Anthonomus (s. str.) conspersus Desbrochers des Loges, 1868

Zabulev, Ilya A., 2021, Contribution to the knowledge of the immature stages of Palaearctic species of the genus Anthonomus Germar (Coleoptera: Curculionidae), Zootaxa 5032 (4), pp. 451-488 : 467-472

Anthonomus (s. str.) conspersus Desbrochers des Loges, 1868

Figs. 51–66 , 102 .

Material examined. 12 larvae (30.05– 6.06.2020) and 3 pupae (17.06.2020), Russia, Moscow region, Ramenskiy distr., near of platform Khripan’ (55.654055°N 38.176444°E), ex flower buds of Sorbus aucuparia L., leg. and det. I.A. Zabaluev ( IZCS) .

Description of mature larva. Figs. 51–61 .

Measurements (in mm). Body length: 2.62–3.16 (mean 2.89). Body width: 1.00–1.33 (mean 1.17). Head width: 0.56–0.60 (mean 0.58).

Body whitish or pinkish and in live mature larvae with yellowish spots, distinctly C-shaped curved ( Fig. 51 ). Pronotum with a poorly visible yellowish shield. Spiracles ( Fig. 52 ) bicameral, air tubes with five or six annuli, one pair located on the prothorax and eight pairs located laterally on the abdominal segments I–VIII (Ab1–8). All setae of thoracic and abdominal segments hairlike, from very long to minute, yellowish. Prothorax (Th1) ( Fig. 53 ) with ten prns of unequal length (prns 1 —short, prns 6 —very short, others—from long to very long), two very long ps equal length and two eus (very short and minute). There are two distinct sensilla—one located near the base of prns 1, other—medially. Meso- (Th2) and metathorax (Th3) ( Fig. 53 ) with three prs (one short and two minute), four pds different in length (pds 1, pds 3, and pds 4 —long; pds 2 —short), one short as, three ss (one long, one short and one minute), one long eps, one long ps and two eus (very short and minute). Pedal lobe with five pda different in length: pda 1— very long, pda 2— short, pda 3— minute, pda 4— long, pda 5— minute and located close to the anterior edge of the segment; and with two sensilla located between pda 1 and pda 3. Abdominal segments I–VIII (Ab1–8) ( Fig. 54 ) with two prs (short and minute), five pds different in length (pds 1, pds 3, and pds 5 —long; pds 2 and pds 4 —short), three ss (one long, one short and one minute), two eps (long and short) one very short ps, one very short lsts and three minute eus. Abdominal segment IX (Ab9) ( Fig. 55 ) with six setae dorsally (ds), two ps, and one very short sts. Abdominal segment X (Ab10) without setae.

Head capsule ( Figs. 51 , 56 ) pale yellow, moderately strongly sclerotized (especially along the anterior margin), suboval. Endocarinal line reaching behind middle of the frons and about 2/3 as long as frons. Frontal sutures distinct, extending to antennae. One stemma (st) present close to antenna. Dorsal setae (four des): des 1 short, des 2 medium, des 3 and des 5 long, des 4 absent; des 1 and des 2 located near to middle part of epicranium, des 3 close to frontal suture, des 5 —anterolaterally. There is dorsal sensillum between des 3 and des 5. Frontal area with four fs: fs 1 and fs 3 minute and inconspicuous, fs 2 absent, fs 4 very long, located anterolaterally, fs 5 long, located laterally, close to the border of frons, and with two sensilla—one is between fs 1 and fs 3, closer to the median line, the other is between fs 3 and fs 4. Lateral setae: les 1 short, les 2 about 1/4 as long as les 1 and as long as des 5. Ventral setae: two short vcs. Posterior epicranial area with four minute pes: pes 1, pes 3, and pes 4 arranged in an oblique row, pes 2 —at the side edge, and with two sensilla—one is between pes 3 and endocarinal line, and the other dorsal from des 1. Antenna ( Figs. 57 , 102 ) is one-segmented, consisting of a basal membranous segment bearing an elongate-conical porous sensorium (se) and four sensilla: one ampullacea (sa), two styloconium (ss) and one basiconicum (sb).

