Phyllium (Walaphyllium) lelantos sp. nov.

Cumming, Royce T., Thurman, Jessa H., Youngdale, Sam & Tirant, Stephane Le, 2020, Walaphyllium subgen. nov., the dancing leaf insects from Australia and Papua New Guinea with description of a new species (Phasmatodea, Phylliidae), ZooKeys 939, pp. 1-28 : 1

Phyllium (Walaphyllium) lelantos sp. nov. Figs 3E , 13A, B , 14A-D

Type material.

Holotype ♂: Papua New Guinea, Watut, Morobe Province, I.1992. NHMUK 012497024. Deposited in the Natural History Museum, United Kingdom (NHMUK), (Fig. 3E ).

Discussion and differentiation.

The female and eggs are currently unknown; therefore, differentiation is only given for male morphology. This new species is the smallest within the newly erected subgenus, with the holotype only 53.3 mm long, versus males of P. monteithi 61.0-64.0 mm or P. zomproi at 79.0 mm (Figs 3B , 3D , versus 3E). An easy morphological feature to differentiate males of the three species is the radial venation of the tegmina. In P. lelantos sp. nov. the radial vein is split only once into the first radial and the radial sector; P. zomproi has the radial split twice, into the radial sector, the first radial, and the second radial; P. monteithi has the radial split more than the others with at least four prominent radials as well as the radial sector (and occasionally a weak but present fifth radial near the wing apex is also present in some specimens). The profemoral exterior lobe is also notably thinner in P. lelantos sp. nov. only one or one and a half times wider than the profemoral shaft width (Fig. 14B ) versus P. monteithi and P. zomproi which can have a profemoral exterior lobe width as many as two or two and a half times wider than the profemoral shaft (Figs 6B , 8B ).

Morphologically, P. lelantos sp. nov. appears to be most similar to P. monteithi based on the thorax spination, with the less pronounced mesopleurae tubercles and the anterior prescutum rim with a weakly formed sagittal tubercle (Fig. 14D ) versus the prominently raised anterior prescutum rim in P. zomproi (Fig. 7E ). Another similarity of P. monteithi and P. lelantos sp. nov. are the terminal abdominal segments with the lateral margins of abdominal segments VIII and IX having straight converging margins, versus P. zomproi which has rounded terminal abdominal segments.

Description.

Female and egg. Unknown.

Male. Coloration. Coloration description is based on the single preserved holotype specimen. It is expected that live individuals are likely vibrant green in life. Overall coloration green throughout with yellow to tan discoloration in places due to the drying of the specimen. Compound eyes and the four terminal antennae segments are of a rusty brown color darker than the tan on the head or thorax. The rest of the antennae are of a tan to green color. The protibial interior lobe has brown marking throughout most of the surface, this is the only lobe that has brown colorations, the others are a normal green like the rest of the body. The head through to the thorax are more tan than green in the dried specimen but were likely a darker green in life. There are two faint circular eye spots on the fifth abdominal segment with all others lacking markings.

