Two new species of army ants of the Aenictus ceylonicus group (Hymenoptera: Formicidae) from Kerala, India

: The genus Aenictus Shuckard is a diverse group of army ants in the Old World tropics and subtropics. Herein, two new species from India ( Aenictus kodungallurensis and Aenictus malakkaparensis ) belonging to Aenictus ceylonicus group were discovered from Kerala, India. An updated key to the Aenictus ceylonicus species group from southern Asia is presented.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print) Aenictus Shuckard 1840, belonging to the subfamily Dorylinae of the family Formicidae, is one of the true army ant genera occurring throughout Africa and in tropical and subtropical areas from India, Middle-east, southern China, Taiwan, Japan, Afghanistan, Armenia, southern Asia to New Guinea and Australia (Gotwald 1995;Shattuck 1999Shattuck , 2008Jaitrong & Yamane 2013). The genus Aenictus Shuckard, is the most diverse among all 18 genera of the monophyletic army ant subfamily Dorylinae (Brady et al. 2014) with 187 valid species and 30 valid subspecies (Bolton 2020). In the present paper we deal with the largest species group, the Aenictus ceylonicus Mayr group that has been revised in detail by Jaitrong & Yamane (2013). The group contains 23 species distributed in southern Asia. Two new species based on the worker caste are described here. Morphological and bionomic information is presented for each species. A key to the species is given. Most of the species of this species group have more or less limited distribution ranges. This may be due to the poor dispersal ability generally seen among the Aenictus species, in which the propagule (reproductive unit) is an apterous queen plus accompanying workers (Jaitrong & Yamane 2013).

Materials and Methods
The specimens were collected using hand picking method. The taxonomic analysis was done using a Labomed stereo zoom microscope. Optika Litevision stereozoom microscope was used to take images and measurements. Images taken were subsequently cleaned as per the requirement for Adobe Photoshop CC 2017. Images of whole ants and micro sculpture of parts were obtained using ZESS scanning electron microscope. Measurements and indices follow Jaitrong & Yamane (2013). Taxonomy follow Bolton (1994), Jaitrong & Yamane (2011 and Bharti et al. (2012). Holotype is deposited at the Zoological Survey of India Western Ghats Regional Centre (ZSIWGRC), Kozhikode, Kerala, India.
Morphological terminology for measurements (given

Diagnosis:
Jaitrong & Yamane (2011) defined this species group as follows: Antenna 10-segmented; scape reaching or extending beyond half of head length, but not reaching the occipital corner of head in full-face view. Mandible linear; it's basal and lateral margins almost parallel; masticatory margin with large apical tooth followed by medium-sized subapical tooth; between subapical tooth and basal tooth 0-6 small denticles present. With mandibles closed, a gap is present between mandibles and anterior margin of clypeus. Anterior clypeal margin weakly concave or almost straight, lacking denticles. Frontal carina short and thin, reaching or slightly extending beyond the level of posterior margin of torulus; anterior curved extension of frontal carina reaching or extend ing beyond the level of anterior clypeal margin in full-face view; parafrontal ridge absent. Promesonotum usually convex dorsally and sloping gradually to propodeum. Subpetiolar process developed. Head and first gastral tergite smooth and shiny. Body yellowish, reddish or dark brown; typhlatta spot absent.

Worker description
Head: Head in full-face view sub rectangular, slightly longer than broad, sides convex, posterior margin almost straight; anterior part of head is broader than posterior part. Antennae with 10 segments, with ill-defined three segmented club and scape is short reaching almost 1/2 of head length. Anterior clypeal margin almost straight or feebly concave. Mandibles with basal margin edentate, masticatory margin of mandible with large acute apical tooth followed by a medium-sized subapical tooth, three denticles, and a medium-sized basal tooth.
Mesosome: Promesonotum convex dorsally and sloping gradually to metanotal groove; mesopleuron relatively long, clearly demarcated from metapleuron by a groove. Propodeum in profile with almost straight dorsal outline; propodeal junction angulate; declivity of propodeum flat, with blunt lateral carinae but not demarcated basally by a transverse carina.
Petiole, Post Petiole. Petiole longer than high, node short, elevated posteriorly and dorsal outline convex; sub petiolar process low and short, with anterior and posterior corners bluntly angulated and its ventral outline convex. Postpetiole clearly smaller than petiole, its dorsal outline convex.
Head, antenna and gaster entirely smooth and shiny; mandible finely striate with long decumbent hairs. Promesonotum smooth and shiny except for anteriormost portion punctate; mesopleuron with slightly irregular rugae; metapleuron, and propodeum wrinkled and reticulate. Petiole and postpetiole entirely reticulate except small area on dorsa smooth and shiny. Head and mesosoma dorsally with relatively sparse standing hairs. Legs with dense long decumbent hairs.
Etymology: The species name is after the type locality, Malakkapara.
Distribution: Known only from the type locality in Kerala.
Remarks: Aenictus malakkaparensis sp. nov. is similar to Aenictus appressipilosus from which it can be fairly separated by a combination of characters. Aenictus appressipilosus have two long standing hairs mixed with few short appressed hairs on the vertex and has a few appressed hairs mixed with few decumbent hairs on promesonotum whereas in Aenictus malakkaparensis sp. nov. two long standing hairs are absent and its sub petiolar process is low and short, with anterior and posterior corners bluntly angulated and the ventral outline convex.

