Armyworms and cutworms are agricultural pests that can occasionally damage agricultural crops significantly. Armyworm, Leucania Ochsenheimer is one of the most significant pests on graminaceous crops, which is widespread in Africa, Australia, Asia, and the Middle East. A thorough comparative study on the taxonomy of species within the genus Leucania Ochsenheimer has identified two recognized species: L. loreyi and L. roseilinea. Detailed discussions include morphological characteristics such as frons, vertex, antennae, labial palpi, compound eyes, ocelli, proboscis, wing venation, and male and female genital features, along with identification keys supported by photographs and illustrations. Armyworm species are known to be polyphagous and are commonly found in the Indian subcontinent. The taxonomic research presented here lays the foundation for future monitoring of species identities and potential outbreaks affecting cereal crops.

Armyworm, Leucania loreyi, Taxonomy, Leucanini, Male genitalia.

Armyworms (Lepidoptera: Noctuidae) with high larval populations have become significant pests globally. These armyworms are polyphagous, primarily feeds on cereals, pastures, and forage crops (Rungs, 1955). Although species from the genera Mythimna and Spodoptera are widely reported as armyworms or cutworms, information on outbreak occurrences of other genera remains unclear. In Australia, the sugarcane armyworm, Leucania loreyi, is reported as an armyworm infesting graminaceous crops (Edwards, 1992). During the revision of the common names list of Australian insects, it was determined that all examined specimens from Australia belonged to Leucania loreyimima rather than Leucania loreyi (Gay, 1966).

The maize caterpillar, Leucania loreyi (Duponchel, 1827) (Noctuidae), is commonly known as the Loreyi leaf worm, cosmopolitan rice armyworm, rice cutworm, cereal armyworm, or false armyworm (Hill, 1988; Jalaeian et al., 2017). This noctuid is a native species of East Asia (Nam et al., 2020) and is a pest of grain crops in Africa, Australia, the Near East, and the Middle East, where it undergoes multiple generations each year (Calora, 1966; Chandler & Benson, 1991). This pest has been reported on several gramineous hosts, including nine Poaceae species (Arundo donax, Avena sativa, Oryza sativa, Pennisetum purpureum, Saccharum officinarum, Sorghum bicolor, Triticum aestivum, Triticum durum, and Zea mays), two Solanaceae species (Capsicum spp. and Nicotiana tabacum), and one Fabaceae species (Cicer arietinum) (Hill et al., 1997; Ikincisoy & Kornosor 1996; Vieira, 2008). Kornosor (1999) noted that L. loreyi primarily infests maize and significantly reduces yields when attacks occur just before silking and pollination. In Egypt, the fecundity of female moths is highest when the larvae feed on maize (El-sharif, 1972). Additionally, Guo et al. (2003) reported that L. loreyi often occurs alongside the closely related species Mythimna separata (Walker, 1865), causing considerable damage to host plants. The caterpillars bore into the plants and attack the developing flower spikes. Moreover, Holloway (1989) reported that L. loreyi caused significant crop production losses. His study, based on Bornean specimens, divided the genus Mythimna into several subgenera: Aletia, Pseudaletia, Acantholeucania, and Leucania. In contrast, Edwards (1996) treated Leucania as a distinct genus, placing Acantholeucania under the subgenus Leucania and Pseudaletia under the subgenus Mythimna.

Leucania Ochsenheimer, 1816, is a globally distributed genus in the family Noctuidae, comprising up to 350 valid species, with approximately one-third of this diversity found exclusively in the New World (Lafontaine & Schmidt 2010; Adams, 2001; Cocco et al., 2019; Dolibaina et al., 2019). The taxonomy of the genus has been thoroughly studied in the Neotropical region (Adams, 2001), but this is not the case for South and Southeast Asia (Kalleshwaraswamy et al., 2023). The Leucania-complex is an assemblage of species belonging to the subfamily Hadeninae of the family Noctuidae. The moths are superficially very similar, and may be described as average-sized, hairy-eyed moths without bright coloration: they are usually pale ochreous white to deepochreous, striate with darker transverse markings usually inconspicuous and usually reduced to dots (Calora, 1966). Adults in this group are cryptically coloured, with phenotypes resembling dried grasses, which are their natural habitats (Adams, 2001). The species are difficult to distinguish based on colour or superficial pattern. As a result, species have been poorly characterized by authors, are frequently misidentified, and many synonyms have been proposed inadvertently. To the best of our knowledge, no taxonomic studies have been conducted on the moth genus Leucania (Noctuidae: Hadeninae) in India, excepting for the work of Moore (1881). To address these taxonomic challenges and to understand the biology of these pests, there was a need to clarify the species identity and composition. Hence, we conducted extensive surveys and collections of Leucania moths from Karnataka, and the findings are presented in this paper.

