© Entomologica Fennica. 8 July 1997 Parasitism of Sty/ops(Strepsiptera, Stylopidae) in poly- and oligolectic Andrena hosts (Hymenoptera, Apoidea) Antti Pekkarinen Pekkarinen, A. 1997: Parasitism of Sty lops (Strepsiptera, Sty1opidae) in poly­ and oligolectic Andrena hosts (Hymenoptera, Apoidea). - Entomol. Fennica 8: 109-111. The taxonomic status of many Sty lops species described often on the basis of poor female characters is problematic and host specifity of these dubious species is largely unsettled. In Germany and Finland, oligolectic Andrena species were not observed to be parasitized more frequently by Stylops than polylectic ones. The result does not support several coexisting Stylops species with strict host specifity. Antti Pekkarinen, Department of Ecology and Systematics, P. 0. Box 17, FIN-00014 University of Helsinki, Finland Received 25 August 1996, accepted 21 May 1997 1. Introduction ever, Kinzel bach ( 1978) stressed that western Palae­ arctic Stylops populations are in no way a homo­ Strepsiptera are endoparasites of other insects. The geneous group and that great variation exists in males are free living and winged, while females the structures of female cephalothorax, and in the are wingless and, except in one family, also leg­ form of aedeagi in the males. Furthermore, Kinzel­ less and do not leave the host. Stylops species are bach (1978) noted some kind of similarity in the parasites of many species ofAndrena. Species de­ morphology of Stylops parasitizing species of the limitation of parasites is problematic when popula­ same subgenus of Andrena, but he left the taxonomic tions on different hosts are slightly different (Mayr value of this variation unsettled. & Ashlock 1991), and a great number of Stylops Host specificity of Stylops species is suggested species have been described on the basis of poor to vary from one to several species of hosts. Bohart characters in female cephalothorax (e.g. Luna de (1941) noted 21 "distinctive" species of Stylops Carvalho 1974, Kifune & Hirashima 1985, Ki­ from North America, about half of them having fune & Maeta 1990). The morphology of males is only one host species. In California, Linsley and much more suitable for taxonomic comparisons MacSwain ( 1957) reported that S. pacifica Bohart than the few structures visible on the females. is a common parasite of two Andrena species, but However, males have been found quite rarely and is unable to complete its life cycle on other host males of most described species are unknown. bees. In Germany, Borchert (1963) found that 1st Kinzelbach (1978) listed 55 described species instar larvae (triungulins) of Stylops parasitizing of Sty lops and 161 species of Andrena as hosts of A. vaga differed in their morphology from the lar­ Stylops from the western Palaearctic area, but he vae parasitizing three other vernal Andrena spe­ preliminarily regarded all the described species cies. This led him to suggest that there were two as synonyms of Stylops melittae Kirby, 1802. How- different species of Stylops in question. 110 Pekkarinen: Parasitism of Sty lops in Andrena hosts • ENTOMOL. FENNICA Vol. 8 As is generally the case in Strepsiptera, the lectic Andrena vaga Panzer in North Zealand in life cycle of Stylops involves hypermetamorpho­ Denmark. In Finland, stylopids have been record­ sis. A female produces even several thousand free­ ed on polylectic and oligolectic Andrena species living 1st instar larvae (Linsley & MacSwain (in collection materials) as follows (Pekkarinen 1957), which the parasitised host bee leaves on & Raatikainen 1973): food flowers of other bees. If a Stylops species is Species Specimens Specimens Percentage host specific, then a critical point during its life studied stylopized stylopized cycle would be to find the right host among sev­ Polylectic 5 2247 97 4.3 eral bee species visiting flowers with the 1st in star Oligolectic 6 2713 50 1.8 larvae. The degree of flower specialization, espe­ The frequency of stylopized specimens is sig­ cially in pollen collecting, varies among bees. Oli­ nificantly smaller on oligolectic species (X2 = 25.4, golectic bee species collect pollen within a few P < 0.001). This result indicates that oligolectic species of a genus or a family of plants, whereas Andrena species are not stylopized more fre­ polylectic species collect pollen from plants be­ quently than polylectic ones, and thus do not sup­ longing to two or several families. Even though port several coexisting Stylops species with strict oligolectic bees usually forage for nectar from host specifity. If the same Sty lops species parasi­ various kinds of flowers, the number of all food tizes both oligo- and polylectic hosts, the large flowers is for oligoleges apparently much lower flower spectrum of polyleges possibly favours the than for polyleges. For instance, Elfving (1968) dispersal of the 1st instars and the whole life cy­ recorded from Finland on an average(± SD) 14.9 ± cle of Stylops better, than the lower spectrum of 10.4 and 31.7 ± 21.8 food plants for 13 oligo- and oligoleges. 