Petilium Townes, 1970

Taxonomic History / Nomenclature
Petilium Townes, 1970. Type species: Petilium tibiale Townes, 1970. Original designation.
Remarks
Only two species are known as of 2015:

Petilium palliventre Townes, 1970
Petilium tibiale Townes, 1970

The following label data are given by Townes (1970) for the type series of Petilium tibiale:
Holotype: female, Lafuna Amarga, Natales, Magallanes, Chile, Dec. 14 to 21, 1960, Luis Pena (AEI).

Paratypes:
3 Males, same data as type (AEI).
2 Males, Rubens, Punta Arenas, Magallanes, Chile, Dec. 13, 1950, Luis Pena (AEI).
Male, Lago Frio, Cayhaique, Magallanes, Chile, Dec. 11, 1960, T. Cekalovick (AEI).
Male, La Pensula, Magallanes, Chile, Dec. 11, 1960, T. Cekalovick (AEI).
4 Females, Las Cabras, 1500m., Chile, Jan 6 to 31, 1963, Luis Pena (AEI).
Female, Lago Futalaufquen, Chile, Jan. 24, 1968, L. and J, Strange (AEI).
Female, Pichinahuel, Cordillera Nahuelbuta, Arauco, Chile, Jan. 1 to 10, 1959, Luis Pena (CNC).

Diagnosis and Relationships
The two species initially included in Petilium by Townes (1970) are remarkably different from one another in such features and the presence or absence of propodeal carinae and the glymma, yet are otherwise very similar in such features as wing venation, clypeal, mandibular, and ovipositor morphology, and thoracic sculpture.

The combination of a short, broad fore wing stigma, relatively slender mandibles with long ventral tooth, relatively long, slender, straight ovipositor, long, relatively slender T1, and epicnemial carina not extending to anterior margin of mesopleuron serve to differentiate Petilium from other pionines. Specifically, the shape of the mandible separates tibiale from Syntactus and other genera that lack a glymma, while the slender T1 and position of the epicnemial carina separates Petilium from other pionine genera. The huge, u-shaped groove laterally between propodeum and metathorax and the slender ovipositor solidify the inclusion of Petilium in Pionini as the latter is currently characterized.