Worker description
Head: Head in full-face view sub rectangular, slightly longer than broad, sides convex, posterior margin almost straight; anterior part of head is broader than posterior part. Antennae with 10 segments, with ill-defined three segmented club and scape reaching almost 2/3 of head length. Anterior clypeal margin almost straight or feebly concave. Mandibles with basal margin edentate, masticatory margin of mandible with a large acute apical tooth followed by a medium-sized subapical tooth, two denticles, and a medium-sized basal tooth.
Mesosome: Promesonotum convex dorsally and sloping gradually to metanotal groove; mesopleuron relatively long, clearly demarcated from metapleuron by a groove. Propodeum in profile with almost straight dorsal outline; propodeal junction angulate; declivity of propodeum flat, with blunt lateral carinae but not demarcated basally by a transverse carina.
Petiole longer than high, node short, elevated posteriorly and dorsal outline convex; subpetiolar process low and subrectangular with anteroventral and posteroventral corners bluntly angulated and margin between the corners straight to feebly concave. Postpetiole clearly smaller than petiole, its dorsal outline convex.
Head, antenna and gaster entirely smooth and shiny; mandible finely striate. Promesonotum smooth and shiny except for anterior most portion punctate; mesopleuron with slightly irregular rugae; metapleuron, and propodeum wrinkled and reticulate. Petiole and postpetiole entirely reticulate except small area on dorsa smooth and shiny. Head and mesosoma dorsally with relatively dense standing hairs mixed with relatively dense decumbent hairs. Legs with dense long decumbent hairs. Mesosoma, petiole and postpetiole reddish-brown; head, antennal scape, gaster and legs yellowish-brown.
Etymology: The species name is after the type locality, Kodungallur.

Distribution: Known only from the type locality in Kerala.
Bionomics: So far, this species has been known only from Kodungallur.
Remarks: Aenictus kodungallurensis sp. nov. is collected from coastal area with loose coastal alluvium soil by handpicking method. Aeniictus kodungallurensis sp. nov. is smaller in size than Aenictus malakkaparensis sp nov. The antennal scape of Aenictus malakkaparensis sp nov. is shorter compared to Aenictus kodungallurensis sp. nov. The shape of subpetiolar process is also different, the ventral margine between corners is straight or feebly concave in Aenictus kodungallurensis sp. nov. but it is convex in Aenictus malakkaparensis sp. nov. Head and mesosome of Aenictus kodungallurensis sp. nov. is covered with dense hairs but in case of Aenictus malakkaparensis sp. nov. head and mesosome is only covered by sparse hairs.

Discussion
Aenictus kodungallurensis sp. nov. and Aenictus malakkaparensis sp. nov. are members of A. ceylonicus group, which is a unique group easily separated from the other groups by the following characteristics: mandible linear; a gap is present between mandibles and anterior margin of clypeus when mandibles are closed; anterior clypeal margin almost straight or feebly concave, lacking denticles. The A. ceylonicus group occurs in the Oriental, Indo-Australian and Australasian regions (Wilson 1964; Shattuck 2008; Jaitrong & Yamane 2011). A. kodungallurensis sp. nov. and A. malakkaparensis sp. nov. are the only members of Aenictus ceylonicus group reported from Kerala. Both the species are collected from ground by hand picking method. Major difference between both the species is in the structure of sub petiolar process and the promesonotum of A. kodungallurensis is covered with dense decumbent hairs. A. kodungallurensis sp. nov. is collected from a mixed vegetation area in coastal region with coastal alluvium soil whereas Aenictus malakkaparensis sp. nov. is collected from a hilly area with silty loam at an elevation of 1,016 m.

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