Meliboeus morawitzi Semenov, 1905

Prokhorov, Alexey V. & Gubin, Oleksandr I., 2019, Description of the larva of Meliboeus morawitzi (Semenov, 1905) (Coleoptera: Buprestidae), Zootaxa 4668 (1), pp. 115-125 : 117-122

Meliboeus morawitzi Semenov, 1905

Material studied. Ukraine: Donetsk Region: Khomutovskyi Steppe Nature Reserve , 47.2995 N 38.1809 E, in roots of Artemisia marschalliana , 13.09.2017, 10 mature and premature larvae (O. Gubin) .

Measurements. Body length 14.3–22.0 mm; width of prothorax 1.7–1.9 mm.

Mature larva. Body of usual agrilinoid type ( Fig. 9 ), flattened, whitish-yellow with slightly enlarged prothorax, prothoracic plates bearing two yellowish, weakly sclerotized pronotal grooves and single prosternal groove, mesothoracic and abdominal spiracles and heavily sclerotized two-segmented terminal processes (with one inner ledge). All body segments almost glabrous with exception of the last segment bearing long setae on the sides; single microsetae are barely visible on the head sides.

Head and mouthparts. Epistome ( Fig. 3 , 10 ) narrow, transversely widened, 5.4–5.5 times wider than long, with two pairs of epistomal sensilla medially, situated almost on one line; laterobasal angles weakly developed, strongly blunt. Anteclypeus 3 times wider than long. Labrum ( Fig. 4 , 11 ) with rounded anterior margin covered with numerous acute microsetae (the posterior margin of the microsetal area forms slightly wavy line); anterolateral corners ventrally on each side bears two long curved at base, blunt apically, flattened anterior setae whose bases inserted in special pockets ( Fig. 4 , 11 : vs). Dorsal anterior seta ( Fig. 4 , 11 : das) more than 2 times longer than dorsal posterior seta ( Fig. 4 , 11 : dps). Near the anterior ventral setae, but dorsally and closer to the middle of the labrum, there is one long apical anterolateral seta ( Fig. 4 , 11 : aals) on each side of the labrum whose bases are inserted in special pocket (their bases are in the line with the bases of anterior ventral setae). Median sensilla of the palatine sclerites of the labrum consist of long subapical seta (the longest seta of labrum) and two subbasal campaniform sensilla ( Fig. 4 : scs), which occupy the standard position (lower sensilla are at the level of the bases of dorsal posterior setae). Epipharynx covered with few microsetae arranged along median branches of palatine sclerites and curved towards median longitudinal axis of labrum. Antennae ( Fig. 5 , 13 ) two-segmented, 1st segment subcylindrical, at least 2 times as wide as long, with sclerotized lateral side, fringe of microspinulae around apex absent (unlike Agrilus ); the second segment rounded trapezoid, about 1,7 times as wide as long with sclerotized lateral side, bearing long trichosensillum ( Fig. 5 , 13 : ts) (it length exceeds the length of entire antenna together with sensory appendage), prominent and pointed sensory appendage ( Fig. 5 , 13 : sa) sitting on extended base (length of appendage is not less than the length of the second segment), 2 palmate sensilla ( Fig. 5 , 13 : ps) and 1–2 basiconic sensilla ( Fig. 5 , 13 : bs) at base of the sensory appendage. Mandibles ( Figs 14, 15 ) triangular, heavily sclerotized, with two blunt apical teeth, internal margin with penicillum ( Fig. 14 , upper arrow), consisting of numerous long microtrichia, external margin with seta ( Fig. 14 , lower arrow) located above dorsal articulation. Inner side of mandibles with blunt rib ending with small tooth which located at the base of apical tooth (on the opposite side from where the penicillum is located). Labio-maxillary complex ( Figs 12, 16, 17 ). Maxillae with membranous cardo ( Fig. 12 : c) bearing 2 setae nearly the same length (their length is not less than the length of the second segment of maxillary palpus). Stipes ( Fig. 12 : s) with sclerotized inner and outer sclerites, long seta apically at the base of mala, short seta anterolaterally, and campaniform sensillum at the level of the base of short seta but closer to the middle of stipes; sparse cilia are visible on anterior margin laterally and on inner side. The first segment of maxillary palpi ( Fig. 12 : mp1) slightly wider than long (with wide base), with well-sclerotized outer sclerite, long seta near anterolateral margin and campaniform sensillum below long seta (approximately at the middle of lateral margin of segment); anterolateral margin with few long cilia. The second segment ( Fig. 12 : mp1) 1.5 times as long as wide, with well-sclerotized outer and inner sclerites, campaniform sensillum along lateral margin, inner curved sensillum along internal margin, and sensory cones apically. Prementum ( Figs 6 ; 12, 16, 17 : p) nearly quadrate, with almost straight anterior margin and rounded lateral corners, externally with short microsetae forming narrow microsetal area along anterior margin, posterior border of this area slightly wavy, extending about 1/4 distance from anterior margin of prementum to imaginary line connecting the bases of apical setae of corner sclerites of prementum. Sclerotized mala ( Fig. 17 : ma) about 1.8–2.0 times as long as wide, with 2 long basiconic sensilla apically, 3 long setae externally, 3 short thick blunt setae internally and long seta at the base of mala internally. Internal surface of mala beneath thick blunt setae with curved cilia.

