Limnogonus lundbladi, Usinger, 1946

Usinger, Robert L., 1946, Hemiptera Heteroptera of Guam, Insects of Guam II, Honolulu, Hawaii: Bernice P. Bishop Museum, Bulletin 189, pp. 11-103 : 95-97

90. Limnogonus lundbladi , new species ( fig. 26 ).

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Relatively short and stout, dorsally humped at middle in apterous forms, with tremendously enlarged male genital segments and strongly, acutely produced last abdominal segment ventrally in female.

Apterous male: head two thirds as long as broad across eyes, the eyes large, two thirds as wide as interocular space, distinctly roundly emarginate on inner margins posteriorly. Rostrum reaching well onto mesosternum, the third segment reaching about to level of hind margins of front trochanters. Antennae almost as long as body, 99: 108; proportion of segments one to four as 31:21:20:27.

Pronotum relatively short and strongly convex, widest anteriorly and rounded anterolaterally, narrowed at about middle and thence gradually rounding to rounded apex; the ratio of subbasal width to width at middle to length as 25: 22: 42. Disk slightly depressed either side of middle anteriorly and feebly at about the middle. Metanotum and abdominal tergites strongly declivent, bounded laterally by strongly reflexed connexiva, the connexiva joining sinuate metathoracic carinae basally, strongly dilated at base of abdomen and arcuately converging posteriorly, about twice as wide at level of second visible abdominal segment as at apex of seventh. Basal abdominal tergites short, one fourth or less the length of seventh tergite at middle.

Under surface strongly convex, depressed between meso and metasterna. Metasternum almost as long at middle as the first five visible abdominal ventrites together, 7: 9, sixth visible ventrite (actually the seventh abdominal segment as counted dorsally) about half as long as the previous abdominal segments together, 5:9, deeply concave posteriorly.

Eighth and ninth abdominal segments (genital segments) together almost as long ventrally as meso and metasterna together, 30: 33, the eighth segment triangularly produced beneath ninth at middle, the apex subrounded, the length on median line slightly over half the length of ninth segment, 11: 19. Ninth segment strongly convex, three fourths as broad at base as long on median line, 15: 19, abruptly compressed on either side before middle to half the basal width and then subparallel to rounded apex. Eighth tergite about half as long as seventh but wider and distinctly roundly emarginate at middle of hind margin. Ninth tergite about as long as seventh but much narrower, broadest and feebly convex at base, tapering and rounded apically.

Legs relatively short and stout, front femora about as long as pronotum and about one fifth as thick at middle as long, arcuate along dorsal side and concave on basal half beneath; front tibiae scarcely shorter, 43: 40, slightly curved; tarsi about one third as long as tibiae, the basal segment approximately half as long as apical segment, 9: 19. Middle legs with femur, tibia, and first and second tarsal segments as 87: 78: 34: 8. Hind legs, 94: 56: 11: 7.

Body ·surface not conspicuously shining except anteriorly on pronotum, eyes, and posterior abdominal tergites. Pubescence inconspicuous and typical of the genus but with silver hairs confined to dorso-lateral areas of acetabula and the genital segments with a dense, erect, brown pubescence, especially ventrally.

Color dark brown to black above with head ochraceous at base and longitudinally sublaterally. Pronotum entirely surrounded with ochraceous, most broadly anterolaterally with a longitudinal ochraceous stripe at middle and a pale spot on either side of middle anteriorly. Abdominal tergites with a pale longitudinal line at middle, starting just behind metatergum and ending at middle of seventh abdominal segment. Middle connexival segments tinged with ochraceous sublaterally. Ventral and lateral surfaces largely pale with brown as follows: on prothorax behind eyes; mesothorax along upper margins of pleurites; at middle of pleurites anteriorly; at base of pleural suture; laterally at apex of acetabulum, and surrounding spiracular opening; metathorax surrounding pleurites and laterally on apical half of acetabulum; abdomen sublaterally beneath hind acetabula and coxae; and eighth sternite at apex and ninth laterally and apically. Antennae and middle and hind legs rather uniformly infuscated, rostrum pale with brown middle of front portion of third segment and black apex. Front femora pale with broad brown areas, tibiae brownish with more or less pale bases and apices, tarsi pale brownish.

Size: length, 5.25 mm., width (middle acetabula) 2.1 mm.

Apterous female: very similar to male but with front legs straighter and more slender, the femora distinctly shorter than pronotum, 37:42; proportion of segments 37: 37: 4: 9. Venter evenly convex, not depressed at base of metasternum, metasternum about twice as long as the first five visible abdominal segments together, the fifth (actually the sixth) with posterior margin feebly, broadly, roundly produced, the seventh segment long, strongly, acutely produced at middle apically, the length on median line almost as great as the remaining abdominal segments together, 23: 24, the ventral spine thus formed greatly exceeding female genital segments which are relatively short and rounded and visible only from above.

Size: length, 5.67 mm., width (middle acetabula) 2 mm.

Macropterous male: similar to apterous male but with pronotum widest across humeri, the proportion of width to length, 33: 51, the disk more convex thanin related species. Hemelytra complete, exceeding tip of abdomen, the veins black and membranous areas grayish. Mesothorax with a yellow lateral line oneither side suggestiveof f ossa.rUttH, but not tapering so conspicuously.

Size: length 6.8 mm., width (middle acetabula) 2.3 mm.

Holotype male, allotype female, male paramorphotype, and nine apterous paratypes, Mt. Chachao, May 16, Usinger ; one apterous paratype, headwaters of Talofofo River, June 17, Usinger .

This species was found only on the inland streams in the mountains of Guam. It is entirely distinct from any Limnogonus known to me though it might be considered as a member of the fossarum group, judging by the lateral thoracic stripes of the macropterous form. The short, stout body form approaches that of boninensis Matsumura (see figure in Iconographia Insectorum Japanicorum, 1646, 1932) but is shorter and more humped. The genitalia are entirely distinct.

This species is dedicated to Dr. 0. Lundblad. of the Naturhistoriska Riksmuseum in Stockholm who has given us a sound basis for the taxonomy of Limnogonus .

Figures

FIGURE 26.-Limnogonus lundbladi, ventral view (diagrammatic) of genital segments: a, male; b, female.