Survey of first instars of the Siphonini (Diptera: )

JAMES E. O'HARA

First instars of 68 speciesof the Siphoniniwere examined, includingrepresentatives of all gen- era of the tribe except Proceromyia Mesnil, and all subgenera of Meigen except Uruactia Townsend.Two aspectsof first instar siphoninesare markedlyvaried: features of the cephalopharyngealskeleton and vestiture ventrally on posterior abdominal segments. These regions of first instars are described for the examined genera and subgenera of the Siphonini, in addition to four groups of undescribed,New World species of Siphonas.l. unplaced to sub- genus. The phylogeneticsignificance of particular character states of first instar siphonines is discussed.

James E. O'Hara, Department of Entomology, University of Alberta, Edmonton, Alberta, Canada T6G 2E3.

INTRODUCTION least 200 undescribed species (O'Hara 1987). An- dersen the first characterization Tachinid are of other (1983) provided parasitoids , of first instars of the but fewer than ten almost other their three Siphonini, exclusively , during were known from first instars at larval instars. Due to this tachinid siphonine species parasitic habit, that time. larvae are not collected or described. commonly Due to the relative of form dead females of tachinids constancy among However, larviparous first instar and illustra- often have first instars in their ab- siphonines, descriptions fully developed tions contained herein are restricted to two re- and these can be extracted and domens, prepared of first instars the most for from dried or gions displaying morpho- study alcohol-preserved speci- variation: the skeleton mens. First instars a suite of taxonomi- logical cephalopharyngeal provide and vestiture on the abdominal useful and the ventrally posterior cally characters, permit descrip- These are described from classification and of segments. regions rep- tion, phylogenetic analysis resentatives of most of the 15 and taxa based on two life of different form genera subgen- stages very era of the O'Hara and structure. Siphonini recognized by (1987). Where possible, character states of first instars are First instars of larviparous tachinids were discussed in a phylogenetic context. routinely described by Thompson (e.g., 1923 and his series on "The Tachinids of Trinidad"), but sel- dom described by other workers until recently. MATERIALS AND METHODS in a series of four devotcd Beginning 1976, papers Materials to the description of first instar tachinids of the USSR fauna has been published (Farinets 1976, This study is based on examination of first instars 1980; Richter & Farinets 1983, 1986). Though our of 68 species of the Siphonini. Specimens exam- knowledge about first instars of the Tachinidae is ined were dissected from dried, pinned, adult slowly improving, they are still very inadequately females housed in the following collections (full studied. addresses and names of curators are given in First instars of the Siphonini are treated in this O'Hara 1987): BMNH, British Museum (Natural paper. The tribe is cosmopolitan in distribution, History), London, England; CAS, California with about 300 described species and probably at Academy of Sciences, San Francisco, California, 368

USA; CNC, [Canadian National Collection] cited in the text by a one-letter color code (B, Biosystematics Research Centre, Ottawa, On- blue; G, green; 0, orange; R, red; W, white; Y, tario, Canada; DPI, Department of Primary In- yellow) followed by a dissection number (e.g. dustries, Indooroopilly, Queensland, Australia; R77-dissection 77 in red scries). JEOH, private collection of the author; MCZ, First instars were examined with a Leitz SM- Museum of Comparative Zoology, Cambridge, LUX compound microscope at magnifications up Massachusetts, USA; MSU, Michigan State Uni- to 400X. Illustrations were made with the aid of a versity, East Lansing, Michigan, USA; PHA, pri- Leitz drawing tube. Illustrations in this work are vate collection of P. H. Arnaud, Jr., c/o CAS; cited in the text as "Fig.", those referenced from UCB, University of California, Berkeley, Califor- other works are cited as "fig.". nia, USA; USNM, United States National Museu Muscum, Washington, D.C., USA; USP, Classification of the Siphonini de Zoologia, Universidad de Sao Paulo, Sao Paulo, Brazil; WLD, private collection of W. L. The classification of the Siphonini followed here is Downes, c/o MSU; WSUP, Washington State that of O'Hara (1987). Seven genera are recog- University, Pullman, Washington, USA; ZMUC, nized in the tribe: Brauer & Bergen- Zoologisk Museum, Copenhagen, Denmark. stamm, Proceromyia Mesnil, Lioy, Robineau-Desvoidy, Robineau- Desvoidy, Robineau-Desvoidy and and instars Preparation storage of first Siphona Meigen. First instars were examined Approximately 30 % of adult female siphonines from representatives of all genera except Pro- dissected by O'Hara (1987) containcd fully de- ceromyia. Two distinct, possibly monophyletic, veloped first instars. These were removed from lineages of Ceromya were recognized by O'Hara dried specimens of adult females and prepared for (1987) and treated separately: Ceromya s.str. and examination and storage as follows. The abdomen the C. silacea species group-these lineages are of an adult female siphonine was detached from also treated separately here. Nine subgenera are the thorax and partially cleared in 10 % NaOH. recognized in Siphona s.l. , all reduced from gener- While still in the NaOH solution, the genitalia ic status by O'Hara (1987): Actinocrocuta were dissected out and the abdominal cavity ex- Townsend, Aphantorhapha Townsend, Aphan- amined. First instars, if present, were carefully torhaphopsis Townsend (previously called teased from the abdomen and allowed to clear to Asiphona Mesnil, and comprising a polyphyletic a nearly transparent state. Genitalia were then assemblage of Old World species not assignable to prepared for storage in glycerine, and the abdo- other subgenera), Baeomyia O'Hara, men reattached to the adult specimen, by the Robineau-Desvoidy, Pseudosiphona Townsend, methods outlined in O'Hara (1983: 271-2). Once Siphona Meigen, Siphonopsis Townsend and larvae were sufficiently cleared, the NaOH solu- Uruactia Townsend. First instars were examined tion was replaced with several washes of distilled from representatives of all Siphona subgenera ex- water. Larvae were next transferred to a watch cept the last. Examined first instars of undescribed glass containing a 10 % solution of glycerine. By New World Siphona species not belonging to a allowing the water to slowly evaporate from the named subgenus are designated in the text as un- glycerine solution (usually requiring a couple of placed or are assigned to one of three numbered days), larvae generally absorbed glycerine at a species groups, following O'Hara (1987). slow enough rate to prevent collapse or distortion of their extremely delicate exoskeleton. DESCRIPTIONS Larvae were stored for in in study glycerine General remarks genitalic dishes along with the female genitalia, and identified by colored and numbered tags kept First instars of the Siphonini are elongate and ver- with both adult specimen and genitalia/larvae. miform, with 12 apparent segments (Fig. 1). The These dissection tags remained with the speci- anteriormost segment is termed the cephalic seg- mens upon return of borrowed material, to pro- ment, and the next 11are numbered consecutively vide a permanent record of the specimens upon from the anterior end as thoracic segments 1-3 which this study is based. These dissections are and abdominal segments 1-8 (Fig. 1).