Rhinusa asellus (Gravenhorst, 1807)
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publication ID |
https://dx.doi.org/10.3897/zookeys.1195.112328 |
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publication LSID |
lsid:zoobank.org:pub:617FBE9C-72D1-479D-8336-1E9325D74B93 |
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persistent identifier |
https://treatment.plazi.org/id/61EA2828-2E91-5D54-B637-040BF6182F5C |
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treatment provided by |
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scientific name |
Rhinusa asellus (Gravenhorst, 1807) |
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1) Rhinusa asellus (Gravenhorst, 1807) View in CoL
Material examined.
16 mature larvae; 4 ♂ pupae and 1 ♀ pupa. Serbia, Pirot, 700 m a.s.l., ex Verbascum thapsus L., 06.03.2017, leg., det. I. Toševski.
Description of mature larva
(Figs 1A, B View Figure 1 , 2A-E View Figure 2 , 3A-C View Figure 3 ). Measurements (in mm). Body length: 5.72-9.00 (avg. 7.55). The widest place in the body (meso- and metathorax) measures up to 2.40. Head width: 0.80-1.00 (avg. 0.85).
General. Body elongate, moderately slender, curved, rounded in cross section (Fig. 1A View Figure 1 ). Prothorax small, pronotal shield not pigmented. Mesothorax slightly smaller than metathorax; each divided dorsally into two folds (prodorsal fold smaller than postdorsal fold). Pedal folds of thoracic segments isolated, conical, prominent. Abdominal segments I-III of similar size, next segments tapering towards posterior body end. Abdominal segments I-VII each divided dorsally into two folds; postdorsal folds distinctly higher than prodorsal. Segments VIII and IX dorsally undivided. Epipleural folds of segments I-VII slightly conical. Laterosternal and eusternal folds of segments I-VII conical, weakly isolated. Abdominal segment X divided into four folds of equal size. Anus situated ventrally.
All spiracles unicameral; thoracic spiracles placed laterally close to mesothorax; abdominal spiracles (Fig. 1A View Figure 1 ) placed mediolaterally on segments I-VIII.
Colouration. Yellow to brownish head, medial parts of epicranium less sclerotised (Fig. 1B View Figure 1 ). All thoracic and abdominal segments white (Fig. 1A View Figure 1 ). Cuticle covered with fine asperities.
Vestiture. Setae on body thin, yellowish, different in length (very short or medium).
Head capsule (Figs 1B View Figure 1 , 2A View Figure 2 ). Head rather wide, endocarinal line present, reaching to 1/2 of the length of frons. Frontal sutures on head wide, unclear. Two pairs of stemmata (st): first in the form of a prominent pigmented spot with a convex cornea, close to the end of the frontal suture, second pair small, placed laterally, above the anterior stemma. Des1 short, located in the central part of epicranium; long des2 placed mediolaterally; long des3 located anteriorly on epicranium close to the border with the frontal suture; des4 short; long des5 located anterolaterally above stemma (Fig. 2A View Figure 2 ). Fs1 absent; fs2 short; fs3 absent; fs4 long, located anteriorly; and long fs5 located anterolaterally, close to antenna (Fig. 2A View Figure 2 ). Les1 and les2 medium, and one short ves. Epicranial area with four pes.
Antennae placed distally of the frontal suture, on the inside; membranous and distinctly convex basal article bearing one conical sensorium, relatively short, plus four sensilla differing in type: two basiconica and two styloconica (Fig. 2B View Figure 2 ).
Clypeus (Fig. 2C View Figure 2 ) ~ 3 × as wide as long with two medium cls, localised posterolaterally, with one sensillum between them; basal part distinctly sclerotised; anterior border straight.
Mouth parts. Labrum (Fig. 2C View Figure 2 ) trapezoidal, ~ 2.2 × as wide as long, with three piliform lrs, different in length; lrs1 elongated, located medially, lrs2 elongated, located posteromedially, and lrs3 short, located anterolaterally; anterior border bi-sinuate. Epipharynx (Fig. 2C View Figure 2 ) with three medium finger-like als, almost identical in length; two medium piliform ams; and single medium finger-like mes; labral rods (lr) distinct, kidney shaped. Mandibles (Fig. 2D View Figure 2 ) bifid, cutting edge with additional protuberance; two medium piliform mds, both located in shallow pits, close to lateral border. Maxillolabial complex: maxilla (Fig. 2E View Figure 2 ) stipes with one stps, two pfs and one very short mbs and one sensillum, stps and both pfs1-2 relatively long; mala with six finger-like dms variable in length; four piliform vms, medium to short in length. Maxillary palpi two-segmented; basal palpomere distinctly wider than distal one; length ratio of basal and distal palpomeres almost 1:1; basal palpomere with short mpxs and one sensillum, distal palpomere with a group of four apical sensilla in terminal receptive area. Prementum (Fig. 2E View Figure 2 ) oval-shaped, with one long prms; ligula with round margin and three short ligs; premental sclerite broad, sclerotised, cup-shaped, posterior extension medium in length, with thick apex. Labial palpi one-segmented; palpi with a single pore, and a group of four apical sensilla (ampullacea) on terminal receptive area; surface of labium smooth. Postmentum (Fig. 2E View Figure 2 ) with three pms, medium pms1 located posterolaterally, elongated pms2 located mediolaterally, and medium pms3 located anterolaterally; posterior part of membranous area covered with knobby asperities.
