The Wharton Lab

Coelorhachis Townes, 1966: 329. Type species: Mesoleptus decorosus Cresson, 1868. Monotypic and original designation.

Coelorachis: Townes (1970: 87), misspelling.

Coelorhachis: Gauld (1997: 220-227), revision.

In his redescription of Coelorhachis, Gauld (1997) stated that there was no distinct tyloid on the first flagellomere. This is true for several of the specimens I have examined, but this may be partly a preservation artifact since a tyloid is present on some of the other specimens. When visible, individual sensilla tend to be not as tightly clustered as in most other perilissines that possess a tyloid.

The position of fore wing 2m-cu as it enters the areolet is somewhat more variable than indicated by Gauld (1997). Some specimens I have examined from Mexico have 2m-cu entering at the midpoint of the posterior margin of the areolet or slightly distad.

Many of the species of Coelorhachis are yellow with black markings similar to those shown in the figures above.

At least some of the specimens I have seen from Chile, though conforming to the definitions of Coelorhachis proposed by both Townes and Gauld, are slightly different in clypeal configuration: possessing small, thin lateral teeth.

Five valid species are presently known:
Coelorhachis decorosa (Cresson, 1868), Nearctic
Coelorhachis edithae Gauld, 1997, Neotropics
Coelorhachis felipei Gauld, 1997, Neotropics
Coelorhachis gloriae Gauld, 1997, Neotropics
Coelorhachis heineri Gauld, 1997, Neotropics

Gauld (1997) made an important contribution to our understanding of the poorly known neotropical group to which Coelorhachis belongs by describing the closely similar Jorgeus and by providing the first clear diagnosis for Coelorhachis. Gauld (1997), who focused primarily on the Costa Rican fauna, restricted Coelorhachis to those species with a complete fore wing areolet, reduced propodeal carination, a complete occipital carina meeting hypostomal carina at or above base of mandible, a transverse male subgenital plate, and lacking three features variously used to characterize certain other perilissine genera: a notch in the back of the head, specialized teeth on the hind tarsal claws, and strong dorsal carina on T1.

Coelorhachis belongs to a group of genera in which the dorsal tendon attachment is set within a deep basal median pit, with the glymmae extending towards the pit rather than meeting posterior to the pit to form a median, translucent window as in Perilissus and many other genera. Gauld (1997) included the Neotropical Tetrambon and Sialocara in this group as well as the Holarctic Lathiponus, Synoecetes, and Zaplethocornia. Gauld also noted that there were several undescribed neotropical genera that belonged to the group, but it is not clear whether his statement referred to the three genera newly described and assigned to the “Coelorhachis group” in this work (Jorgeus, Peakelestes, and Xiomara), or whether he had other undescribed genera in mind. Examination of neotropical material now accumulating in several collections reveals a rich diversity within this group, suggesting the need to describe several new genera to accomodate this diversity. As Gauld (1997:222) noted, however, a great deal of work is needed to establish the monophyly of genera in this group and thus provide a more solid basis for generic assignment of species.

Clypeus with ventral margin varying from bluntly rounded and thick to more angulate; without small lateral tooth or projection; ventral margin convex; epistomal sulcus present, distinctly impressed in most species, clypeus in profile usually angled outwardly from face. Malar space distinct, very short (0.2 x basal width of mandible) to moderately long (0.3-0.5 x basal width of mandible). Mandible broad basally, ventral tooth longer to much longer than dorsal tooth. Lateral ocellus distinctly shorter than distance between ocellus and eye. Maxillary palp shorter than head height (Fig. 1); female antenna varying from shorter than to a little longer than body; first flagellomere usually with irregular tyloid containing 15 or fewer sensilla. Hypostomal carina often joining occipital carina well before base of mandible, sometimes meeting occipital carina at base of mandible; occipital carina complete. Dorsal end of epicnemial carina distant from anterior margin or mesopleuron, usually curving away from margin. Notaulus usually absent, rarely very weakly impressed at extreme base. Broad, v-shaped, indistinct groove present between propodeum and metanotum in lateral view, not resembling narrow, u-shaped groove typical of Absyrtus, Neurogenia, and Opheltes; pleural carina complete, well-developed; propodeal carinae (Fig. 4) absent anteriorly, posterior transverse carina present, with apical branches of longitudinal carina variously developed to form median petiolar area and adjacent lateral areas in posterior 0.6-0.7 of propodeal field, median areola absent. Apex of mid tibia evenly rounded, without small tooth similar to that on fore tibia; apex of hind tibia with indistinct comb, blending with remaining setae that densely cover posterior surface of hind tibia; posterior hind tibial spur at least 7x longer than maximum width at base; tarsal claws pectinate, the teeth sometimes widely spaced and not reaching apex. Fore wing (Figs 1, 2) with areolet present, large; stigma usually relatively narrow, Rs+2r arising slightly basad middle of stigma. Hind wing with first abscissa of CU1 distinctly longer than 1cu-a. T1 not long and slender, broadening posteriorly, without discrete dorsal carinae, though basal 0.5-0.6 elevated medially and depressed laterally in many species, giving appearance of a broadly rounded ridge; dorsal surface moderately arched; basal depression at dorsal tendon attachment deep (Fig. 3), extending internally towards T2; dorsal-lateral carina usually sharp from spiracle to apex of T1, sometimes weaker, more rounded, or nearly absent; glymma broad, deep, extending into median basal depression, the two glymmae not meeting on each side posterior to basal depression. T2 thyridium absent; laterotergites of T2 and T3 completely separated by creases. Ovipositor (Fig. 5) straight, short, with very broad, shallow, subapical depression, the apex of the upper valve somewhat swollen; ovipositor sheath narrowly rectangular, bluntly rounded to nearly trunctate apically. Male parameres short, broadly triangular, never strongly attenuate posteriorly, usually with one longer, stouter, ventrally directed seta along posterior margin; aedeagus rounded and weakly clubbed distally.

The described species of Coelorhachis are known from Texas and Costa Rica. The known range (based on described plus undescribed species) extends from Texas south to northern Argentina (Gauld 1997) and southern Chile (Townes 1970). In light of Gauld’s restricted definition of the genus, Chilean records will need verification.

Hosts unknown; Gauld (1997) provides some habitat and phenological data for species from Costa Rica.

This page was assembled by Bob Wharton as part of a larger collaborative effort on the genera of Ctenopelmatinae. 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 David Wahl for useful feedback throughout our study. 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. Andrea Walker, Amanda Ladigo, and Cheryl Hyde graciously assisted with image capture, 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 nos DEB 1026618. Page last updated June, 2011.

This material is based upon work supported by the National Science Foundation under Grant Number DEB 0328922 with REU supplement DEB 1026618.
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.