Phobaeticus chani Bragg, 2008

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 : 138-141

Phobaeticus chani Bragg spec. nov.

( Figs. 116–117, 181–183, 257–262, 313, 338, 379)

HT: ♀ & eggs (removed from body): Sabah, Penampang district, Ulu Moyog, c. 650 m, Native , 25.II.1989 ( BMNH, ex coll. CLC) .

PT, ♀: Sabah, Buntui, Sunsuron, J. Kulip, 10.X.1989 ( FRSC) .

PT, ♂: Sabah, Sipitang, Coll. Yong Ah Lok, 15.IV.1983 ( CLC) .

Further material [3 ♂♂]:

1 ♂: Sabah, Kinabalu Park HQ, 1600 m; coll. Toru Kikuta 03.IV.1993 ( KNP, No. SP /EPH/00021) ; 1 ♂: Kinabalu Park H.Q., Sabah E. Malaysia, 1500 m (a.s.l.), 5.IV.1991, Coll. H. Sadanori ( KNP, No. SP /EPH/00015) ; 1 ♂: Kinabalu Park , Sabah E. Malaysia, 600 m (a.s.l.), 21.7.1994, leg. Ladson ( KNP, No. SP /EPH/00020). [Examined from photographs only]

Diagnosis: This is the longest known extant insect of the world ♀♀ being readily distinguished from all other members of Phobaeticus by the extremely slender body and strongly elongated body segments, the abdominal segments II–VI being up to 6.5x longer than wide (at best 4.5x longer than wide in all other known species). The striking eggs of Ph. chani Bragg spec. nov. differ from all other eggs known from the genus by having the dorsoventral keel of the capsule elevated into large leaf-like lobes, and comparatively smaller oval micropylar plate (Figs. 181–183).

Closely related to the Bornean Ph. redtenbacheri ( Dohrn, 1910) , Ph. mucrospinosus spec. nov. from Sumatra and Ph. serratipes ( Gray, 1835) from Peninsular Malaysia, Singapore and Sumatra. From the first ♀♀ differ by: the larger size; slightly shorter median segment which is about equal in length to the metanotum; conspicuously shorter not lanceolate subgenital plate; lack of distinct spines of the praeopercular organ and lack of a distinct median lobe on the posterodorsal carina of the meso and metatibiae. Ph. mucrospinosus spec. nov. differs in the presence of remarkable dagger-like spines on the ventral carinae of the mesofemora and the much smaller size. From Ph. serratipes ♀♀ differ by: the larger size and more slender body; lack of distinct triangular lobes of the praeopercular organ; enlarged sub-basal spine on the ventral carinae of the meso and metafemora and less numerous serrations of the profemora. Also related to Ph. kirbyi Brunner v. Wattenwyl, 1907 from Borneo, but the larger size, relatively longer body segments, longer subgenital plate and more elongate and flat head easily distinguished it from this species. Due to having well developed alae which reach about half way along abdominal segment V, broad semi-tergites of the anal-segment and an unarmed poculum (Fig. 261) ♂♂ strongly resemble those of Ph. ingens ( Redtenbacher, 1908) from SE-India and N-Myanmar. They are however readily distinguished by the larger size, more elongate body, dark postocular stripe of the cheeks and comparatively more slender semi-tergites of the anal-segment.

Etymology: This new species, the longest known extant insect of the world, is named in honour of C.L. Chan (Kota Kinabalu, Sabah), who kindly loaned the ♀ HT and ♂ PT from his extensive phasmid collection and agreed to deposit both specimens in The Natural History Museum, London (BMNH).

Description: Both ♀♀ are damaged. The HT has part of left fore tibia, the fifth tarsomere of the right fore leg, and both antennae missing; the abdomen has been damaged by insect pests: five holes have been eaten into the dorsal surface, including one small hole in the anal segment (Fig. 257), and there is a small hole in the left hand edge of the pronotum (Fig. 313). The ♀ PT has the left mid leg and right hind leg missing, tarsomeres 1–4 are missing from the right foreleg, and 5 th tarsomere from left fore leg; the antennae are bent and difficult to measure. The ♂ PT lacks the left fore leg and has a broken right antenna; the fore tarsus has been glued back in position.

