Caribbean Journal of Science, Vol. 40, No. 1, 52-61, 2004 Copyright 2004 College of Arts and Sciences University of Puerto Rico, Mayagu¨ez Review of the Biology of Melittobia acasta (Walker) (Hymenoptera: Eulophidae) and Additions on Development and Sex Ratio of the Species JORGE M. GONZÁLEZ1,JORGE B. TERÁN2 AND ROBERT W. MATTHEWS1 1University of Georgia, Department of Entomology, Athens, Georgia 30602, USA 2Universidad Central de Venezuela, Facultad de Agronomı´a, Instituto de Zoologı´a Agrı´cola, Apdo. 4579, Maracay, Aragua, Venezuela. Corresponding author: [email protected] ABSTRACT.—A list of known hosts of Melittobia acasta and different biological aspects presented in previous literature are summarized and clarified. Development, sex ratio, and offspring production, on wild, facultative, and factitious hosts, and size of stages at different temperatures are shown. In general, devel- opment time is equivalent and similar to that of other Melittobia species; however, as temperature rises development time decreases. Sex ratio oscillates between 96 to 98% female depending on the host, falling into the expected percentage for most species in the genus. Total offspring numbers were similar to those produced by other Melittobia species using the same hosts. KEYWORDS.—development, sex ratio, offspring production INTRODUCTION bus, and honeybees (Apis mellifera), some re- search has targeted control aspects (Alford Melittobia wasps are gregarious ectopara- 1975; Dahms 1984b; Doroshina 1990; Erick- sitoids of wasps and bees especially of son & Medenwald 1979; Farkas & Szalay those that build mud nests. Before Dahms’ 1985; Fye 1965; Herting 1977; Holm 1960; (1984a) revision, the genus consisted of one Holm & Skou 1972; Husband & Brown species native to Europe (M. acasta), two 1976; Jelinski & Wojtowski 1984; Kalinin & native to North America (M. chalybii and M. Molchanov 1987; MacFarlane & Donovan megachilis), and a few others from Australia 1989; MacFarlane & Griffin 1994; MacFar- and eastern Asia. After this revision the lane & Palma 1987; MacFarlane et al. 1994; number of species increased to 14 world- Maeta 1978, 1985, 1999; Packard 1864; Pou- wide. Although M. acasta remained the vreau 1973; Santis 1981; Schmid-Hempel only European species, Dahms also re- 1998, 2001; Smith 1853; Stolvov & Palevich corded it from Canada, Japan, New Zeal- 1988; Thompson 1946; Torchio 1963; and, and South America. For North Valkeila 1959; Wael et al. 1993, 1995; Zerova America, species increased to eight, includ- et al. 1986). ing M. acasta. Other studies emphasized, evolutionary, Prior to Dahms’ work, for U.S. species morphological, biological and behavioral the name mostly used in the literature was aspects, especially those related to court- M. chalybii, but these identifications were ship, with M. acasta serving as a model or often erroneous, and as many as 4 species compared with other species (Altson 1920; were confused as one (Gonza´lez and Mat- Assem 1975, 1976a, 1976b, 1985; Assem & thews 2002). Likewise, some confusion ex- Maeta 1978; Assem et al. 1982; Balfour- ists for records of M. acasta. Browne 1922; Borgia 1980; Dahms 1984b; Melittobia acasta is reported as a parasite Doroshina 1989; Gonza´lez 1994a, 1994b; or hyperparasite of members of various or- Gonza´lez & Matthews 2002; Gonza´lez & ders, including Hymenoptera, Diptera, Tera´n 2001; Gonza´lez et al. 1996, 1999, 2004; Lepidoptera and Coleoptera (Table 1). Be- Klunker & Fabritius 1992; Lapp 1994; Lith cause it sometimes also attacks bees used 1955; Malyshev 1968; Nong & Sailer 1986; for crop pollination such as Megachile, Bom- Parker & Thompson 1928; Picard 1922, 52 MELITTOBIA ACASTA (HYMENOPTERA) 53 TABLE 1. Reported hosts of Melittobia acasta (Walker) Host group Countries Reference Social Bees (Bombus spp.; Apis Great Britain; New Zealand Alford 1975; Balfour-Browne 1922; spp.) Erickson & Medenwald 1979; Hobbs & Krunic 1971; MacFarlane & Donovan 1989; MacFarlane et al. 1994; Valkeila 1959; Wael et al. 1993, 1995 Parasitic Bees (Psythirus spp., Great Britain; Germany Alford 1975; Wolff & Krausse 1922 Stelis spp.) Solitary Bees (Anthophora spp., Great Britain; Russia; USA; New Balfour-Browne 1922; Doroshina Chalicodoma sp., Heriades spp.; Zealand; Japan; Finland 1989, 1990; Farkas & Szalay Anthidium sp.; Megachile spp.; 1985; Herting 1977; Holm & Osmia spp.) Skou 1972; MacFarlane & Donovan 1989; Maeta 1985; Smith 1853; Thompson 1950a; Valkeila 1959 Mud dauber wasps (Trypoxylon Great Britain; Cuba; Venezuela; Balfour-Browne 1922; Dahms spp., Sceliphron spp.) Japan 1984b; Gonza´lez 1994a, 1994b; Gonza´lez & Tera´n 1996; Gonza´lez et al 2004; Maeta 1985 Parasitic wasps (Alysia Great Britain; Japan; New Altson 1920; Balfour-Browne 1922; manducator; Monodontomerus