Extatosomatinae Clark-Sellick, 1997

Hennemann, Frank H. & Conle, Oskar V., 2008, Revision of Oriental Phasmatodea: The tribe Pharnaciini Günther, 1953, including the description of the world's longest insect, and a survey of the family Phasmatidae Gray, 1835 with keys to the subfamilies and tribes (Phasmatodea: " Anareolatae ": Phasmatidae), Zootaxa 1906, pp. 1-316 : 46-48

4.5 Extatosomatinae Clark-Sellick, 1997 stat. nov.

( Figs. 1, 17–19, 63, 433)

Extatosomatini Clark-Sellick, 1997: 103 . Otte & Brock, 2005: 33.

Description: Large (body length ♂♂ 80–115 mm, ♀♀ 100–165 mm), the body broad and very massive in ♀♀, moderately slender in ♂♂. ♀♀ with tegmina and vestigial alae, ♂♂ with fully developed alae roughly reaching apex of abdomen. Head prognathous with the vertex strongly conically raised and spinose. Ocelli lacking in ♀♀, but prominent in ♂♂. Antennae at best as long as the head, pro- and mesonotum combined in ♀♀, much longer than the head and entire thorax and strongly pubescent in ♂♂; with less than 35 segments. Pronotum narrower than the head and rectangular to slightly trapezoidal, soinose in ♀. Mesothorax about as long (♂♂) or shorter than the head and pronotum combined (♀♀); strongly widened towards the posterior in ♀♀ with the posterior portion roughly 3x wider than anterior margin. Mesonotum slightly trapezoidal and in ♀♀ with a posteromedian pair of spines or spinose lamellae. Mesosternum moderately convex and at best with few slen- der spines. Metasternum flat and smooth (♂♂) or set with a few scattered spines (♀♀). In ♀♀ tegmina scalelike, with the anterior margin angulate and rougly reaching to posterior margin of metanotum; alae vestigial, shorter than tegmina and completely or in great parts covered by tegmina. ♂♂ with tegmina reaching about half-way along median segment, and alae well developed, reaching to about apex of abdomen. Anal region transparent with slight brownish mottling. Median segment slightly shorter than the metanotum in ♀♀, considerably longer in ♂♂. Abdomen excluding median segment longer than head and complete thorax combined. Abdomen slender in ♂♂ with tergites II–VII> 1.5x longer than wide and unarmed; V–VII with large, roundly angulate lateral lobes. Abdomen of ♀♀ very massive with the basal tergites transverse and V–VII bearing very large and spinose, foliaceous lateral lobes. Tergites II–VII each with one or two pairs of spinose lamellae and tergites VIII–X considerabyl narrower than previous. Sternites II–VII strongly rugulose in ♂♂ and all over set with long, slender spines in ♀♀. Praeopercular organ lacking in ♀♀. Aanal segment of ♂♂ strongly tectiform, consisting of two semi-tergites which have the ventro-apical angles expanded into a short and in-curving finger-like process which bears 5–6 distinct terminal teeth ( Figs. 17–19). External vomer in ♂♂ lacking. Cerci rather small, laterally compressed, carinate and slightly lanceolate, about as long (♂♂) or considerably shorter (♀♀) than the anal segment. Poculum of ♂♂ very bulgy, deep and cup-like. Subgenital plate of ♀♀ boat-shaped, acutely longitudinally keeled and roughyl reaching apex of the abdomen; basal por- tion of the subganital plate with the median keel strongly raised and dentate. Gonapophyses of ♀♀ elongate, filamentous, up-curving apically and slightly extending over apex of subgenital plate. Legs all rather short, robust and furnished with large, dentate ± foliaceous appendages and spines. Profemora trapezoidal in crosssection with dorsal carinae strongly nearing and medioventral carina lacking; all carinae with ± distinct dentate lobes. The remainder femora and all tibiae triangular in cross-section with the anterior carinae melted and forming one or two large, dentate foliaceous lobes. Anteroventral carinae of mid and hind legs roundly elevated and dentate, the posteroventral carinae spinose, that of the metatibiae in particular armed with prominent hooked spines. The dorsal and anteroventral extensions of the mid and hind legs together form a large, almost plain lateral surface of the corresponding femur or tibia. Medioventral carina of meso- and metafemora very faint but set with a few small spines. Probasitarsus about as long as following three tarsomeres combined and with a ± apical dorsal lobe in ♀♀. Meso- and metabasitarsi slightly shorter.