12 polylectic and widely distributedAndrena spe­ cies, respectively. Presumably, the successful completion of the life cycle of host specific Sty lops Table 1. Numbers non-stylopized and stylopized (Sty­ lops infested) on polylected (Pol.) and oligolectic (OJ.) is better in species parasitizing oligolectic hosts species of Andrena recorded in Finland and the former than in those parasitizing polylectic hosts. The aim Western Germany. The material according to Pekkari­ of this report is to find if oligolectic Andrena spe­ nen and Raatikainen (1973), Kinzelbach (1978), West­ cies are more often infested by Sty lops (stylopized) rich (1990), Pekkarinen (1997) and unpublished notes than polylectic ones, and by this means elucidate by the late E. Valkeila. the host specifity of this group which has been Finland Germany problematic. Pol. 01. I %ol. Pol. 01. I %ol. Non-sty!. 12 11 23 48 25 29 54 54 2. Results and conclusions Sty I. 6 7 13 54 32 21 53 40 I 18 18 36 50 57 50 107 47 About half of all Andrena species in Finland and % styl. 33 39 36 54 42 49 Germany are oligolectic, and among the species in which stylopization has been observed the propor­ Acknowledgements. Some records on stylopization tions are 54 and 40 percent, respectively (Table 1). originate from unpublished notes by the late Erkki Valkeila. In Finland, stylopids have been recorded on about The notes are preserved in the Department of Applied Zo­ one third of the polylectic as well on the oligolectic ology of the University of Helsinki. An unknown referee species. The same proportions are higher in Ger­ made several useful corrections to the manuscript. many, especially in polylectic species. However, the higher proportion may be simply caused by the larger material of Andrena from Germany, and References the smaller material from Finland possibly does not include all rarely stylopized species. Bohart, R. 1941: A revision of the Strepsiptera with special reference to the species of North America. - Univ. Local proportions of stylopization may be Calif. Pub!. Entomol. 7: 91-160. highly variable, and Jensen (1971) noted even 18% Borchert, H.-M. 1963: Vergleichend morphologische Unter­ stylopized specimens in a large colony of oligo- suchungen an Berliner Stylops-Ll (Strepsipt.) zwecks ENTOMOL. FENNICA Vol. 8 • Pekkarinen: Parasitism of Stylops in Andrena hosts 111 Entscheidung der heiden Spezifitatsfragen: I. gibt es (Studies on the Japanese Strepsiptera XIII).- Esakia, an unseren Frtihjahrs-Andrenen (Hymenopt., Apidae) Spec. Issue 1: 97-110. mehrere Stylops-Arten und 2. gibt es WirtsspezifiUiten? Kinzelbach, K . 1978: Insecta Facherfliigler (Strepsiptera). -Zoo!. Beitr. N. F. 8:331-445. -In: Tierwe1t Deutschlands 65: 1-166. Veb Gustav Elfving, R. 1968: Die Bienen Finn lands.- Fauna Fennica Fischer Verlag, Jena. 21: 1-69. Linsley, E. G. & MacSwain, J. W. 1957: Observations on Jensen, 0. 1971: Iagtagelser over en koloni af stylopisered the habits of Stylops pacifica Bohart. - Univ. Calif. bier, And rena vaga Panz., i Nordsjreland (Strepsiptera Pub!. Entomol. II: 395-430. & Hymenoptera, Apidae). (Observations on a colony Luna de Carvalho, E. 1974: Contribuicao parao estudo dos of stylopized Andrena vaga Panz. in North Zealand.) Sty lops da Peninsula Iberica (Steep. Stylopidae).-Eos­ - Entomol. Medd. 39: 90-95. (In Danish, with Eng­ Rev. Esp. Entomol. 48(1972): 301-365. lish summary.) Mayr, E. & Ashlock, P. 1991: Principles of systematic zool­ Kifune, T. & Hirashima, Y. 1985: Nine new species of the ogy. 2nd ed. -McGraw Hill, Inc., New York. 475 pp. genus Stylops (Strepsiptera: Stylopidae) parasitic on Pekkarinen, A. 1997: Oligolectic bee species (Hymenop­ the genus Andrena (Hymenoptera: Andrenidae) of Ja­ tera: Apoidea) in northern Europe.-Entomol. Fennica pan (Studies on the Japanese Strepsiptera X).-Esakia 8. (In print.) 23: 45-57. Pekkarinen, A. & Raatikainen, M. 1973: Strepsiptera of Kifune, T. & Maeta, Y. 1990: Ten new species of the genus Eastern Fennoscandia.- Not. Entomol. 53: 1-10. Stylops (Strepsiptera, Stylopidae) parasitic on the ge­ Westrich, P. 1990: Die Wildbienen Baden-Wiirttembergs nus Andrena (Hymenoptera, Andrenidae) of Japan 1-11. 2nd ed. - Verlag Eugen Ulmer, Stuttgart. 972 pp. .