PLEURAL MORPHOLOGY IN SCELIONID WASPS (HYMENOPTERA: SCELIONIDAE) — AN AID TO HIGHER CLASSIFICATION

Abstract The importance of pleural characters in Scelionidae is discussed and assessed. Two new terms, peculiar to some Scelionidae, are proposed, viz. the netrion for a specialized area on sides of pronotum, and mesopleural carina for a diagonal keel on mesopleuron (mesepisternum). Netrion and mesopleural carina are considered important characters for higher classification of the Scelionidae. The proposed characters are reviewed in the suprageneric categories (tribes and subfamilies) of the Scelionidae. The tribe Tiphodytini n. stat. is reinstated and removed from the synonymy with Thoronini, partly on account of the pleural characters.


Introduction
The pleural region in Hymenoptera traditionally has received great attention from taxonomists. Numerous special terms were proposed to describe the variety of unique morphological structures. Perhaps the most elaborate pleural terminology has been applied in the superfamily ~~h e c o i d e a (digger wasps) the summary of which was presented recently by Bohart and Menke (1976). Pleural characters were also used for higher classification of various groups of Hymenoptera and became an integral partof generic keys, descriptions, differential diagnoses, etc.
In the family Scelionidae (superfamily Proctotrupoidea), however, the pleural region has been almost completely ignored and remained unexploited for higher classification. Similarly, the terms for pleural morphology successfully used in other groups of Hymenoptera were not utilized in the Scelionidae. Except for a few studies where pleural characters were partly used at species level, this aspect has been neglected virtually since the classical works of Ashmead (1893) and Kieffer (1926). Thoracic characters used by classical authors or subsequent students for either higher classification or at species level were almost exclusively derived from the dorsal part of scelionid mesosoma. Conservatism and epigonism on the part of many students including the present author, is to be blamed for this neglected state of knowledge.
The purpose of this paper is to demonstrate the importance of pleural characters for higher classification of the family Scelionidae. It may be stated that some terms proposed in pleural morphology of other groups of Hymenoptera can be used also in the classification of scelionid wasps (e.g. acetabular carina, omaulus, sternaulus, etc.). However, the rich sculptural variety of scelionid pleuron requires more than what has been so far termed. his study aims to focus mainly on new terminology.
The following two new terms are necessary. Netrion (diminutive of netron, in Greek, a spindle; hereby meaning a spindlet, a small spindle). This is a specialized area (Fig. A, nt)on the flexed-sides of pronotum, between the prothoracic spiracle and fore coxa, situated anteriorly of the suture dividing pronotum from mesopleuron (Fig. A, su). Being a part of the pronotum the netrion is not, strictly speaking, a pleural character although it is located on the lateral part of the mesosoma. Wherever present the netrion is always distinctly higher than wide, in its most distinct shape truly spindle-like, with both upper and lower apices pointed. The latter form is termed netrion closed (Figs. 8-1 1) as compared with netrion open  in which case the anterior margin (Fig. A, a m ) of the netrion does not meet the promesothoracic suture above the fore coxa. The anterior margin of the netrion is most distinct when formed by a sharp keel running from the prothoracic spiracle down to the fore coxa. The latter form is termed netrion carinate (Figs. 1,(4)(5)(6)(7)(8)(9)(10)(11)(12)23) compared with netrion ecarinate (Figs. 2,14,(19)(20)(21)(24)(25)(26)29,30,32) when the anterior keel is absent and replaced by a row of crenulae or foveolae. The keel of the carinate netrion may sometimes be flanked inwardly by a row of foveolae enhancing the impression of a "suture" (e.g. Figs. 8,11,12). The dissection of this part of the pronoturn reveals however, no weakening of the sclerite; on the contrary a corresponding internal apodeme here probably serves as a muscle attachment. The netrion is usually distinguished from the adjacent parts of the pronotum by its markedly different sculpture (Figs. 4-7), or by being smooth compared with rougher sculpture of the pronotum (Figs. 29,30,32). However, the netrion may be indistinct in some groups, poorly distinguished or obscured by rough sculpture (Figs. 3,19,22,27,28), or not developed at all (Figs. 13,15,16). The principal shapes of the netrion appear to be constant not only at generic but often also at suprageneric levels. Therefore, the netrion is interpreted as an important character suitable for higher classification of the Scelionidae. This opinion has been already presented by Masner (1976), who, by mistake, wrongly interpreted the netrion as the prepectus. The present study is partially aimed to correct the latter error. Mesopleural carina (Fig. A , mc) is a term proposed for a keel ascending diagonally from the middle coxa (Fig. A, cx 2) up towards the suture dividing the pronoturn from the mesopleuron (Fig. A, su). Mesopleural carina only rarely attains the suture although its general course is usually directed towards the midpoint of the suture; however, its extreme upper tip is more or less upcurved (Figs. 8,(10)(11)(12)16,18,25,26). When developed, the carina marks the anterior margin of the mesopleural depression (Fig. A, m d ) , a large diagonal declivity on the mesepisternum designed for reception of the middle femur. The mesopleural depression and mesopleural carina are well developed in several groups of Scelionidae. However, in other groups of Scelionidae the depression is poorly defined and so is the carina.
Rarely, the mesepisternum is flat (Fig. 16) or even convex (Fig. 20); consequently, the depression is not developed at all in those cases. In some groups both depression and carina may be partly obscured by rough sculpture (Figs. 3, 17, 24, 27, 28).
The posterior margin of the depression is usually marked by a row of foveolae (Figs. 2,5,7,9,14,20,21,26,30) indicating simultaneously the division between the much larger mesepisternum (Fig. A , m s ) and the usually very narrow mesepimeron (Fig. A, m m ) . Compared with the netrion, the mesopleural carina (and particularly the adjacent sculpture) seems to offer more characters on the specific level and less useful characters for classification of higher categories.
The following brief review of the family Scelionidae is intended to illustrate the principal modifications of the netrion and the mesopleural carina.

tribes Figs. 1-22
Both the netrion and mesopleural carina reflect the magnitude and diversity of this subfamily by displaying various degrees of development. The 17 tribes involved, however, may be distinguished to a considerable extent by peculiar developments of the two structures discussed.