♀♀ ( Fig. 116): A very long and very slender species (body length incl. subgenital plate 333.5–357.0 mm) with spinose mid and hind femora. The HT is dark green with some whitish blotches on the thorax abdomen and legs; the head is creamy-brown with a brown line running from the eye to the back of the head (Fig. 313). The PT is discoloured, yellowish-brown rather than green, but the head is similarly marked and pale markings can be seen on the legs and body. Head, thorax and abdominal segments 1–6 smooth, 7–11 sethose.

Head broader than body, narrowing at the posterior. Pronotum narrow, widening towards posterior, twice as long as wide. Mesonotum widening evenly from about 4.0 mm at anterior to 5.0 mm at posterior, rest of body of uniform almost width (5.0– 5.5 mm). Metanotum and median segment of equal length. Body without any lobes or spines. Abdominal segments I–VI of increasing length, VII equal to II, combined length of VIII– IX less than VII. Segments X–IX with slight longitudinal carina. Supraanal plate short, triangular (Fig. 257). Apex of sternum VII with a depression. Abdominal tergites VII–XI, sternum VII, and subgenital plate sethose. Subgenital plate straight with a fine longitudinal carina, apex rounded (Figs 258–259), 1.0 mm longer than abdomen in HT, 3.0 mm in PT. Cerci conical, apex slightly upturned. Gonapophyses protruding slightly beyond supraanal plate.

All tibiae and femora with five distinct carinae which bear stiff setae. In most cases the carinae are expanded, to some degree, as a serrated lamella, the exceptions are: dorso-posterior of the profemur and protibia, and the medio-ventral of the meso and metafemora. Meso and metafemora spinose. All tarsi with a dorsal lobe on segments 1–3. Profemur and fore tibia triangular in cross section, the two dorsal carinae so close they are almost fused. All carinae except the dorso-posterior carina are lamellate; ventro-posterior and dorso-anterior carinae are serrated: dorso-anterior of fore femur with about 12 particularly notable serrations which decrease in size distally. Base of profemur strongly compressed and curved.

The carinae of the mesofemur are armed with spines and large triangular spine-like lobes, particularly notable are a large triangular lobe (2.5–3.0 mm long) near the base of the ventro-anterior carina, and one or two near the middle of the dorso-posterior carina (Fig. 338): HT with two on right leg and one on left, paratype without lobes on dorso-posterior. Dorso-anterior carina with only a few relatively small spines. Mesotibia with medio-ventral carina with triangular serrations, all others strongly spinose; dorso-posterior with a low-lying serrated lobe at the mid point (HT with a second very small serrated lobe on left tibia).

Metafemur with two notable spine-like lobes: one near the base of the ventro-anterior carina and one on the apical third of the dorso-posterior. Medio-ventral carinae with few spines. All ventral carina with spines, dorsal carinae serrated. Metatibiae armed as mesotibiae but the dorso-posterior carina has only two small lowlying serrated lobes in the mid section.

♂♂ ( Fig. 117): The male is brown with small white blotches on the legs, particularly on the hind tibiae. Some areas of the body and legs suggest the specimen may originally have been greenish in places. The head has a very dark brown line running from the eye to the back of the head. Costal margins of elytra and hind wings white. Body without any lobes or spines, mesonotum sparingly granulose, rest of body smooth.

Head broader than body, narrowing at the posterior. Pronotum narrow, widening towards posterior, about 1.5 times longer than wide. Body of uniform width (slightly less than 2mm), except abdominal segment VIII which widens to 2.8mm at the posterior. Metanotum and median segment not examined (hidden by wings). Anal segment slightly laterally compressed, rectangular when viewed laterally (Fig. 261). Poculum hemispherical (apex hidden by lateral margins of tergite IX, possibly due upward movement caused by shrinkage of abdomen). Cerci blunt, slightly swollen cylinders.