The extensive collection-cum-survey tours were made from different locations of Karnataka, representing major host plants growing areas of state. A 200W mercury vapor lamp was used as the light source, with a white cloth background (10 ft × 6 ft) in the fields to collect adult moths. The moths attracted to the light trap were collected, and their processing and preservation were carried out following the standard procedures for Lepidoptera. External morphological structures were studied using a Nikon SMZ 1000 Stereo-zoom microscope.  The Leucania were identified based on characters like orbicular and reniform spot, attributes of male genitalia such as the shape of uncus, tegumen, valve, ampulla, cucullus, juxta, aedeagus and also with female genitalia characters like corpus bursae, ductus bursae, signum, ventral plate, anterior and posterior apophyses.  

To prepare genitalia slides, the adults were sexed based on wing coupling i.e., males having a single frenulum and females possessing two or three frenular spines. The abdomen was detached from the thorax using a needle and forceps, as cutting the last few segments often damaged the genital structures in both males and females. The separated abdomen was then placed in a cavity block containing a 10% KOH solution and left overnight. Afterward, the abdomen was washed with distilled water in a cavity block to remove any excess KOH. It was then placed in another cavity block containing 10% ethanol. Using fine forceps, the genitalia were carefully separated from the abdomen. The genital structures were then placed on a clear microscope slide in 98% pure glycerol, covered with a cover slip, and subsequently photographed and identified. The aedeagus was detached from the main genitalia while ensuring that the juxta and transtilla remained intact. Later, vesica was everted from the aedeagus by using syringe. Aedeagus and female genitalia were stained with acid fuchsin or chlorazol black for a few minutes. Specimens were initially identified based on their genitalia structures with reference to relevant literature (Adams, 2001; Calora, 1966; Edwards, 1992; Moore, 1881; Poole, 1989; Yoshimatsu, 1994). The terminologies of Klots (1970) were used to describe the genitalia. After examining the specimen parts, they were transferred into a micro-vial containing 98% glycerol and pinned beneath the corresponding specimen. The forewing length was measured from the tip of the wing apex to the outer edge of the tegula. Photography of adult moths was made with the help of a canon 80D digital camera with 100mm lens. Photographs of the male and female genitalia structures were taken using a Leica 25°C auto-montage microscope mounted with a Leica DFC 450 camerain the Taxonomy Laboratory. All images were processed using Adobe Photoshop®CS6. The voucher specimens have been deposited in the insect collection museum, Department of Entomology, University of Agricultural Sciences, GKVK, Bengaluru. 

Genus Leucania Ochsenheimer, 1861

Ochsenheimer, 1816, Eur. Schmett, 1816: 81

Type species: Leucania comma Linnaeus, 1761

Distribution: Found worldwide, except in the Australian region.

Diagnosis: Palpi obliquely upturned, with the 2nd joint roughly scaled and the 3rd joint prominent, short, naked, and depressed. The proboscis is fully formed, and the eyes are hairy. Antennae are minutely ciliated in males. The head is not deeply retracted into the thorax, which is smoothly scaled. The abdomen with scarcely a trace of dorsal tufts on the basal segments. The tibia and tarsi are covered with short hairs.

Remarks: Genus Leucania was proposed by Ochsenheimer in 1816, on type species comma Linnaeus. Hampson (1894) studied 47 species under this genus from different localities of British India. Fronclemont (1951) studied species of Leucania group of North America. In 1962, Sugi studied Leucania insecuta Walker and Leucania striata Leech as two distinct species from China. Two species of genus, Leucania viz., L. loreyi (Duponchel, 1827) and L. roseilinea (Walker, 1862) have been collected from different localities of Southern Karnataka of India for external genital attributes.

Table 1: A checklist of armyworm genus Leucania Ochsenheimer, 1816 from India.