Thorax ( Figs 18–21 ). Prothorax is the widest part of the body, 1.5–1.6 times as wide as long, mesothorax 2 times as wide as long, metathorax 1.75 times as wide as long. Pronotal plate ( Fig. 18 ) slightly more strongly sclerotized around anterior third of the grooves forming almost triangular area of sclerotization (covered with dense microspinules); pronotal grooves ( Fig. 19 ) diverging towards the base of pronotum, well-sclerotized in central part. Prosternal plate ( Fig. 20 ) covered with dense microspinules around anterior part of the groove forming transversely elongated area of sclerotization; prosternal groove ( Fig. 21 ) well-sclerotized in central part. Mesothoracic spiracles ( Fig. 22 ) of agriloid circular type, located closer to ventral side of segment, moderately sclerotized, cribriform with numerous trabeculae.

Abdomen ( Figs 9 , 23, 24 ). The first seven abdominal segments longer than wide; the eighth segment almost quadrate; width of the ninth segment 1.6 times its length; the tenth segment triangular, with heavily sclerotized paired terminal processes apically. Apical part of terminal processes about 2 times as long as wide. The length of longest setae on the sides of last abdominal segment approximately equal to the length of apical part of the terminal processes ( Fig. 24 ). Abdominal spiracles ( Fig. 25 ) similar to mesothoracic spiracles but slightly smaller, situated in anterior quarter of the first seven segments, on the eighth segment they located closer to its middle.

Diagnosis. Mature larva of M. morawitzi differs from the larvae of other known Meliboeus species by its large size (14.3–22.0 mm, vs, 11.5– 14 mm in the others).

The M. morawitzi larva clearly differs from M. fulgidicollis larva by two pronotal grooves and the presence of anal pubescence ( M. fulgidicollis has one pronotal groove and anal segment without setae ( Bílý 1999)).

The M. morawitzi larva is similar to M. graminis larva by: presence of two pronotal grooves diverging to posterior margin of pronotum; the shape and structure of labrum. M. morawitzi larva can be distinguished from M. graminis larva ( Figs 7 , 26–31 ) by the following features: the shape of sclerotized field formed by microdenticles around pronotal grooves (in M. graminis , weakly pigmented field completely surrounds the grooves, transversely elongated areas of stronger sclerotization may be noticeable at anterior and posterior margins of the field; the anterior part of straight prosternal groove surrounded with oval or triangle field of sclerotization (in M. graminis , prosternal plate with groove clearly extended anteriorly ( Alexeev 1988), and with field of weak sclerotization posteriorly; the shape and structure of prementum (in M. graminis , prementum ( Fig. 7 , 31 ) with rounded anterior margin, microsetal area in shape of wide triangle, the lateral margins of which may be right angled or notched, and posterior border extending about half or third distance from anterior margin of prementum to imaginary line connecting the bases of apical setae of corner sclerites of prementum). Both species develop in wormwoods, although the larvae of M. graminis also recorded from? Centaurea spp.,? Clinopodium spp.,? Helichrysum spp. ( Alexeev 1988; Bílý 1999).

M. morawitzi larva is similar to M. parvulus larva by presence of two pronotal grooves more or less diverging to posterior margin of pronotum; it can be distinguished from the latter by shape of pronotal grooves and presence of sclerotized field in their anterior part (in M. parvulus , pronotal grooves close together in anterior half and weakly diverging and curved in posterior half, completely surrounded by very weakly sclerotized rounded field); the shape and structure of labrum (in M. parvulus , labrum with straight anterior margin and short bristles on external side of the labrum forming field of rounded-triangular shape); by structure of prementum (in M. parvulus , microsetal area of triangular shape, posterior border of this area extending about 3/4 distance from anterior margin of prementum to imaginary line connecting the bases of apical setae of corner sclerites of prementum). The larvae of these species develop in different plants; M. parvulus larvae were found in Carlina spp., Cousinia spp., Echinops spp.,? Eryngium spp. ( Alexeev 1988), Carduus spp., Cirsium spp., Onopordon spp. ( Bílý 1999), i.e., belonging to the tribe Cardueae . The comparision with the larva of M. parvulus was based on the description by Alexeev (1988: as amethystinus).