Morphology. Head. Head capsule slightly longer than wide, with a vertex marked by sparse, small evenly sized nodes. Frontal convexity stout with sides that converge to the point which is slightly recurved, not straight; the surface is sparsely covered in thin transparent setae (Fig. 14A ). Antennae. Antennae consist of 22 segments (including the scapus and pedicellus). The scapus and pedicellus lack setae, the terminal five antennae segments are covered in dense setae that are short, and the remaining antennae segments are covered in long, thin setae which are longer than each segment is wide. Compound eyes are large, notably protruding away from the head capsule and taking up about half of the length of the capsule lateral margins (Fig. 14A ). Ocelli are present and well-developed (Fig. 14A ). Thorax. Pronotum with anterior margin that is slightly concave and lateral margins that are straight and uniformly converging to a straight posterior margin that is about half the width of the anterior rim. Anterior and lateral margins of the pronotum have distinct rims, and the posterior margin lacks a rim (Fig. 14A ). Face of the pronotum is marked by a distinct sagittal and transverse furrow meeting at a central pit with the remainder of the surface slightly lumpy in texture. Prosternum is moderately granulose throughout with nodes of even size and slightly uneven spacing as well as a slightly more prominent central node which is more prominent than the others (Fig. 14D ). Mesosternum surface wrinkled and marked with nodes throughout. Prescutum anterior margin is wider than the prescutum is long, with lateral margins that converge to the posterior margin that is approximately three-quarters as wide as the anterior rim. Lateral rims with five nodes of slightly varying size but nearly even spacing. Prescutum crest along the sagittal plane nearly bare, with only a single small node present near the anterior rim and one more small one near the posterior, the rest of the sagittal crest lacks features and is just smooth (Fig. 14D ). Prescutum anterior margin not particularly prominent, only marked with a single small tubercle (Fig. 14D ). Mesopleurae narrow, with margins which are straight, only slightly diverging along their length. Lateral margin marked with six tubercles spread throughout the length almost evenly, with the smallest near the anterior rim and the rest slightly increasing in size as they span towards the posterior (Fig. 14A ). Face of the mesopleurae smooth except for two faint divots, one on the anterior third and one on the posterior third. Wings. Tegmina short, only extending half way through abdominal segment III. Tegmina venation can only be noted to the best of our ability from the folded wings of the holotype specimen. For the tegmina, the subcosta (Sc) is the first vein and rather long, running smoothly along the wing and terminates just past the midline of the wing length. The radius (R) spans the entire length of the tegmina with the radial sector (Rs) terminating at the wing apex and a single first radius (R1) branching just before the midline and terminating at the margin three quarters of the way through the tegmina length. The media (M) also spans the entire length of the tegmina (as the media anterior MA, which terminates at the wing apex). There are two posterior media veins, the first posterior media (MP1) branches before the midline and meets the cubitus at the wing margin where the first posterior media terminates. The second posterior media (MP2) branches after the first posterior media near the midline and meets with the cubitus near the wing margin. The cubitus (Cu) vein runs along most of the tegmina margin and terminates about three quarters of the way through the tegmina length upon meeting the second media posterior. The first anal (1A) vein terminates upon reaching the cubitus about one-third of the way along the tegmina length. Alae long and well developed in an oval fan configuration, extending to the posterior margin of abdominal segment IX. Alae wing venation cannot be seen fully due to the folded wings, but what can be seen is that there is a fully developed costa (C), subcosta (Sc), and first radius (R1) present along the length of the alae running parallel with each other to the apex of the wing. Abdomen. Abdominal segments II through the anterior half of IV gradually and uniformly diverging, posterior half of IV through VII parallel, with each segment only about one and a half times wider than long giving the abdomen a thin boxy appearance. Segments VIII through X converging to the apex but with slightly rounded margins, not perfectly straight. Abdominal segment X has margins which are lined with stout setae, very similar to those which line the cerci margins. Genitalia. Poculum starting at the anterior margin of abdominal segment VIII, uniformly broad throughout its length, and ends in a broad slightly rounded apex that slightly passes the anterior margin of segment X (Fig. 14C ). Cerci about as long as the vomer, with about half of the length extending from under abdominal segment X. Cerci are slightly cupped and have a surface which is weakly granular. Cerci margins are lined with stout tan setae with those on the exterior margins more prominent than those on the interior margins. Vomer moderately long, extending about three-quarters of the way under segment X with sides that are evenly converging, the single apical point is broad and hooks upwards into the paraproct (Fig. 14C ). Legs. Profemora exterior lobe slightly wider than half the width of the interior lobe, no small teeth are present but the entire length has short tan setae relatively evenly spaced, and the lobe arcs smoothly along the profemoral shaft without a distinct bend. Profemoral interior lobe roundly triangular without a strong angle and marked with five teeth. The proximal most tooth is smaller than the rest but clearly present, the remaining four teeth are of a similar size and with wide looping spacing except between the distal two which have slightly wider spacing than the others. Exterior mesofemoral lobe arcs end to end with a slight rounded angle in the center, and only on the distal half of that gentle bend are three to five small serrate teeth. The exterior mesofemoral lobe ends in a prominent spur near the mesotibial joint, this spur is larger than any of the preceding small serrate teeth. Interior mesofemoral lobe is slightly narrower than the exterior lobe and lacks a distinct bend, instead hugging the mesotibial shaft. On the distal half only of the interior mesofemoral lobe there are five to six serrate teeth which are larger than the exterior lobes teeth. Metafemoral exterior lobe lacks teeth, is nearly straight, and runs uniformly along the metafemoral shaft. Metafemoral interior lobe slightly wider than the exterior lobe and with nine to ten small serrate teeth throughout slightly more than half of the length. Protibiae lacking an exterior lobe, interior lobe reaching end to end in a smooth scalene triangle, with the broadest portion on the distal end (Fig. 14B ). Uniformly throughout the protibial lobe margins are similar stout setae as those found on the profemoral lobes margins. Meso- and metatibiae simple, lacking lobes completely.

