Anthonomus (Anthomorphus) pinivorax Silfverberg, 1977

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 : 452-457

Anthonomus (Anthomorphus) pinivorax Silfverberg, 1977

Figs. 1–17 , 98 .

Material examined. 3 larvae and 1 pupa, 15.06.1938, Russia, Leningrad region, Gatchina, ex buds of Picea abies (L.) H. Karst., leg. D.A. Ogloblin, det. I.A. Zabaluev ( ZISP) ; 2 larvae (9.06.2020) and 4 pupae (11– 15.06.2019), Russia, Moscow region, Orekhovo-Zuevsky distr., near Antsiferovo station (55.573371°N 38.757512°E), ex buds of P. abies , leg. and det. I.A. Zabaluev ( IZCS) .

Description of mature larva. Figs. 1–11 .

Measurements (in mm). Body length: 2.82–3.08 (mean 2.95). Body width: 1.26–1.56 (mean 1.41). Head width: 0.67–0.69 (mean 0.68).

Body white or slightly pinkish, C-shaped curved ( Fig. 1 ). Pronotum with a distinct dark brown shield. Spiracles ( Fig. 2 ) bicameral, air tubes with seven to eight annuli on the prothorax and six to seven on the abdomen, 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 long to minute, brownish. Prothorax (Th1) ( Fig. 3 ) with ten prns of unequal length (prns 1 —medium, prns 6 —short, other—from long to very long), two very long ps equal length and two eus (medium and minute). There are two distinct sensilla: one located near the base of prns 1, the other—medially. Meso- (Th2) and metathorax (Th3) ( Fig. 3 ) with three prs (short, and two minute), four pds different in length (pds 1 and pds 3— long; pds 2 and pds 4 —short), one long as, three ss (long, very short and short), one very long eps, one very long ps and two eus (medium and minute). Pedal lobe with five pda different in length: pda 1 and pda 4 long, pda 2 fine and very short, pda 3 and pda 5 minute; pda 5 located close to the anterior edge of the segment; and with two very small and poorly visible sensilla. Abdominal segments I–VIII (Ab1–8) ( Fig. 4 ) 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 (very long, short and minute), two eps (short and long), one very short ps, one very short lsts and three eus (two very short and one minute). Abdominal segment IX (Ab9) ( Fig. 5 ) with six setae dorsally (ds), two ps (long and very short), and one sts. Abdominal segment X (Ab10) without setae.

Head capsule ( Figs. 1 , 6 ) dark brown, cuticle is lighter in the places of attachment of the setae, and epicranial and frontal sutures, strongly sclerotized, almost round. Endocarinal line present, 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 (five des): des 1 and des 2 medium, des 3 and des 5 stout and long, des 4 fine and short; des 1 located near to middle part of epicranium, des 2 —in front of the posterior part of epicranium, des 3 —close to frontal suture, des 4 —laterally of des 3, des 5 —anterolaterally. There is one dorsal sensillum between des 3, des 4 and des 5. Frontal area with four fs: fs 1 and fs 3 minute and inconspicuous, fs 2 absent, fs 4 medium, 2/3 as long as fs 5, fs 5 very 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 4 and fs 5 slightly displaced towards the frontal suture. Lateral setae: les 1 medium, les 2 very long. Ventral setae: two short vcs. Posterior epicranial area with four minute pes and with two sensilla—one is between pes 3 and endocarinal line and the other near des 1. Antenna ( Figs. 7 , 98 ) is one-segmented, consisting of a basal membranous segment bearing a short-conical porous sensorium (se) and five sensilla: one ampullacea (sa), three styloconium (ss) and one basiconicum (sb).

Clypeus and mouthparts. Clypeus ( Fig. 8 ) trapezium - shaped, with two cls placed close to anterior margin of frons and one clypeal sensillum (clss) located between them; cls 2 short, 1/2 as long as cls 1. Labrum ( Fig. 8 ) with three lrs: lrs 1 and lrs 2 long, subequal length, lrs 3 short, 1/2 as long as lrs 1. Epipharynx ( Fig. 9 ) with two fine ams (short and minute), three finger-like als, two short and stout mes. Labral rods (lr) very long, rather narrow, converging distinctly posteriorly. One sensillum located on both sides of lr and four combined in a single median cluster (esc). Mandibles ( Fig. 10 ) slightly elongated, strongly sclerotized, with two apical teeth, mds 1 and mds 2 medium, subequal length, mandibular sensillum located medially. Maxilla ( Fig. 11 ) with one long stps, two long pfs (pfs 1 slightly longer than pfs 2), short mbs and three sensilla. Mala on dorsal side with a row of six finger-like dms, on ventral side with five acuminate vms (three comparatively long and two comparatively short). Maxillary palpi consist of two palpomere; basal palpomere with one short mxps and two sensilla, distal—with one simple sensillum, one digitiform sensillum (sd) laterally, and a few sensilla at the apex. Prelabium cup-like with four sensilla and one medium prms; ligula with three minute ligs. Labial palpi elongated, one-segmented, with one sensillum medially, and a few sensilla at the apex. Postlabium with three pms: pms 1 —medium, 2x as long as pms 3, pms 2 — very long, pms 3 — short.

