A new termite species of the genus Bulbitermes (Blattodea: Isoptera: Termitidae) from Meghalaya, India

RGNF-2017-18-SC-ASS-35335) scheme to K.S. Das. We are also grateful to Rodeson Thangkhiew, Graham Rani, and J. Nongdhar for their assistance during sample collection.


INTRODUCTION
Termites are widely spread group of insects that fall under the infra-order Isoptera and order Blattodea (Inward et al. 2007;Krishna et al. 2013a). Worldwide, around 2,933 living species of termites have been reported under 282 genera that belong to nine families (Krishna et al. 2013a). Family wise Termitidae is the largest among all the families and comprises of 2,077 species globally that belong to seven subfamilies. Among the subfamilies, Nasutitermitinae is the second largest with around 77 genera and 596 species reported from all over the seven biogeographic regions of the world (Krishna et al. 2013a). Nasutitermitinae group inhabits a variety of ecological conditions with diverse nesting and feeding habits (Eggleton 2000).
The genus Bulbitermes is the third largest genus (in species diversity) under the subfamily Nasutitermitinae and is endemic to the Oriental region (Chhotani 1997;Krishna et al. 2013a). It is a dead wood or plant material feeding nasutiform genus (Chuah 2005;Syaukani & Thompson 2011). This genus is similar to genus Hospitalitermes with constricted head behind antenna, mandibles with spine like processes and with more than 12 antennal segments in soldier castes. But the genus Bulbitermes differ from Hospitalitermes with comparatively less constricted head behind the antenna, mandibles with slightly shorter spine like processes and with hind legs not extending beyond the abdomen in soldiers (Chhotani 1997). The genus Bulbitermes comprises of 33 species. The Indian region (India, Bangladesh, Pakistan, Sri Lanka, Bhutan, Nepal, and Burma) houses four Bulbitermes species, viz., B. pyriformis Akhtar, 1975(From Bangladesh), B. prabhae, Krishna, 1965(From Burma), B. bulbiceps Maiti & Saha, 2000, and B. parapusillus Ahmad, 1965(from Meghalaya, India) (Krishna et al. 2013b. In this paper, we describe a new Bulbitermes species, Bulbitermes debadiliporum sp. nov., based on its monomorphic soldier and dimorphic worker (worker major and minor) castes from Meghalaya, India.

MATERIALS AND METHODS
The samples used in this study were collected from the betel nut plantation of Mawlynnong area, Pynursla, East Khasi Hills district and Nongkhrah village, Nongpoh, Ri-Bhoi district of Meghalaya, India. The collection was done using brush and forceps or handpicking and was preserved at 80% alcohol in the laboratory for further studies. All the type specimens (Holotype & Paratypes) of this study are deposited in the national repository of Zoological Survey of India at the North Eastern Regional Centre, Shillong (ZSI, NERCS), Meghalaya, India. Voucher specimens are preserved in the research collection of entomology laboratory, Department of Zoology, North-Eastern Hill University (NEHU), Shillong, Meghalaya, India.
Leica Stereo Zoom microscope S8AP0 fitted with GT 5.0 camera and mosaic V.2 photographic software was used to take the micrographs of the samples. Measurements were taken on the micrographs using Image J software (2018 version) and were also cross checked with the ocular micrometer fitted with the microscope.
Morphological studies of the soldier and worker castes and also all measurements, terminologies and indices were based on Roonwal & Chhotani (1989). Identification of the species was done following the available literature of Ahmad (1965), Chhotani (1997), andSyaukani &Thompson (2011).

