Homeomastax surda (Burr 1899)

Eumastax surda Burr (Plate VI, figs. 59-62.)
1899. Eumastax surda Burr, Anales Soc. Espafi. Hist. Nat., xxviii, pp. 258, 264.
[ 9 ; Chiriqui, Panama.] 46 1901. Eumastax surda Bruner, Biol. Cent.-Amer., Orth., 11, p. 23, pi. ii, figs. 14,
14a. [ 9 ; Chiriqui [Panama]; Bugaba [Chiriqui, Panama]; Peru (in error).]
The present species, the two here following it (veraguae and dentata) and carrikeri Hebard, from the Colombian Choc6, 47 constitute a well marked group of very closely related forms, inhabiting different areas, each apparently of limited extent. As far as known surda has the widest range of the four, being found at relatively low elevations in the Chiriqui district of western Panama and over parts of southwest and western Costa Rica. In the latter country it probably extends little, if at all, north of the Gulf of Nicoya region.
The species of the Surda Group are rather small and agree in their general similarity of size and proportions, but differ in less obvious features of the external genitalia of the males. The features separating these species have already been stressed in the key (see page 58) and need not be repeated in their entirety.
The present species and veraguae axe more nearly related to one another than they are to E. dentata, which differs mainly in the less decided production of the cau do-lateral angle of the tenth abdominal tergite of the male, and in the briefly fissate apex of the ultimate sternite (subgenital plate) of the same. Our knowledge of the female sex of the four species of the Surda Group is by no means full enough to warrant comparative discussion of their
46 This is given as "Chiriqui, Perou," an evident transcriptional or typographical error for the well-known district of Chiriqui, Panama.
47 Trans. Amer. Entom. Soc, xlix, p. 181, pi. xi. figs. 6, 7 and 8, (1923). [a 9 ; Andagoya, Antioquia (Choco), Colombia.) differential features, which latter are at best but slight. The determination of females of the genus Eumastax without accompanying males is exceedingly difficult, unsatisfactory and hazardous, and will remain so until sufficiently long series of perfectly preserved specimens are available to weigh properly the constancy of almost infinitesimal differences, which are found in the few available females accompanied by males collected at the same time.
The species surda was based on a single female, originally in the Brunner Collection and now the property of the Vienna Museum. The original description is not sufficiently exact to fix the name beyond possibility of question on any particular species, naturally lacking the distinctive features found in the male sex. In consequence the placing of surda is largely a geographic proposition. We are therefore using the name for the species which more nearly tallies with the description, and which we have from a region near to and environmentally more like the lower levels of Chiriqui Province, Panama, than is true of the other members of the group known to us. This seems the only logical course to follow with a species of which the unique female type specimen can give little or no definite assistance in the recognition of the species. So the species may be recognized with little difficulty, the following description of its more salient features should be of assistance.
cf ; Pozo Azul de Pirris, near junction of the Rio Grande de Pirns and the Rio Parrita, 48 western Costa Rica. Elevation 325 to 55ofeet. August 21, 1927. (C. H. Lankester and J. A. G. Rehn.) [Acad. Nat. Sci. of Phila.]
Size rather small (for genus) ; form as typical in genus, fully alate.
Head structure and proportions as in E. kressi except that the fastigio-facial interspace between the eyes is slightly broader, the lateral margins of the frontal costa ventrad of the median ocellus are less distinctly carinate, and the accessory facial carinae are less emphasized.
48 This locality is on the extreme northern border of the plain of the Pirns, immediately on the Rio Parrita but a very short distance above its junction with the Rio Grande de Pirris. It is an abandoned small cattle ranch building in fairly heavy forest country, with cane areas along the Rio Parrita. Immediately to the north the hill slope rises to the low, forest-covered mountain ridge which intervenes between the Rio Parrita and the Rio Colorado, a parallel tributary of the Pirrfs. The elevations collected on the south slope of the hills are covered by the extremes given above.
Pronotum slightly narrower on the dorsum than in E. kressi, cephalic transverse sulcus on the dorsum less definitely marked.
Tegmina and wings of same proportions as in E. kressi, but marginal field of tegmina proportionately narrow, with mediastine vein occupying middle of field for a greater portion of its length.
Tenth abdominal tergite with ventro-caudal angles (ventrad of cereal bases) acute, distinctly sharper than a rectangle; ultimate tergite (supra-anal plate) elongate lanceolate, distinctly acute produced, apex non-uncinate in profile; surface of tergite cut off from that of tenth tergite by a transverse arcuate impression, 49 which is usually quite evident in profile: cerci styliform, tapering, elongate, reaching as far distad as apex of ultimate tergite (supra-anal plate), apex blunt acute, more attenuate than in E. kressi, in lateral aspect nearly straight, in dorsal aspect slightly inbowed at apex: ultimate sternite (subgenital plate) less produced than in E. kressi, apex not distinctly rostrate, weakly produced, in profile blunt acute, seen from dorsum with dorsal margins weakly convex, acute convergent distad, in lateral aspect dorsal margins are shallowly convex in proximal two-thirds, thence to apex straight; disto-ventral surface of ultimate sternite briefly and finely carinulate.