Description
Clypeus with surface more or less uniformly setose and punctate (Fig. 3); ventral margin evenly convex, the margin blunt but not broadly so (Fig. 3); epistomal sulcus impressed throughout, though broad and weaker medially; clypeus in profile not or only weakly protruding. Face setose, coarsely to finely punctate medially; inner eye margins parallel or nearly so (Fig. 3). Malar space short but distinct, about 0.5-0.7 times basal width of mandible; malar sulcus absent. Mandible (Fig. 3) broad, distinctly narrowing from base to apex, without basal depression in type species, but with shallow depression in P. palliventre_; dorsal tooth distinctly narrower and much shorter than ventral tooth; ventral margin distinctly carinate. Maxillary palp a little shorter than height of head; female antenna slightly shorter than body; about equal in length to body in male. Hypostomal carina meeting occipital carina well above base of mandible; occipital carina complete. Epomia present. Epicnemial carina not reaching anterior margin of mesopleuron (Fig. 5), though almost so in one of four specimens examined. Notaulus sharply impressed on anterior declivity, varying from absent on disk (tibiale_) to long but very shallowly impressed and barely indicated (palliventre). Groove between propodeum and metapleuron exceptionally large, very broadly u-shaped, readily visible in lateral view; broad, u-shaped groove mid-dorsally between propodeum and metanotum also readily visible in lateral view in females, more v-shpaed in the one male examined (as in Fig. 5); pleural carina well-developed, complete; propodeal carinae absent in palliventre, complete in _tibiale-, with median and lateral longitudinal carinae as well as anterior and posterior transverse carinae uninterrupted, areola completely delimited. Hind femur slender, as in Fig. 1; apical margin of mid tibia expanded as a tooth that is much weaker than that of fore leg; apical comb on posterior side of hind tibia absent; posterior hind tibial spur about 7x longer than maximum width at base, about 0.35 x length of long basitarsus; tarsal claws on all legs completely and distinctly pectinate in palliventre, pectination not apparent in tibiale. Fore wing areolet present; stigma short and very broad (Figs 1, 7), about 2 x longer that broad, Rs+2r arising near basal middle of stigma. Hind wing (Fig. 8) with first abscissa of CU1 strongly reclivous and much longer than 1cu-a. T1 (Figs 1, 5, 9, 10) long, slender, parallel-sided from base to about mid-length, then gradually expanding posteriorly; straight, not decurved in profile (Figs 5, 10); dorsal carinae either absent posteriorad spiracles as in palliventre or extending full length of T1 though low and weakly developed (as in tibiale); basal depression at dorsal tendon attachment broad, shallow, but distinct; dorsal-lateral carina either complete and well-developed between spiracle and apex of T1 as in tibiale or poorly developed as in palliventre; glymma deep and large in palliventre (Fig. 10, somewhat obscured by dark pigmentation), essentially absent in tibiale_. S1 extending to or nearly to spiracle, the latter situated distinctly posteriorad midpoint of T1 (Fig. 10). T2 thyridium absent; laterotergites of T2 and T3 separated by creases from median tergite. Ovipositor and sheath straight or nearly so, directed posteriorly; ovipositor slightly longer than in _Pion, narrow basally, gradually becoming even narrower towards apex, without dorsal, subapical notch, apex very weakly upturned in both females of tibiale that were examined. The subgenital plate is relative small, not protruding beyond the apex of the metasoma.

This description is based largely on specimens of P. tibiale and _P. palliventre in the Texas A&M University Collection and is expanded from the original description given by Townes (1970), who also included Petilium in a key to genera of Pionini.

9830_mximage
1. Petilium tibiale habitus...
9832_mximage
2. Pet...
9835_mximage
3. Petilium tibiale face...
10593_mximage
4.Petilium tibiale
9831_mximage
5. Petilium tibiale head and mesos...
9836_mximage
6. Petilium tibiale m...
9833_mximage
7. Petilium tibiale fore wing...
9834_mximage
8. Petilium tibiale hind wing...
9837_mximage
9. Petilium ...
10594_mximage
10. Petilium palliventre T1 lateral...
 
Distribution
Known only from Chile as of 2015
Distribution
No referenced distribution records have been added to the database for this OTU.
Map

There are no specimens currently determined for this OTU, or those specimens determined for this OTU are not yet mappable.

Acknowledgements
This page was assembled by Bob Wharton as part of a larger collaborative effort on the genera of Ctenopelmatinae. Page last updated April, 2015.

This work would not have been possible without the groundwork provided by Ian Gauld’s study of the Australian and Costa Rican faunas, and we are particularly grateful for his assistance in many aspects of this study. We also thank the following curators for extended loans of the material used for this study: David Wahl of the American Entomological Institute and Andy Bennett of the Canadian National Collection. We also thank David Wahl for useful feedback throughout our study and especially John Heraty for collecting fresh specimens from Chile. Matt Yoder provided considerable assistance with databasing issues, and our use of PURLs (http://purl.oclc.org) in this regard follows the example of their use in publications by Norm Johnson. Heather Cummins, Andrea Walker, Patricia Mullins, Caitlin Nessner, Amanda Ladigo, and Cheryl Hyde graciously assisted with image processing, formatting, and literature retrieval. This study was supported by the National Science Foundation’s PEET program under Grant No. DEB 0328922 and associated REU supplement #s DEB 0616851, 0723663, 0923134, and 1026618.

This material is based upon work at Texas A&M University supported by the National Science Foundation under Grant Number DEB 0328922 with REU supplements DEB 0723663 and 0923134. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.