Wings reaching just beyond mid point of abdominal segment V. Legs with most of the carinae serrated with triangular spines. All tibiae with a triangular spine-like lobe on dorso-posterior carina before the mid point; mid and hind femora with similar, but smaller, lobes in this position. Mid and hind tibiae with apical lobe on both posterior carinae. Mid and hind femora with more serrations ventrally than dorsally; medio-ventral carinae less serrate than ventro-anterior and ventro-posterior. Fore femur with dorso-anterior and ventroposterior carinae serrated; dorso-posterior with only one or two serrations; ventro-anterior and medio-ventral not serrated. Mid and hind tibiae with very few spines on dorso-anterior carinae. Fore tibia with ventro-anterior and medio-ventral carinae unarmed; dorso-posterior with only one small spine and one large triangular lobe.

Eggs (Figs. 181–183): When the HT was originally collected it laid one or more eggs. One of these was illustrated by Chan and the illustration was seen by Bragg in 1990. However attempts to locate the egg(s) or drawing have been unsuccessful. The following description is based on eggs removed from the body of the HT. Capsule and operculum smooth, mid brown with a pale brown line along the ventral extension.

The capsule is a complex shape: it appears to be a typical laterally compressed sphere but with very large, curved extensions on midline of the dorsal and ventral surfaces. Viewed from the opercular end these extensions curve in a clockwise direction, they also extend beyond the polar end of the capsule; the extension is not present on the micropylar plate. Micropylar plate oval, positioned at about the mid point of the egg, near the polar end of the main capsule. Operculum oval, conical, capitular stalk quite long, capitulum small (possibly larger when laid).

The unusual shape makes useful measurements difficult; there is no clear demarcation between the capsule and the extensions to the capsule.

Measurements [mm]: Overall size (including extensions): length 9.4, width 2.4, height 4.5. Main capsule: length c. 6mm, width 2.4, height c. 3.3, capitular stalk c. 0.7.

* Table shows measurements for both the left and right legs

Comments: This new species is the world’s longest known extant insect. The longest specimen, the ♀ HT in BMNH, has a body length of 357 mm, exceeding the previous record of Phobaeticus kirbyi Brunner v. Wattenwyl by 40 mm. The overall length with the fore legs stretched out straight is 567 mm, but this would have been greater by 7–10 mm if the specimen was complete; this exceeds the previous record of 555 mm for a specimen of Phobaeticus serratipes (Gray) recorded by Seow-Choen (1997: 33).

The egg of this species is not typical of the genus although it can be considered a modification of the standard Phobaeticus pattern. The main capsule, operculum, and capitulum appear to be more or less typical but the large extensions on the dorsal and ventral surfaces radically alter the appearance. There are several possible evolutionary advantages of this egg shape. Related species are known to drop or flick their eggs from height. The extensions to the capsule undoubtedly increase air resistance and hence slow the fall of the egg which would offer two advantages: impact with the ground is lessened, reducing risk of damage and a slow descent would increase the dispersal by the wind. Other possibilities are that air trapped in the curved extensions would help keep the egg afloat in the event of flooding, and that the extensions would increase the chances of the egg becoming trapped in crevices above the ground.

Three ♂♂ in the Kinabalu Park collection (KNP) appear to be this species, based on photographs taken in December 2006. However, a more detailed examination is needed to confirm their identity.

Distribution (Fig. 379): Northern Borneo, endemic. Sabah (Penampang District: Ulu Moyog, c. 650 m; Sibitang; Kinabalu National Park 600 m; Kinabalu National Park headquarters 1500–1600 m & Buntui: Sunsuron).

Number of specimens examined: 6