Clypeus and mouthparts. Clypeus ( Fig. 58 ) trapezium - shaped, with slightly sinuated anterior margin and with two very short cls placed close to anterior margin of frons and clypeal sensillum (clss) located between them. Labrum ( Fig. 58 ) with three lrs: lrs 1 slightly shorter than lrs 2, lrs 2 long, lrs 3 short, about 1/3 as long as lrs 2. Epipharynx ( Fig. 59 ) with two ams (ams 1 about 1/2 as long and noticeably thinner than ams 2), three als and two short triangular mes. Labral rods (lr) moderately long, converging slightly posteriorly. One sensillum located on both sides of lr and four combined in a single median cluster (esc). Mandibles ( Fig. 60 ) stout, triangular, with two apical teeth; with two rather thick mds equal length, and one mandibular sensillum. Maxilla ( Fig. 61 ) with one very long stps, two long pfs, very short mbs and two sensilla. Mala on the dorsal side with a row of six arrow-shaped dms, on the ventral side with four vms (two comparatively long and two comparatively short) and one sensillum. Maxillary palpi consists of two palpomere: basal palpomere transverse, wider than distal, with one very short mxps and two sensilla, distal—narrow-conical, with one sensillum and a few sensilla at the apex. Prelabium cup-like with four sensilla and one medium prms; ligula with three ligs. Labial palpi elongated, one-segmented, with one sensillum medially and a few sensilla at the apex. Postlabium with three pms: pms 1 short, about 1/3 as long as pms 2, pms 2 —very long, pms 3 —short, slightly shorter than pms 1.

Description of pupa. Figs. 62–64 .

Measurements (in mm). Body length: 2.20–2.70 (mean 2.45). Body width: 1.46–1.57 (mean 1.50). Head width: 0.49–0.52 (mean 0.51).

Coloration. Yellowish white.

Body. Rostrum relatively short, 3x as long as wide; male and female rostrum of the same length. Pronotum transverse, 1.3x as wide as long. Prothoracic depressions lacking. Spiracles well developed on Ab1–5, and vestigial on Ab6.

Chaetotaxy. Setae yellowish, slightly curved, from long to minute. Head capsule with one vs and one os; vs almost straight, 1/2 as long as the width of the rostrum at the base, os slightly longer than vs. Rostrum with one long rs placed posterior to its middle, about 1/2 as long as the rostrum width at the same place, and with one very short (about 1/3 as long as rs) and fine pas, placed at the base of the rostrum. Pronotum (Th1) with one as, two ds, two sls, and three pls; as 1 thin, medium length (noticeably longer than tubercle height), located subapically on anterior surface of the tubercle of medium size; ds 1 minute, located subapically on anterior surface of the very large sharply pointed tubercle, which larger than those elsewhere on pronotum; ds 2 minute, located subapically on anterior surface of the large prominent spiniform tubercle; sls 1–2 and pls 2–3 thin, long, approximately equal length, located near bases of small pointed tubercles, pls 1 short, located near the base of a small triangular tubercle. Femora without fes. Meso- (Th2) and metanotum (Th3) with three long dorsal setae (d) placed medially, they attached on posterior surface of large pointed tubercles on the mesothorax and on low rounded tubercles on the metathorax; the size of the tubercles and the length of the setae gradually decrease towards the middle line. Abdominal tergites (Ab1–8) with three distinct dorsal setae (d), d 1 noticeably thinner and shorter than others, d 2 and d 3 approximately equal length, d 1 on Ab8 located at the bases of low rounded tubercules, d 2 on Ab7–8 located at the base of small convex tubercles, d 3 on Ab7–8 located at the bases of large sharply pointed tubercles. There are minute and inconspicuous setae between d 1 and d 2 and between d 2 and d 3. Lt 1 minute, located at the bases of small tubercles (rounded on Ab1–5 and pointed on Ab6–8); lt 2 long, located at the bases of tubercles (rounded on Ab1–5 and spiniform Ab6–8); l s absent. The size of all tubercles gradually increases towards the apex of the abdomen. Ab9 with one very fine and short ventral setae (v). Urogomphi paired, highly sclerotized, short, contiguous at the bases, noticeably curved, diverge to the sides at the apex.

