Elasmostethus Fieber

Genus Elasmostethus Fieber View in CoL

Elasmostethus Fieber, 1860: 78 , type species: Cimex dentatus De Geer, 1773: 260 (= Cimex interstinctus Linnaeus, 1758: 445 ), monotypic.

Dichobothrium Breddin, 1903: 207 , type species: Dichobothrium sastragaloides Breddin, 1903: 209 (synonymized by Kumar, 1974: 51).

Kumar (1974) proposed the following definition of Elasmostethus : jugum not extending beyond apex of tylus; antennal segment I extending beyond apex of tylus; rostrum reaching from hind coxae to posterior end of abdominal segment III; bucculae not united posteriorly; maxillary plate usually without a tubercle; humeral angle sometimes projected; prosternum with a median groove; mesosternal carina similar to that of Elasmucha , extending anteriorly to fore coxae, sometimes to prosternum or head, posteriorly to middle coxae, sometimes to hind coxae; scent gland spout elongate, ⅔ or more of metapleuron width, sometimes reaching lateral margin of metapleuron; abdominal spine usually reaching to middle coxae, rarely beyond them; Pendergrast’s organs absent, but sometimes abdominal sternum VI with paired spots.

Japanese members of the genus are characterized by the following body features: body ovoid with rounded sides, broadened anteriorly; dorsum green with red markings, densely dark punctuated; head triangular with laterally concave jugum; antennal segments III- V densely pubescent; anterior part of pronotum strongly declinate, angulated at anterior corners and with thickened lateral margins; humeral angle weakly projecting with obtuse apex; scutellum triangular, clearly longer than broad, with short apical tip; corium with weakly rounded costal margin and with slightly sinuate membranal margin; mesosternal carina anteriorly reaching middle of prosternal groove and posteriorly reaching hind coxae; scent gland spout ⅔ times as wide as metapleuron; legs densely pubescent on apical ⅔ of tibia and ventral part of tarsus; male hind femur with a small basal tubercle; connexiva concolorous, not serrate; abdominal spine reaching to middle coxae; apical corner of abdominal segment VII acute in both sexes. Pendergrast’s organs obviously present on abdominal sterna VI and VII in female.

The male genitalia of Japanese Elasmostethus in general show the following characteristics: The genital capsule is furnished with a pair of long setal tufts at the middle of ventral rim, here referred to as ‘lower tufts’ ( figs. 7-8, lt), and with a pair of dense tufts consisting of black, short and stout bristles ‘upper tufts’ ( figs. 7- 8, ut) at the upper region of the lower tufts. The proctiger is strongly projecting apically, and its basal part is convex laterally. The phallotheca is well sclerotized, strongly swollen at dorsobasal part, forming a large ‘dorsal diverticulum’ ( figs. 25-26, dd). The conjunctivum is weakly sclerotized, with a pair of strongly sclerotized lobes ventrally, which were termed ventrolateral conjunctival processes ( figs. 25-26, vcp) by Kumar (1974). The conjunctivum is also attached to a sclerotized, subconical extension apically, which was termed as sheath of conjunctiva by Leston (1953) and conjunctival sheath by Kumar (1974) ( figs. 25-26, cs). The conjunctival extension is usually accompanied by a large membranous sac dorsally, here referred to ‘dorsal lobe’ ( figs. 25-26, dl). However, in some Japanese species, the tufts of genital capsule and/or the dorsal diverticulum are lacking.

Remarks. – Kumar (1974) comprehensively revised the world Acanthosomatidae , redefining the 47 acanthosomatid genera, including Elasmostethus , and provided a generic definition and keys. He used two character states, the backwards-extending mesosternal carina and the elongated scent gland spout, to distinguish Elasmostethus from related genera (e.g., Acanthosoma Curtis, 1824 and Elasmucha Stål, 1864 ) in the generic key.

The genus Cyphostethus Fieber was synonymized with Elasmostethus by Kumar (1974), but Ahmad and Önder (1993) restored Cyphostethus as a separate genus. I examined the Japanese species Cyphostethus japonicus Hasegawa, 1959 ; it is clearly distinct from the members of Elasmostethus in the general body features, including the male genitalia. Therefore I am following Ahmad’s view in this work.

KEY TO THE JAPANESE SPECIES

1. Corium with a small fuscous spot on central region; abdominal sterna without dark spots except for female VII; male genital capsule without lower tufts at middle of ventral rim ( figs. 40-43).........2 – Corium usually lacking fuscous spot on central region; abdominal sternum with a pair of fuscous spots laterally (occasionally missing in some specimens); male genital capsule with a pair of lower tufts at middle of ventral rim ( figs. 7-18)...........3

2. Male genital capsule densely furnished with long setae on ventral rim ( figs. 40-41); paramere with an obtuse outer angle on apical part ( fig. 44); apical corner of abdominal segment VII extending beyond genital segments ( fig. 46)......... E. nubilus – Male genital capsule with only a few long setae on ventral rim ( figs. 42-43); paramere without outer angle on apical part ( fig. 45); apical corner of abdominal segment VII not extending beyond genital segments ( fig. 47) ......................... E. rotundus

3. Abdominal terga V- VII reddish yellow below wings................................................ E. humeralis – Abdominal terga almost entirely black below wings................................................................4

4. Males................................................................5 – Females.............................................................9

5. Ventral rim of genital capsule without upper tufts ( figs. 15-16) ....................................... E. amabilis – Ventral rim of genital capsule with a pair of upper tufts ( figs. 7-14, 17-18).....................................6

6. Ventral and lateral rims of genital capsule without black teeth..................................................7 – Ventral or lateral rim of genital capsule with black teeth........................................................8

7. Genital capsule with a pair of elongate and sinuate upper tufts on ventral rim ( figs. 13-14) ......... ........................................................ E. hasegawai – Genital capsule with a pair of oval upper tufts on ventral rim ( figs. 9-10)...................... E. kerzhneri

8. Lateral rim of genital capsule with black teethlike projections ( figs. 11-12)................... E. brevis – Ventral rim of genital capsule with a pair of small black lateral teeth ( figs. 7-8).......... E. interstinctus

9. Posterior corner of genital segment IX protruding beyond VIII ( fig. 36); lateral margins of abdominal terga broadly yellow ..................... E. amabilis – Posterior corner of genital segment IX not protruding beyond VIII; lateral margins of abdominal terga narrowly yellow......................................10 10. Posterior margin of genital segments VIII arched, scarcely emarginate medially ( fig. 34)..... E. brevis – Posterior margin of genital segments VIII distinctly emarginate medially ( figs. 32-33, 35)..........11

11. Antennae usually entirely infuscate; membrane infuscate; corium often with a fuscous long stripe along vein R+M ( fig. 6); genital segment VIII strongly rounded laterally ( fig. 35) .... E. hasegawai – Antennae fuscous only on apical segments; membrane not infuscate; corium without long fuscous stripe; genital segment VIII gently rounded laterally ( fig. 32-33)..................................................12

12. Membrane brownish......................... E. kerzhneri – Membrane not brownish .............. E. interstinctus