Eggs ( Fig. 63): Moderately sized (overall length 4.5–6.5 mm), capsule ovoid with the polar-area slightly narrowed. Capsule surface very gently rugose or punctured and ± glabrous. Colouration variable, usually pale cream or grey and irregularly marbled with brown or dull green. Micropylar plate very elongate, parallelsided, extending from the opercular rim to the posterior pole of the capsule and set conspicuously above the capsule surface; pale colour strongly contrasting with the capsule. Various degrees of expansion are seen in the region of the micropylar cup. Internal micropylar plate closed with the micropylar stalk well within the borders of the plate ( Fig. 63b) and connected to the surface with an inwardly turning lip (Clark-Sellick, 1997: 103). Operculum convex and with a prominently raised, irregulary cone-shaped or funnel-like capitulum.

Comments: Both, Günther (1953: 553) and Bradley & Galil (1977: 195) omitted to mention Extatosoma in their taxonomic arrangement of the order and since the genus had been treated as a member of Tropidoderinae : Tropidoderini . Based on the striking features of the insects, such as the strongly conically elevated head, foliaceous appendages of the abdominal tergites and large leaf-like extensions of the femora and tibiae, as well as egg-structures Clark-Sellick (1997: 103) removed Extatosoma from Tropidoderini and established the tribe Extatosomatini to contain it. Due to the laterally compressed cerci, distinct clasping apparatus of the anal segment of ♂♂ and derived copulation position (Fig. 433) in which ♂♂ grasp the base of the ♀♀ subgenital plate, Brader (2001: 181) contained Extatosomatini in Lanceocercata. Indeed, the mentioned features show close relationship to taxa of this group, hence Extatosomatini must be regarded a member of Phasmatidae s. str..

Indeed, the following striking features at once distinguish the highly cryptic Extatosomatini from entire Tropidoderinae and well characterise it amongst the family Phasmatidae s. str.: head prognathous with vertex strongly conically raised and spinose; abdominal tergites of ♀♀ with paired spinose lamellae dorsally; tergites V–VII with greatly expanded, leaf-like lateral lobes (spinose in ♀♀); abdominal sternites II–VII of ♀♀ spinose; subgenital plate of ♀♀ with the longitudinal keel dentate basally; meso- and metafemora and all tibiae distinctly triangular in cross-section with dorsal carinae melted and forming very large, dentate lobes. Furthermore, ♀♀ exhibit the remarkable ability to curl over their abdomen with live insects usually found in a very characteristic position, and eggs have the very long micropylar plate conspicuously set above the capsule surface. Consequently, as these features, most of which may represent apomorphies, cleary distinguish Extatosomatini from Tropidoderinae and any other subfamily of Phasmatidae s. str., Extatosomatini is here raised to subfamily level. Since Extatosomatinae is monotypic the tribe Extatosomatini is technically not needed anymore.

The rather basal ground pattern of Extatosomatinae , like the remarkably prognathous head, presence of distinct ocelli in the ♂♂ and short thorax, suggest this group must have splitted off rather early from the remaing Phasmatidae . Mainly in behavioural aspects Extatosomatinae however shows to be highly specialized, which concerns to the ability of adult ♀♀ to curl their strongly procryptic abdomen forward over the ir back and symbiosis of the Australian E. tiaratum Mac Leay, 1826 with ants of the genus Leptomyrmex Mayr, 1821 ( Formicidae : Dolichoderinae ) in its natural habitats ( Key, 1991 and Hughes & Westoby, 1992). The ability to curl the abdomen is observed in nymphs of many Phasmatodea , but none retain this ability in such degree in the adult insects. The ♀♀ of several species (e.g. of the genus Eurycnema Audinet-Serville, 1838 ) slightly curl up their five terminal segments, but in Extatosomatini the complete abdomen is curled forward from the 2 nd segment onwards, with the apex of the abdomen almost touching the dorsal surface of the body near the wings or median segment. This peculiar behaviour is supported by extensive membranes between the abdominal segments and requires a strong and specialized dorsal and ventral musculature internally. In nymphs the curled up abdomen is perhaps a specialisation due to the symbiosis with ants that are known to be used as a host to hatch the eggs in their formicary. The ants are attracted by the nutritious capitulum as a food source with the rest of the egg discarded in their nest. This benefits the phasmids as it helps dispersal and a decreases the rate of parasitism. The aposematic colouration of black, with an orange head and white collar on the mesothorax, in the newly hatched nymphs remarkably mimics the Leptomyrmex ants in colour, posture and movements, and thus insures the nymphs to escape from the formicary safely ( Key, 1991: 402). This symbiosis has also been reported from other Australian species whose eggs bear a capitulum ( Hughes & Westoby, 1992) but in neither species the nymphs represent “ant mimics”.

A revision of the genus Extatosoma at the species level was provided by Brock (2001).

Distribution ( Fig. 1): East Coast of Australia and New Guinea.