Thorax. Prothorax (Fig. 3A View Figure 3 ) with nine medium prns, dorsal sclerite weakly visible; two medium ps; and single short eus. Mesothorax (Fig. 3A View Figure 3 ) with one short prs, one short and two medium pds; one medium as; three minute and one medium ss; one medium eps; one medium ps; and single short eus. Chae-totaxy of metathorax (Fig. 3A View Figure 3 ) almost identical to that of mesothorax. Each pedal area of thoracic segments with three long and two short pda.
Abdomen. Segments I-VII (Fig. 3B, C View Figure 3 ) with one very short prs; two short and one medium pds; one minute and one medium ss; one medium eps; one medium ps; one short lsts; and two short eus. Segment VIII (Fig. 3B, C View Figure 3 ) with two medium and one short pds; one medium ss; one medium eps; one medium ps; and two short eus. Abdominal segment IX (Fig. 3C View Figure 3 ) with one minute ps and one minute sts.
Description of pupa
(Figs 4A-C View Figure 4 , 5A-C View Figure 5 ). Measurements (in mm). Body length: 4.50-6.00; body width: 2.75-3.15; thorax width: 1.75-2.90; rostrum length: up to 1.60 ♂ and 2.60 ♀.
Body. Integument brownish; moderately stout, curved. Elongated head protuberances present (h-pr) on head above eyes. Rostrum very elongate, in male almost 4 × as long as wide and reaching metacoxae; in female 7 × as long as wide and protruding past metacoxae. Pronotum trapezoidal, 1.5 × as wide as long. Pronotal protuberances (p-pr) well developed, conical, sclerotised, fused at base. Mesonotum slightly smaller than metanotum. Abdominal segments I-VI almost identical in size; segment VII semicircular; segment VIII narrow; segment IX reduced. Abdominal segment VIII dorsally with rounded, prominent, sclerotised abdominal protuberance (a-pr). Urogomphi (ur) vestigial, in the form of very short sclerotised, sharp protuberances. (Fig. 5C View Figure 5 ).
Chaetotaxy. Well developed, setae medium to elongated, transparent. Head with one very short sos, one medium os, and one medium-sized pas. Rostrum with two rs and one minute es (Fig. 5A View Figure 5 ). Pronotum with two as, one ds, two ls, and four pls almost equal in length; ds located in shallow pits. Dorsal parts of meso- and metathorax with three setae of various lengths, placed medially. Apex of femora with two long fes (Fig. 5A-C View Figure 5 ). Procoxae with a single seta (cs). Abdominal segments I-VII with six setae dorsally, variable in length: first minute, placed anteromedially; second and fourth minute; third and fifth medium, placed close to posterior margin of the segment; six, medium, placed below stigma (on segments VI and VII all setae medium). Abdominal segment VIII with four elongated setae dorsally. Each lateral part of abdominal segments I-VII with a single medium seta. Ventral parts of abdominal segments I-VIII with four setae, median pair longer than other ventral setae. Abdominal segment IX with four medium-sized setae ventrally (Fig. 5A-C View Figure 5 ).
Remarks and comparative notes.
This species is widely distributed in central and southern Europe, in the states of the Caucasus, and in western and central Turkey ( Alonso-Zarazaga et al. 2023). Recently, it was reported as introduced into the USA ( DiGirolomo et al. 2019). It is clearly related to R. tetra , from which the adult differs by the longer rostrum, especially in the female, the elongated shape of the elytra, and the male genitalia ( Caldara 2014).
Biological notes.
Larval hosts of R. asellus are restricted to species of Verbascum ( V. nigrum L., V. phlomoides L., V. pulverulentum Vill., V. sinuatum L., V. thapsoides Schw., V. thapsus , and V. virgatum Stokes; Caldara 2014). The biology of this species was carefully studied by Gumovsky (2007). Adults can be found feeding on the shoots and leaves of the host plant beginning in May. Oviposition sites are typically concentrated in the top portion of the host plant. The female drills a hole in the host-plant tissues with her very long rostrum, and then she lays eggs there. Eggs develop in ~ 7 days. After hatching, the larva bores into the stem and feeds on plant tissues, often leading to swelling of the stem. Mature larvae form a pupal cell just beneath the outer layer of plant tissue within the stem. Larval and pupal development take on average 20 and 10 days, respectively. Sometimes R. asellus lives on the same host plant as R. tetra , although they occupy different niches.
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