Cephalic and median limbs slightly more slender than in E. kressi. Caudal femora with apices surpassing apex of abdomen by faintly more than twice the pronotal length.
A female, bearing the same data as the male described above, except that it was taken August 19, 1927, shows the following noteworthy differences from the female of E. kressi.
Size somewhat smaller
Head with the fastigio-facial interspace between the eyes proportionately broader, as in the male; frontal and accessory facial carinae as in the male.
Pronotum with dorsum slightly narrower, as in the male sex.
Tegmina with marginal field narrower proportionately and the mediastine vein in relatively the same position as in the male sex.
Ultimate tergite acute lanceolate, narrower than in the female of E. kressi, the apex more sharply acute, the dorsal surface briefly distad of middle subcompressed laterad, medio-longitudinal carina of distal half similar to but less definite than that of E. kressi, the proximal forking sharper and broader than in the latter: ovipositor jaws in ventral aspect faintly stockier and less elongate than in E. kressi,
49 The degree of emphasis of this varies according to the compression or other stress to which the apex of the abdomen of the dried specimen had been subjected. It is sometimes little evident, again strongly marked, and the two conditions taken by themselves might be considered to represent quite different species. Similarly compression of the tenth and ultimate sternites produces a marked longitudinal sulcation of rectangulate cross-section, giving an entirely different appearance to the whole area from that seen in less distorted specimens. Due to the relative softness of the integument the characters of this area must be carefully appraised and not over-emphasized. surface dentations less robust and strongly elevated : ultimate sternite (subgenital plate) with distal margin acute-angulate, immediate apex sharply acute produced, spicate, micro-crenulations of distal half of angulate margins evident.
Coloration. — Almost identical with that of E. kressi with a few noteworthy exceptions. The discoidal and anal veins of the tegmina are not distinctly pencilled with whitish; caudal tibiae almost completely lacking the pale preproximal annulus found in E. kressi.
Measurements (in millimeters)
Length of Length of Length of Length of
body pronotum tegmen caudal femur
d Pozo Azul, described
specimen 12.9 2.1 9.2 10. 1
cf , Same locality, average of
six 12.4 2.18 9 10
(11. 7-13) (2.1-2.26) (8.9-9.9) (99-10.5)
d Surubres 11. 9 2 8.1 —
9 , Chiriqui, type (ex Burr) 18 3 50 10 13 9 , Pozo Azul, described
specimen 16 2.35 10.9 13.7
9, Pozo Azul, average of
eleven 17.8 2.39 11. 2 13.2
(15. 5-18. 9) (2.27-2.43) (10. 5-12. 1) (12. 5-13. 8)
9 , Surubres, average of two 17.6 2.39 10.2 12.5
(2.35-2.43) (10-10. 3) (12-13)
Distribution. — Apparently the species surda occupies at least the lower levels of the Department of Chiriqui, Panama, probably only on the Pacific side to the southward of the Volcan de Chiriqui. Its distribution is probably continuous northwestward over the lower country of the Pacific side of Costa Rica wherever suitable conditions are present. It very probably is absent from the savanna type country of the lower Rio Diquis and the same is true of the semi-arid, typically Guanacaste condition found at the head of the Gulf of Nicoya and along the Rio Tempisque. The highest elevation from which we have seen it is two hundred and fifty meters on the Rio Surubres, which is a tributary of the Rio Jesiis Maria, western Costa Rica. At higher levels, at least in that region, it seems to be replaced by E. dentata. Nothing is
50 It is evident that this was taken hastily, and that it is too large for a member of this genus of the body bulk shown by the other measurements.
known regarding the eastern limit of its distribution toward that of E. veraguae. The senior author did not see it at Oricuajo on the lower Rio Jesus Maria, in park-like Guanacaste environment, although many species which had been secured at Surubres were there taken.
Biological Notes. — The species surda has habits similar to the other Central American species of the genus, occurring, however, in a relatively drier forest than that inhabited by E. kressi or sylvicola. That frequented at Pozo Azul was also more open with more light penetration than the sombre depths preferred by kressi. The actions of individuals were quite similar to those described for the latter species. The Pozo Azul immatures represent the two instars preceding maturity.
Specimens examined: 26; 7 d 13 9 ; 3 immature d 3 immature 9.
Costa Rica: Pozo Azul de Pirris; (M. A. Carriker, Jr.); 2 9 ; [Hebard Cln.]: May 10 to 20; (M. A. Carriker, Jr.) ; 1 9 ; [Hebard Cln.]; 325 to 550 feet elevation; August 19 to 24, 1927 (C. H. Lankester and J. A. G. Rehn; on foliage of undergrowth in forest and along clearing edge of same); 6 0*, 8 9,2 immature d 3 immature 9 ; [A. N. S. P.]. Surubres, near San Mateo, Rio Surubres, Pacific side, 250 meters elevation; January, 1906 and March, 1907; (P. Biolley); I cf, I 9, 1 immature d 1 ; [A. N. S. P.]. Bonnefil Farm, Rio Surubres, 700 feet elevation; October 17, 1909, (P. P. Calvert); 1 9 ; [A. N. S. P.].