Description
Imago: Unknown Soldier (Images 1-9, Table 1): Monomorphic. Head is pear shaped without rostrum and slightly constricted behind antennae. In colouration, head brown to rusty brown (in middle & posterior portion) to dark smoky brown (in anterior portion and lateral posterior ends). In dorsal profile, head weakly depressed behind rostrum, faintly concave, posterior margin roundly convex, two long bristles present on posterior end of head capsule. Fontanelle gland and tube visible. Rostrum cylindrical and darker than head with reddish-brown (proximal portion) to dark reddish-brown (distal portion) in colour. Tip portion with four long bristles and somewhat hyaline at end. Rostrum length usually more than the half of head length without rostrum and in some cases less than or equal to ¾ of head length without rostrum. Mandible vestigial with prominent long apical processes. Length of spine like apical processes slightly varies among the soldiers and right mandible without any minute tooth. Antennae generally 14 segmented (sometimes 13 segmented) and yellowish-brown to brown in colour. Segments vary in length. In 13 segmented ones, 2 nd shortest, 3 rd twice as long as 2 nd , 3 rd longer than 4 th and 5 th , 5 th longer than 4 th . In 14 segmented ones, 2 nd shortest or subequal to 3 rd , 4 th longer than 3 rd (sometimes 3 rd longer than 4 th ). Pronotum saddle shaped, indistinctly emarginated anteriorly and posteriorly. In colour, pale brown to brown. Anterior lobe darker than posterior and minute hairs present on anterior margin. Legs pale brown to straw in colour. Abdominal tergites pale brown in colour with long bristles on posterior tergites; sternites brownish-yellow in colour with long and short bristles.
Worker: Dimorphic. Worker major (Images 10-19; Table 2): Head subsquarish in shape; light brown with yellowish tinge to dark brown in colour and fairly pilose. Epicranial Y-suture distinct. Fontanelle plate prominent, oval. Postclypeus swollen, hairy and divided into two equal halves by the median suture. In length, less than half of its width. Antennae pale yellow to pale yellowish brown in colour and 14-15 segmented. In 14 segmented ones, 4 th shortest, 2 nd subequal to 3 rd or longer than 2 nd and 3 rd . In 15 segmented ones, 3 rd shortest or subequal to 4 th , 2 nd longer or subequal to 4 th . Mandibles with apical and 2-3 marginal teeth. Left mandible with prominent apical and 3 marginal teeth. Apical tooth and 1 st marginal tooth form an acute angle between them. Posterior margin of 1 st marginal slightly sinuate. Second and third marginal teeth small and prominent. Third marginal slightly longer than second and separated by wide U-shaped gap from molar prominence. Molar plate with four prominent ridges. Right mandible with 1 apical and 2 marginal teeth. Apical and first marginal teeth slightly boarder than left mandible ones. Apical tooth and 1 st marginal tooth form an obtuse angle between them. Second marginal tooth small, with a blunt apex, posterior edge nearly straight. Molar plate with 10 well developed prominent ridges. Inner layer of molar plate undeveloped and proximal notch of molar plate weakly developed. Thorax pale yellowish in colour. Pronotum saddle shaped, faintly emarginated at anterior and indistinctly emarginated at posterior. In colouration, light brown to brown and slightly lighter than colour of head. Anterior lobe darker than posterior and minute hairs present on anterior margin along with two long bristles on lateral sides each. Legs straw in colour. Abdominal tergites pale brown in colour with long bristles only on posterior tergites; sternites brownish-yellow in colour with long and short bristles.
Worker minor (Images 20-28; Table 2): Similar with worker major but smaller in size. Antenna only 14 segmented, 4 shortest, 2 subequal to 3 or longer than 3. Mandibles with apical and 2-3 marginal teeth, smaller in size than worker major. Apical and first marginal teeth less pointed than in worker major. Left mandible with apical and 3 marginal teeth, prominent. Apical tooth slightly shorter than 1 st marginal tooth with an acute angle between them. Posterior margin of 1 st marginal slightly sinuate. Second and third marginal small and prominent. Second marginal tooth broader than the left mandible ones of worker major. Third marginal slightly longer than second and separated by V-shaped gap from molar prominence. Molar plate with four prominent ridges. Right mandible with 1 apical and 2 marginal tooth. Apical tooth shorter and pointed than the 1 st marginal and form an obtuse angle between them. Second marginal tooth small with a blunt apex, posterior edge nearly straight. Molar plate with six well developed prominent ridges.

Comparison
The termite species Bulbitermes debadiliporum sp. nov., in its morphological characteristics and morphometrics ( Table 1 and 2) of the soldier and worker castes, shows slight similarity with other Bulbitermes J TT species of Indian region (Chhotani 1997), Thailand (Ahmad 1965) and Sumatra (Syaukani & Thompson 2011) but differ significantly in the key taxonomic characteristics which separate this species from the rest as a new Bulbitermes species.
Bulbitermes debadiliporum is closely related to B. prabhae in its morphological characteristics. But, the soldiers of B. debadiliporum have two long hairs on the head prosteriorly whereas B. prabhae without hairs. Antennae are 14 segmented in B. prabahe where segment 3 rd is longer than 4 th whereas 13-14 segmented in B. debadiliporum with segment 3 rd shorter than 4 th in 14 segmented antennae. No minute inconspicuous tooth observed below the tip of the apical process of the right mandibles in B. debadiliporum unlike B. prabhae. Morphometrics of soldier such as head length with and without rostrum, head width and rostrum length etc. are also vary slightly between the species.

Etymology
The name of this species is given in the honor of the first authors' mother Mrs. Deba Das and father Mr. Dilip Das.

Bioecology
Bulbitermes is primarily an arboreal nester genus that build stercoral carton nest of round or elongate shapes on the tree trunks, branches or in bushes (Weesner 1965;Lommen et al. 2004). They also live in wood nest (Arumugam et al. 2018). In case of the species B. debadiliporum, studied samples were collected from stercoral carton nest found inside the trunk of dead standing betelnut and dry bamboo. The trunk of the betelnut plant was eaten up completely from inside where the carton nest was located and it was somewhat elongated in shape. In dry bamboo tree, soldiers and workers were found foraging, but could not locate their nest. Due to their preference to feed on dead wood materials, B. debadiliporum may fall under the feeding group II.

DISCUSSION
Bulbitermes debadiliporum sp. nov. stands as a separate species from other Bulbitermes species due to its distinct morphological features. The soldier castes of the species have 13-14 segmented antennae along with significant variations in other morphological characteristics such as total body length, head length with and without rostrum, head width, rostrum length, rostrum length and head length index, head width at constriction, head width at constriction and head width index, head height, pronotum length and width etc. with other related Bulbitermes species from Indian and other Oriental regions. On the other hand, the worker caste of the species also shows distinct morphological features with 14-15 segmented antennae along with its dimorphic occurrence (workers major and minor). With the differences in number of antennal segments and morphometrics, workers major, and minor also differ in their molar plate ridges (10 molar ridges in workers major and 6 in workers minor) of the left mandibles. Dimorphism among the soldier and worker castes of Nastutitermitinae is not uncommon as many genera comprise of dimorphic soldier and worker caste (Chhotani 1997). Bulbitermes species with dimorphic workers also were reported from Malayasia earlier. But, among the Bulbitermes species from Indian region, the dimorphic worker caste is reported for the first time in B. debadiliporum. Besides, other morphological characters in worker caste such as head length and width, pronotum length and width etc. of B. debadiliporum also vary significantly with other related Bulbitermes species as discussed above. Thus, we propose this species Bulbitermes debadiliporum as a new Bulbitermes species from Meghalaya, India.

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