(Figs. 1–11)
Distribution. India (Kerala)
Host plants. Drynaria quercifolia (L.) (Polypodiaceae)
Description.General colour shining yellowish brown. Each elytron with four black spots: one on humerus, three along middle arranged in line (Fig. 3). Basal six antennomeres translucent yellowish brown or slightly darker, rest five black. Apex of last antennomere slightly yellowish. All tibiae distally darker than proximally. All tarsi dark brown to piceous.
Frons and vertex form slightly convex line in lateral view. Vertex shining, moderately convex, distinctly punctate with a mixture of fine to moderate sized punctures. Antennal calli oblique, longer than wide, narrowly raised along middle, margin with vertex as well as margin with antennal socket much lower than middle region. Midfrontal longitudinal depression does not pass beyond lower margin of antennal socket. Frontal ridge shiny, extremely minutely punctate with a very fine, sharp, indistinct carina along middle, either side of this carina being slightly depressed (Fig. 1). Maxillary palpus with apical palpomere two times as long as preapical.
Third antennomere distinctly longer than second, fourth subequal to or shorter than third; fifth slightly but distinctly longer than fourth; sixth slightly longer than half of fifth; seventh subequal to fifth in length; eighth smaller than seventh and ninth separately; tenth nearly as long as wide, shorter or subequal to ninth; eleventh two times as long as tenth. Thickness and length of distal antennomeres vary.
Pronotum proximally distinctly narrower than distally. Lateral margins weakly curved. Anterolateral callosity moderately high, forming sharp obtuse denticle at pore. Disc shiny, covered with a mixture of variously sized punctures. Punctation sparse on lateral sides. Antebasal transverse impression distinct on either ends, indistinct in middle, punctate throughout. Scutellum shiny, extremely minutely punctate, apex narrowly rounded, slightly longer than broad.
Elytron with well developed humeral callus, with depression posteriorly, maximum width at anterior 1 / 4. Disc shiny, punctures bold and interstices slightly convex in proximal region. Punctures turn indistinct posteriorly. Interstices with a mixture of small to minute punctures. Width of interstices in anterior half vary from two to four times diameter of a puncture. Epipleuron oblique, not reaching apex.
Metatibia straight in lateral view, slightly curved from dorsal view. Dorsally convex in
proximal 1 / 5 to 1 / 4, concave in distal 1 / 3 to 2 / 5, rest of surface flat. Metatibial spur almost equal to claw in length.
Posterior margin of last abdominal sternite in male distinctly bisinuate with a distinct lobe in middle (Fig. 4). Median lobe of aedeagus gently curved in lateral view (Fig. 6). Ventral side convex, slightly depressed at apex, almost parallel sided (Fig. 5). Dorsal opening covered by a single lamina, raised and sclerotised along middle (Fig. 7). Arms of tegmen shorter than stem (Fig. 8). Receptacle of spermatheca longer than pump, internal side more convex than external side, oblong, two times longer than wide with maximum width below middle. Pump with horizontal part subequal to vertical part. Pump and receptacle differentiated by a rim. Pump not narrowed to apex. Duct nearly twice as long as receptacle (Fig. 9). Vaginal palpus with membranous part in middle shorter than sclerotized part anteriorly and posteriorly. Anterior sclerotization slightly longer than posterior sclerotization. Apex transparent, posterior sclerotization deeply emarginate at apex, sides almost parallel in distal half; lateral margin forms indistinct angle with medial margin (Fig. 10). Tignum slightly curved and slightly widened proximally, narrowed preapically, sclerotized part of apex slightly widened (Fig. 11).
Measurements (all values in mm; n= 10). Length 2.85–3.95 (3.55); width 1.95–2.60 (2.38); length of pronotum 0.73–1.20 (1.00); width of pronotum 1.25–1.85 (1.64); width across eyes 0.73–1.05 (0.95); distance between eyes 0.35–0.53 (0.46); distance between antennal sockets 0.11–0.14 (0.13); length of aedeagus 1.10; length of vaginal palpus 0.56; length of receptacle 0.12.
Types. Holotype ɗ. Labels 1) India: Kerala Meppady 26. IV. 2002 Prathapan Coll. 2) Phaelota jacobyi sp. nov. Prathapan & Viraktamath, 2003 3) Holotype (BMNH).
Paratypes: 9 ɗ, 2 Ψ, same data as holotype (1 NHMB, 4 PKDC, 4 PNC, 2 USNM). 4 ɗ, 4 Ψ, same data as holotype except the date 18.IV. 2003 (4 PKDC, 2 PNC, 2 UASB); 2 ɗ, same data as above except the locality Ponmudi and the date 10.viii. 2003 and 17.viii. 2003 respectively (2 PKDC).
Etymology. This species is named after Martin Jacoby who laid the foundations of Oriental Leaf beetle taxonomy.
Remarks. P. jacobyi is the only yellowish species of Phaelota while others are reddish. Spots on elytron in P. jacobyi is consistent unlike in P. vaishakha where the colour is highly variable. Stronger pronotal punctures and longer prothorax are the other features which make it unique. Presence of carina along middle of frons (absent in P. sindhoori and P. vaishakha) differentiate it from other Indian species.