Description of pupa. Figs. 12–14 .

Measurements (in mm). Body length: 3.38–4.11 (mean 3.73). Body width: 1.38–1.67 (mean 1.49). Head width: 0.56–0.62 (mean 0.58).

Coloration from whitish yellow to yellowish white; over time, the apex of femora and urogomphi gradually darken; in ready to hatch specimens, the pronotum becomes brownish red, while the head and rostrum—black.

Body. Rostrum long, slender, 5.5–6.0x as long as wide. Pronotum transverse, 1.3–1.5x as wide as long. Prothoracic depressions lacking. Spiracles well developed on Ab1–5, and vestigial on Ab6.

Chaetotaxy. Setae on head, pronotum and mesothorax brownish red, stout, almost straight (except os). Setae on metathorax and abdomen brownish, hair - like, from long to minute. Head capsule with one vs and one os; vs almost straight, 2/3 as long as the width of the rostrum at the base, os slightly longer and more curved than vs. Rostrum with one fine rs placed posterior to its middle, about 1/2 as long as the rostrum width at the same place. Pronotum (Th1) with one as, three ds, two sls, and three pls. Ds 1 and ds 3 long, thick, almost straight, in some specimens are located on one convex tubercle, while in others, each seta is located on a separate tubercle; ds 2 slender, 1/2 as long as ds 1, located on a very small, slightly convex tubercle; as of the same length and width as ds 1 and located on apices of small rounded tubercles; sls 1–2 and pls 1–3 thinner and slightly shorter than as, located without obvious tubercles. Femora without setae. Meso- (Th2) and metanotum (Th3) with three long dorsal setae (d) placed medially, setae on mesothorax rather thick, located on apices of small flat tubercles; on metathorax setae thinner and longer, without visible tubercles at the base. Abdominal tergites (Ab1–8) with three distinct dorsal setae (d), d 1 slightly shorter than others, d 2 and d 3 approximately equal length, d 2 on Ab1–2 located at the apex of small flat tubercles, on Ab3–8—at the bases of small pointed tubercles, d 3 on Ab1 located at the base small round tubercles, on Ab2–8—at the bases of spiniform tubercles. There are minute and inconspicuous dorsal setae between d 1 and d 2 and between d 2 and d 3. Lt 1 minute, located at the bases of a small sharply pointed tubercles; lt 2 very long, located at the bases of large spiniform tubercles, which gradually increase towards the apex of the abdomen; l s absent. Abdominal sternites (Ab1–8) and Ab9 without setae. Urogomphi single, strongly sclerotized, straight, at the apex with small hooks directed to the sides.

Biological observations. The biology of this species was studied by Stark (1932) in the Leningrad region and he also very briefly described the immature stages. The larva develops in the terminal buds of young sprouts of Picea abies mainly at a height of 1–1.5 m and by the time of pupation, most of the sprout turns into a dense elongated similarity of the cocoon consisting of plant debris and needles fastened by larval excrement ( Figs. 15–16 ). Heavily infested trees are characterized by yellowed needles. Additional host plants were recorded as Pinus sylvestris L. and P. nigra Arnold ( Dieckmann 1968) ; however, I did not find any infested buds on P. sylvestris growing adjacent to P. abies trees inhabited by A. pinivorax . Many pupae (84%) were infected with a parasitoid Scambus cf. inanis (Schrank, 1802) ( Hymenoptera : Ichneumonidae : Pimplinae) ( Fig. 17 ).

Figures

FIGURES 1–5. Anthonomus pinivorax, mature larva. 1—habitus of the body and frontal view of head, 2—thoracic spiracle, 3—lateral view of thoracic segments, 4—lateral view of abdominal segment I, 5—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 6–11. Anthonomus pinivorax, mature larva head and mouthparts. 6—head, frontal view, 7—antenna, 8—clypeus and labrum, 9—epipharynx, 10—left mandible, 11—maxillolabial complex, ventral aspect (apical part of the right maxilla is shown in dorsal aspect) (at—antenna, clss—clypeal sensilla, esc—epipharyngeal sensilla cluster, 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 12–14. Anthonomus pinivorax, pupa habitus and chaetotaxy. 12—ventral view, 13—dorsal view, 14—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, pls—posterolateral, rs—rostral, sls—superlateral, v—ventral, vs—vertical).

FIGURES 15–17. Anthonomus pinivorax, biotope and host plant. 15—biotope (Moscow region, Antsiferovo), 16—sprout of Picea abies with a bud infected with A. pinivorax, 17—larva of parasitoid ichneumon wasp Scambus cf. inanis on pupa of A. pinivorax.

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.