Biological observations. The biology of this species in Central Europe was studied by Dieckmann (1968). The species inhabits a variety of deciduous and mixed forests, preferring more humid areas ( Fig. 65 ). The host plant is Sorbus , usually S. aucuparia ( Fig. 66 ). In the Moscow region, the first active beetles were recorded in early April (9.04.2020) on trunks of S. aucuparia . The mass appearance of beetles occurs in the second week of May (12.05.2020) and coincides with the beginning of budding in S. aucuparia . Beetles concentrate on inflorescences and actively copulate. On May 26, only single beetles could be found on Sorbus trees, and by the end of May, they had ceased to occur at all. In mid-May, 1 st instar larvae are predominantly found, in late May-early June, mature larvae, and in mid-June, pupae. Moreover, only one larva always lives in one flower bud. The buds torn off from the peduncles containing a mature larva or pupa are capable of making small jumps, this phenomenon has already been noted earlier by Dieckmann (1968) and is also known in A. pedicularius ( Machatschke 1953) . The hatching of beetles of a new generation startsfrom the third week until the end of June and coincides with the stage of ripening of fruits on S. aucuparia . In Petri dishes, young beetles of the new generation actively fed on the green fruits of S. aucuparia , and also ate leaves and petioles. Parasitoids were not observed, but, the larvae of A. conspersus were slightly harmed by the caterpillars of the butterfly Acrobasis advenella (Zincken, 1818) ( Lepidoptera , Pyralidae ), which feed on rowan inflorescences, braiding them with webs. I recorded several cases when a butterfly’s larva ate up a flower bud, in which there was a 2 nd instar larva of a weevil, which, because of this, could not complete metamorphosis and died. However, if the larva was already mature, and the damage to the bud was insignificant, then the larva patched any damage with chewed plant debris and excrement, after which it successfully pupated.

Figures

FIGURES 51–55. Anthonomus conspersus, mature larva. 51—habitus of the body and frontal view of the head, 52—thoracic spiracle, 53—lateral view of thoracic segments, 54—lateral view of abdominal segment I, 55—lateral view of abdominal segments VIII–X (setae: as—alar, ds—dorsal, eps—epipleural, eus—eusternal, lsts—laterosternal, pda—pedal, pds—postdorsal, prns—pronotal, prs—prodorsal, ps—pleural, ss—spiracular, sts—sternal).

FIGURES 56–61. Anthonomus conspersus, mature larva head and mouthparts. 56—head, frontal view, 57—antenna, 58— clypeus and labrum, 59—epipharynx, 60—left mandible, 61—maxillolabial complex, ventral aspect (apical part of the right maxilla is shown in dorsal aspect) (at—antenna, clss—clypeal sensilla, lr—labral rods, st—stemma; setae: als—anterolateral, ams—anteromedial, cls—clypeal, des—dorsal epicranial, dms—dorsal malar, fs—frontal, ligs—ligular, lrs—labral, ls—lateral epicranial, mbs—basiventral malar, mds—mandibular, mes—median, mxps—maxillary palp, pes—postepicranial, pfs—palpiferal, pms—postlabial, prms—prelabial, stps—stipal, vms—ventral malar).

FIGURES 62–64. Anthonomus conspersus, pupa habitus and chaetotaxy. 62—ventral view, 63—dorsal view, 64—lateral view (Th1–3—number of thoracic segments, Ab1–9—number of abdominal segments, sp—spiracle; setae: as—apical, d—dorsal, ds—discal, lt—laterotergal, os—orbital, pas—postantennal, pls—posterolateral, rs—rostral, sls—superlateral, v—ventral, vs— vertical).

FIGURES 65–66. Anthonomus conspersus, biotope and host plant. 65—biotope (Moscow region, Khripan’), 66—inflorescence of Sorbus aucuparia and larva of A. conspersus inside the flower bud.

FIGURES 98–106. Antennae and maxillary palpi of Anthonomus (SEM images). 98—A. pinivorax, 99—antenna of A. rubripes, 100—maxillary palp of A. rubripes, 101—A. incurvus, 102—A. conspersus, 103—A. latior, 104—A. pedicularius, 105—A. pomorum, 106—A. rubi (se—sensorium, sa—sensilla ampullacea, sd—sensilla digitiform, ss—sensilla styloconium, sb—sensilla basiconicum). Scale bars 10 μm.