(Chandra et al., 2021; Hampson, 1984) (Anonymous, 2024; URL: https://www.mothsofindia.org/leucania-loreyi)

Key to species of Leucania

1. Forewing greyish brown with dark stria at middle, ventroposterior process of valvula acutely curved posteriorly………………….……….…loreyi

• Forewing reddish brown with prominent white line at middle, ventroposterior process of valvula absent…………….………………….….roseilinea

Leucania loreyi (Duponchel, 1827) (Fig. 1)

Noctua loreyi Duponchel, 1827: 81.

Leucania collecta Walker, 1856:105.

Acantho Leucania loreyi Inque and Sugi, 1958: 474.

Leucania loreyi Calora, 1966: 65.

Mythimna (Acantholeucania) loreyi Holloway, 1989, 89.

Leucania loreyi Poole, 1989, 582.

Leucania loreyi Sugi, 1992, 200. Yoshimatsu, 1993.

Description:Forewing pale brown with a dark stria below the median vein and the upper portion of the median vein pale brown. A small white spot is present at the end of the discal cell, followed by a fuscous area. The terminal line is marked by black spots on the interspaces, and the fringe is fuscous. The hindwing is whitish with pale brown veins. The terminal line is indicated by black spots on the interspaces, and the fringe is dull whitish.

Length of forewing: 17-19.2 mm (male) and 17.4-19.7 mm (female).

Male genitalia: Uncus moderately long, strongly curved ventrally on subbasal portion with hairs on distal 3/4. Tegumen long, moderately broad and almost straight in lateral view. Vinculum narrow and with short slender dorsal arm. Saccus rounded. Valva except cucullus slightly long with a long process at the ventroposterior portion and with membraneous posterior margin, costa gradually curved dorsally. Ampulla short, tapering, curved ventrally, with a small rounded process at the middle. Sacculus moderately broad. Valvula broad with broad membraneous area, the ventroposterior process strongly curved posteriorly on distal 1/4. Cucullus moderately long, semicircular, with rounded ventral margin and a few spines marginally, without coronal spine. Juxta was pentagonal shape. Aedeagus short bulged at tip, with the vesica being twice as long as the aedeagus and with a tubular diverticulum at middle, bearing a patch of small spines at tip of the diverticulum and a large spine near distal end.

Female genitalia: Ductus bursae sclerotised, curved dorsal at the middle with many longitudinal striae on anterior half, ostium bursae unmodified. Corpus bursae was rounded, appendix bursae short, small, membranous and projecting from anterior portion of ductus bursae. Apophyses anterior and apophyses posterior were moderately long. Papilla analis unmodified.

Materials examined: INDIA: Karnataka:2♂, Mandya V.C. Farm, 13.ix.2018, Basavaraj N. H.;3♂, Mandya V.C. Farm, 22.xi.2018, Basavaraj N. H.;2♂, Bengaluru, GKVK campus, 7.ii.2019, Basavaraj N. H.; 5♂, Bengaluru, GKVK campus, 9.ii.2019, Basavaraj N. H.; 2♂, Bengaluru, GKVK campus, 25.i.2019, Basavaraj N. H.

Remarks: In male genitalia valvula with long ventroposterior process bent at distal portion. Sexual dimorphism absents. Semi-circular cuculls with ventral portion rounded with spines like structure, coronal spines absent, pentagonal juxta. This species may be confused with M. venalba Moore and M. roseilinea Walker, but it is larger and has a distinct white fleck at the discal end of CuA in the forewing cell. Unlike the other two species, L. loreyi lacks the postmedial costal brown mark on the forewing. Additionally, the hindwing margin often displays dark brown marks on the veins, which are rarely seen in the other two species.

Leucania roseilinea (Walker, 1862)(Fig. 2)

Leucania roseilinea Walker, 1862: 179.

Leucania compta Moore, 1881a, 336.

Leucania compta Hampson, 1894, 272.

Leucania roseilinea Poole, 1989:211; Hacker et al., 2002: 4.

Description: Forewing were pale brown, the veins white, median nervure prominent with expanded distal portion, beyond which is fuscous, pale brown striae on interspaces below veins, postmedial line is marked by black spots on the veins, and a pale brown triangular shade extends from the termen below the apex, terminal line represented by black spots on interspaces, fringe fuscous brown. Hindwing white with pale brown scales on subterminal area, fringe dull white.