Zealand; Germany Dahms 1984b; Donovan 1989; spp.; Sinophorus turionus; Maeta & Yamane 1974; Wolff & Sphecophaga vesparum, Chrysis Krausse 1921, 1922; Husain & spp.) Khan 1986; Thompson 1950a Other solitary wasps Germany; Finland Herting 1977; Lith 1955; Wolff & (Ancistrocerus spp., Odynerus Krausse 1922; Malyshev 1911, spp. 1968 Social wasps Great Britain; Japan Bouc˘ek 1959; Maeta 1985; Maeta & Yamane 1974 Flies and parasitic flies (Musca Great Britain; Japan Dahms 1984b; Graham-Smith spp.; Neobellieria spp.; 1916, 1919; Herting 1978; Maeta Sarcophaga spp.; Calliphora & Yamane 1974; Waterston 1917 spp.; Anthrax spp.; Metagonistylum minense; Paratheresia claripalpis) Lepidoptera Great Britain Herting 1975; Morley & Rai; Thompson 1950b Coleoptera Czechoslovakia Bouc˘ek 1959 1923; Schmid-Hempel 1998, 2001; Ranger ing species identity in Melittobia. Results 1996). will help to promote nomenclatural stabil- Lists of synonymies of M. acasta are in ity and thereby facilitate future work on Boucˇek & Graham (1978a, 1978b); Dalla this interesting genus. Here we focus on the Torre (1898); Dahms (1984a); Domenichini widespread M. acasta. (1966); Hansson (1991); Holm (1960); Kalina (1989); Kostjukov (1978); La Salle (1993); Peck (1963); and Schmiedeknecht (1909). MATERIALS AND METHODS Through careful reading of the older pri- mary literature coupled with study of mu- In order to compare the status, distribu- seum voucher materials and controlled tion, and other aspects related to the biol- laboratory studies, we are attempting to ogy of M. acasta, a thorough literature re- untangle some of the confusion surround- view was done. Laboratory studies were 54 J. M. GONZA´ LEZ, ET AL. initiated using M. acasta originally collected All experiments using S. fistularium as in Venezuela (Assays 1-4) or California, hosts were conducted in climatically con- U.S.A. (Assay 4). Unless otherwise noted, trolled chambers at Instituto de Zoolog´ıa cultures were established in 2-dram vials Agr´ıcola, Universidad Central de Venezu- and maintained at 25°C and 70% RH. ela, Maracay, Venezuela. Experiments with Assay 1: In order to see if hosts [Sceliph- other hosts (assay 4) were done in incuba- ron fistularium (Hymenoptera: Sphecidae)] tors at University of Georgia, Athens, Geor- could survive and develop if parasitoids gia, U.S.A. were removed, individual mated females of M. acasta were allowed to lay about 100 eggs/host (n=100). Females were then re- RESULTS moved and a few days later developing third instar M. acasta larvae were removed Although some authors (Eickwort 1971, from every host. 1973; Hobbs & Krunic 1971; Holm 1960; Assay 2: To assess whether temperature Husband & Brown 1976; MacFarlane & had any influence on size, regular cultures Pengelly 1977; Maeta & Yamane 1974; were established on S. fistularium at differ- Newport 1849a, 1849b, 1852a, 1852b, 1853; ent temperatures (15°,20°,25°,30°, and Packard 1864; Spradbery 1973; Thomson 35°C) and 70% RH. Length and width of 1878; Wolff & Krausse 1921) mentioned eggs, all larval instars, and pupae were Melittobia or related species in their work, measured of a sample from the whole off- after careful analysis of those works and spring produced (Brood size approxi- available voucher specimens we conclude mately 400-500 individuals per host; that they were often working on (or found) Sample size: n=39 for each stage and tem- M. acasta (Dahms 1984a; Gonza´lez & Mat- perature). Egg widths were measured at thews 2002). two places (small and large width) because When females of M. acasta are presented of their “pear like” shape. Larval width was with a suitable host (i.e., Sceliphron spp., measured at the mid part of the body, and Trypoxylon spp.), they wander around it, pupae were measured at the junction of the and after some time spent (1-48 h) “assess- thorax and abdomen. Measurements were ing” the host, they puncture the host’s exo- taken using a stereoscope adapted with an cuticle with their ovipositor. After a few ocular micrometer. seconds, hemolymph starts to ooze from Assay 3: To study duration of each life the wound, upon which the female then stage and instar of M. acasta, parasitized S. feeds. fistularium hosts were maintained at vari- Females become distinctly physogastric ous temperatures (15°,20°,25°,30°, and 12-48 hours after first feeding. Beginning 12 35°C) and 70% RH (n=20/ each tempera- to 24 hours after feeding, most females start ture). Observations were made every 12 laying eggs (Table 2). Eggs are coated with hours and the developmental stage was re- a sticky substance that allows them to ad- corded. Sample individuals were removed here to the host and to other eggs. Eggs are (see assay 2) for measurements and to de- normally laid in batches of 4 to 12, however termine if they