Etymology.

Noun. Because leaf insects are such cryptic insects so rarely observed, or in this case only known from a single specimen, we felt that the homage of Lelantos the Greek minor Titan of "moving unseen" was fitting. Lelantos’ name is derived from the Greek Ληλαντος ( lêthô, lanthanô, and lelathon), meaning "to escape notice", "move unseen", or "go unobserved" ( Rouse 1942).

Distribution.

Only known from the holotype specimen from Papua New Guinea, Morobe Province, Watut (Fig. 4 ).

Measurements of holotype [mm].

Length of body (including cerci and head, excluding antennae) 53.3, length/width of head 3.8/2.8, antennae (but slightly bent so measurement is slightly off) 12.0, pronotum 2.5, mesonotum 1.5, length of tegmina 15.1 (left) and 11.8 (right, which appears to be slightly aberrant and dwarfed), length of alae 38.5, greatest width of abdomen 10.5, profemora 7.4, mesofemora 8.8, metafemora 11.0, protibiae 5.8, mesotibiae 5.7, metatibiae 7.5.

Figures

Figure 3. Dorsal view of the known species within the Phyllium (Walaphyllium), scaled to relative size to show the size differences between species A Phyllium zomproi female, Coll SLT B Phyllium zomproi male, Coll RC 17 - 336 C Phyllium monteithi female dorsal, Coll RC 16 - 067 D Phyllium monteithi male dorsal, Coll SLT E Phyllium lelantos holotype male, NHMUK. Scale bars: 10 mm.

Figure 4. Distribution map for the known species of Phyllium (Walaphyllium) between Papua New Guinea and Australia.

Figure 6. Phyllium zomproi. A female, profemora and protibia, dorsal, Coll RC 18 - 277 B male, profemora and protibia, dorsal, Coll RC 17 - 336 C female, genitalia, ventral, Coll RC 18 - 277 D male, genitalia, ventral, Coll RC 17 - 336.

Figure 7. Phyllium zomproi. A female, head through thorax, dorsal, Coll RC 18 - 277 B male, head through thorax, dorsal, Coll RC 17 - 336 C female, antennae, dorsal, Coll SLT D female, lateral, head through thorax, Coll RC 18 - 277 E male, lateral, head through thorax, Coll RC 17 - 336.

Figure 8. Phyllium monteithi. A female, profemora and protibia, dorsal B male, profemora and protibia, dorsal C female, genitalia, ventral D male, genitalia, ventral E female, thorax, dorsal F male, thorax, dorsal. All specimens, Coll SLT.

Figure 13. Phyllium lelantos sp. nov. holotype male, NHMUK. A dorsal B ventral. Insert Data labels, " Papua New Guinea, Watut, Morobe Province, I. 1992; NHMUK 012497024 ".

Figure 14. Phyllium lelantos sp. nov. holotype male. A head and thorax, dorsal B front leg, protibiae and profemora, dorsal C genitalia, ventral D thorax, lateral view.