Length of forewing: 12.9-14.3 mm (male) and 12-15.2 mm (female).

Male genitalia: Uncus long, slender, strongly curved ventrally on the subbasal portion. Tegumen slightly broad in lateral view. Vinculum with well curved dorsal arm, saccus broad and pointed at tip. Valva except cucullus with round ventral margin and rectangular corner on the ventroposterior portion, costa abruptly descending ventrally on the basal portion with a small haired rounded process at the end of costa. Ampulla short and hooked ventrally, sacculus  broad, harpe very long with two small processes along the ventral margin, dorsal process of harpe long, slender and beyond the dorsal margin of costa. Valvula moderately broad membranous area and few long spines along ventral margin. Cucullus crescent shaped, without coronal spine and basal arm. Juxta nearly triangular. Aedeagus with a long slender ventral plate bearing a thorn, vesica long, about three times as long as aedeagus when everted, bearing dense spinules on entire surface of distal ¾.

A. Adult male; B. Male gennitalia; C. Aedeagus; D. Adult female; E. Female genitalia

Fig. 1. Leucania loreyi (Duponchel, 1827).

A. Adult male; B. Male gennitalia; C. Aedeagus; D. Adult female; E. Female genitalia.

Fig. 2. Leucaniaroseilinea (Walker, 1862).

Female genitalia: Ductus bursae sclerotised strongly curved ventrally near corpus bursae, with many longitudinal striae on anterior portion, ostium bursae narrow. Corpus bursae rounded, appendix bursae long, tubular, sclerotised with membraneous distal portion, waved on basal 2/3. Apophyses anterior and apophyses posterior were moderately long. Papilla analis unmodified.

Materials examined: INDIA: Karnataka: 2♀, Mysore, Hunasur, 10.xii.2018, Basavaraj N. H.; 3♂, Mysore, Hunasur, 10.xii.2018, Basavaraj N. H.

Remarks: This species has been reported for the first time from Karnataka state. In this species white colour median nervure prominent with expanded distal portion on forewing. Adult were small compared to Leucania loreyi. Cucullus crescent shaped, without coronal spine and basal arm. Juxta was nearly triangular.

Moreover, the misidentifications are linked with the fact that all species have a similar habitus. There is a need to carry out systematic studies on the genus Mythimnaand Leucania. Earlier authors both genus Mythimna and Leucania were grouped together.  Few authors (Hampson, 1894) mentioned these two genera are grouped together and, in others (Edwards, 1992; Holloway, 1989; Yoshimatsu, 1994), they are kept separately. According to Rungs (1955) and Lafontaine & Schmidt (2010) described Leucania spp. do not possess a corona on the cucullus while Mythimna spp. have a corona. Moore (1881) described 20 new species from India under the genus Leucania, accompanied by a hand-drawn plate in his initial description. Additionally, Yoshimatsu (1994) provided a genitalia description and confirmed the findings. The male genitalia of the available specimens were compared with reference illustrations of Leucania species provided by Adams (2001); Calora (1966); Edwards (1992); Yoshimatsu (1994). The specimens were found to be identical and were confirmed as Leucania loreyi and L. roseilinea. Species identification was further validated through morphological examination and male genitalia comparison. Robinson et al. (2001) reported  L. roseilinea on rice, with its distribution recorded in states such as Nagaland, Odisha (Ganjam), and Tamil Nadu (Nilgiris) (Chandra et al., 2021; Hampson, 1984). L. loreyi is widely distributed across India (Hampson, 1984) and feeds on crops including chillies, sorghum, oats, and rice (Robinson et al., 2001; Sharma et al., 2002). However, this study confirms the presence of L. loreyi and L. roseilinea in Karnataka as well. In India, no species of Leucania has yet been reported to occur in outbreak form. One possible reason for this could be that field entomologists have mistakenly identified them as Mythimna without proper taxonomic identification (Kalleshwaraswamy et al., 2023).

Advancements in molecular techniques, integrative taxonomy, and ecological studies offer promising avenues for the taxonomic identification of Leucania species (Lepidoptera: Noctuidae). However, comprehensive surveys and extensive specimen collection across various states of India, including additional locations within Karnataka, are essential to enhance our understanding of species diversity and distribution. Given that larvae are the primary damaging stage responsible for economic losses, their accurate taxonomic identification is crucial for developing effective pest management strategies.