasp. Females usually mate only once in their life The use of Chrysididae as carriers will un¬ time. So, it is unlikely that a triungulin ever doubtedly contribute to both the dispersal and gets the opportunity to give up its firm grip the survival of triungulins (table 1). Both and exchange carrier host. Chrysis angustula and Trichrysis cyanea visit Macrosiagon species use a broad spectrum of a number of different twig nesting Eumenidae, different eumenid host species, including the Sphecidae (Pemphredoninae, Larrinae) and large Mediterranean wasp Rhynchium oculatum sometimes solitary bees (Morgan, 1984). By (14.5-18 mm) and the more slender and smaller using Chrysididae, the triungulin will have the Eumenes (14-16 mm), Euodynerus and Sym- opportunity to be transported to several differ¬ morphus (9-13 mm) species (Chobaut, 1891; ent host species. Moreover, clinging to a fe¬ Bétis, 1912; Balduf, 1935; Grandi, 1936). male chrysidid may avoid the risk that a car¬ Indeed, the highly variable body size of the ex¬ rier will not get offspring, while the chrysidid amined beetles indicates that different wasp spe¬ wasp prefers to enter the nests of successful cies are used as hosts between and within differ¬ wasps only. It is also possible that a triungulin ent populations. It is possible that the range of uses a chrysidid larva itself as host after the suitable hosts extends far over the species that latter has destroyed the legitimate cell owner. are previously mentioned for the Mediterranean Using chrysidid wasps as carriers may, how¬ region. A broad range of host species will in¬ ever, incur disadvantages, because the triun¬ crease the probability to establish in an invaded gulin and the developing chrysidid larva may area, but also facilitates dispersal activities. have to compete for food when both feeding Rhynchium oculatum is absent in The Nether¬ simultaneously on the same host larva. lands, but two Euodynerus and four Eumenes Nothing is known about the outcome of a con¬ species are known from the Dutch fauna. Other test between triungulins and a chrysidid larva solitary eumenids, such as Symmorphus and nor that between two or more solitary living Ancistrocerus with 8 and 12 Dutch species re¬ triungulins. The record of two or more triun¬ spectively, are much more common (Hensen, gulins on one carrier is not uncommon (table 210 Ent. Ber., Amst. 54 (1994)

1; Balduf, 1935; Tomlin & Miller, 1989). So, in northern regions is able to hibernate as dia- more than one triungulin may be introduced in pausing triungulin outside a nest, becoming ac¬ a nest at once. Grandi (1936) found that 1 to 4 tive next spring to find a carrier similar to larvae of M. ferrugineum developed from the Metoecus paradoxus. Metoecus is thought to four examined nests of Rhynchium oculatum, have always one generation per year like its host whereas every nest also produced at least one Vespula vulgaris, since adult beetles were never new wasp. More spectacular is a record of taken early in the season. Metoecus paradoxus more than 50 Metoecus paradoxus beetles in a emerges and deposits the eggs from late July un¬ nest of Vespula vulgaris by S. C. Langeveld til early October (Hoffer, 1883). The diapausing (unpublished). In the Rhipiphorinae one single triungulin is thought to survive for more than 8 beetle develops per nest cell. Triungulins of months in their egg shell (Chapman, 1891). The Rhipidius pectinicornis are the only faculta¬ life cycle of M. paradoxus is similar to another tively gregarious rhipiphorids known: 1 or 2 northern species of Rhipiphorus from Canada of and sometimes even 5 beetle larvae may de¬ which the triungulins hibernate attached to the velop in one cockroach under natural circum¬ wing of diapausing female bees (Tomlin & stances (Stamm, 1936; Barbier, 1947). Miller, 1989). Southern Macrosiagon popula¬ The life cycle and the number of generations tions may have more than one generation per of many Rhipiphorinae are insufficiently year and adapt the number of generations to that known. Our record of Macrosiagon triungulins of their hosts. The presence of the beetles during as early as June 1, 1990 is the earliest observa¬ the entire summer period supports the idea that tion known so far. Our records of July 2, 1991 they do not belong to a single cohort. The adult can also be rated among the early observations. beetles of M. praeustum, for example, have In Pisa (Italy) the triungulin and mature larvae been collected near Zaragoza (northern Spain) of M. ferrugineum were found in Rhynchium as early as May 26 and 28, 1958 (NNM). On the nests in the second half of July and early August other hand, an adult beetle of M. ferrugineum (Grandi, 1936). In southern France Chobaut has been captured in Policoro (South Italy) as (1891) observed M. ferrugineum laying the eggs late as October 7, 1977 (NNM). More know¬ in July and the emerged triungulins in August. ledge about the rhipiphorid life cycle may lead Triungulins of Rhipiphorus subdipterus were to more observations of these rarely collected collected in early August and those of M. tricus- beetles and to a better understanding of their pidatum as late as August 26 (Chobaut, 1906a, geographical distribution and life history. b). Unfortunately, the possible presence of Ma¬ crosiagon triungulins or adult beetles in Acknowledgements Westervoort could not be established in late summer as the frequency of sampling then was The authors wish to thank Jan Krikken and Kees van less intensive. Balduf (1935) postulates that the Achterberg (National Museum of Natural History), Jacques van Alphen, Ian Hardy and Jan Sevenster (IEEW, appearance of triungulins coincides with the pe¬ University of Leiden) for helpful discussions and com¬ riod that the carrier wasps have mature larvae. ments on the manuscript. Both Macrosiagon pectinatum (Fabricius) in We are grateful to B.J.H. Brugge and W. Hogenes Indiana and Rhipiphorus solidaginis (Pierce) in (ZMA), A. van Assen (NNM), A.P.J.A. Teunissen, P. Poot and C.J.M. Berger for enabling us to use data from Nebraska (USA) hibernate as mature larva, pu¬ their collections and field observations. pate the following spring and emerge as adults Wijnand Takkenberg of The Department of Molecular in July. A similar seasonal distribution of stages Cell Biology of The University of Amsterdam is thanked has been demonstrated in Mediterranean for enabling us to use a scanning electron microscope Macrosiagon ferrugineum: the larvae hibernate (SEM) and assisting with making photographs. and pupation has been observed in June. The postulated life cycle is, however, inconsistent References with our earliest record of Macrosiagon triun¬ Balduf, W.V., 1935. The bionomics of entomophagous gulins on June 1. It is possible that Macrosiagon Coleoptera: 1-220. John S. Swift, St. Louis. Ent. Ber.. Amst. 54 (1994) 211

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