Morphologically the larva of M. morawitzi is similar to the larva of M. subulatus ( Figs 8 , 32–37 ); adults are also similar. M. morawitzi larva clearly differs from M. subulatus by structure of prementum (in M. subulatus , microsetae on external side of prementum forming rather wide microsetal area with deep median notch, ( Fig. 8 , 37 ), posterior border of microsetal area extending about half distance from anterior margin of prementum to imaginary line connecting the bases of apical setae of corner sclerites of prementum). The host plants of these species are different (larva of M. subulatus develops in tansy roots). The comparision with the larva of M. subulatus was based on the description by Bílý (1998) and on own material.

Note. Since Buprestis aeneicollis Villers, 1789 (= Coraebus fulgidicollis Lucas, 1846 ) was re-designated as a type species of the genus Meliboeus Deyrolle, 1864 ( Kubáň 2006) , subgeneric position of the species previously belonging to subgenus Meliboeus s. str. remains uncertain. This statement is based on the fact that pronotal plate of the larva of M. fulgidicollis bears only one groove while in other known species of the genus Meliboeus pronotal plate with two grooves. Genera whose larvae demonstrate both character states (single and double pronotal grooves) are so far unknown.

Figures

FIGURES 9–17. Meliboeus morawitzi (Semenov, 1905), mature larva. 9 Habitus, dorsal view; 10 Epistome with labrum, dorsal view; 11 Labrum, dorsal view (aals: apical anterolateral seta, das: dorsal anterior seta, dps: dorsal posterior seta, ss: subapical seta, vs: ventral seta); 12 Labio-maxillary complex, external surface (c: cardo, s: stipes, mp1: first segment of maxillary palpi, mp2 the second segment of maxillary palpi, p: prementum); 13 Right antenna, dorsolateral view (ts: trichosensillum, sa: sensory appendage, ps: palmate sensilla, bs: basiconic sensilla); 14 Right mandible, dorsal view (upper arrow shows the edge of penicillium, lower arrow shows the seta attachment); 15 Right mandible, lateral view (arrow shows the small tooth on the inner side of mandible); 16 Prementum, external surface; 17 Prementum and maxillary palp, internal surface (ma: mala, p: prementum).

FIGURES 3–8. Larvae of Meliboeus, details of structure. 3–6 M. morawitzi (Semenov, 1905), mature larva: 3 Epistome with labrum, dorsal view (l: labrum, ac: anteclypeus, es: epistomal sensilla); 4 Labrum, dorsal view (aals: apical anterolateral seta, das: dorsal anterior seta, dps: dorsal posterior seta, ss: subapical seta, vs: ventral seta); 5 Right antenna, dorsolateral view (ts: trichosensillum, sa: sensory appendage, ps: palmate sensilla, bs: basiconic sensilla); 6 Prementum with apical setae of corner sclerites and microsetal area; 7 Prementum of M. graminis (Panzer, 1799), 8 Prementum of M. subulatus (Morawitz, 1861).

FIGURES 18–21. Meliboeus morawitzi (Semenov, 1905), mature larva. 18 Pronotal plate of prothorax; 19 Pronotal grooves; 20 Prosternal plate of prothorax; 21 Prosternal groove.

FIGURES 22–25. Meliboeus morawitzi (Semenov, 1905), mature larva. 22 Mesothoracic spiracle; 23 Abdominal apex with terminal processes, dorsal view (setae not shown); 24 Terminal processes of anal segment, lateral view; 25 Abdominal spiracle (segment 2).

FIGURES 26–31. Meliboeus graminis (Panzer, 1799), mature larva. 26 Epistome with labrum, dorsal view; 27 Labrum, dorsal view; 28 Pronotal plate of prothorax; 29 Prosternal plate of prothorax; 30 Labio-maxillary complex, external surface; 31 Prementum, external surface.

FIGURES 32–37. Meliboeus subulatus (Morawitz, 1861), mature larva. 32 Epistome with labrum, dorsal view; 33 Labrum, dorsal view; 34 Pronotal plate of prothorax; 35 Prosternal plate of prothorax; 36 Labio-maxillary complex, external surface; 37 Prementum, external surface (arrow shows posterior border of microsetal area with deep median notch).