Cleopomiarus longirostris (Gyllenhal, 1838)

Skuhrovec, Jiri, Gosik, Rafal, Caldara, Roberto, Tosevski, Ivo, Letowski, Jacek & Szwaj, Ewelina, 2018, Morphological characters of immature stages of Palaearctic species of Cleopomiarus and Miarus and their systematic value in Mecinini (Coleoptera, Curculionidae, Curculioninae), ZooKeys 808, pp. 23-92 : 36-39

Cleopomiarus longirostris (Gyllenhal, 1838) Figures 21, 22, 23-24, 25-26, 27, 28-30

Material examined.

11 L3 larvae: south-eastern France, Menton, July 2007, ex capsules of Campanula trachelium L., leg. and det. R. Caldara, all determined by association with reared adults.

Description.

Measurements (in mm). Body length: 6.60-8.70 (mean 8.3). Body width (abdominal segments I–III) up to 2.44. Head width: 1.05-1.16 (mean 1.10).

General. Body elongated, slender, curved, rounded in cross section (Fig. 21).

Colouration. Pale brown head with indistinct pattern around frontal sutures (Fig. 21). All thoracic and abdominal segments from distinctly white to slightly yellow (Fig. 21).

Vestiture. Setae on body thin, orange, distinctly different in length (minute to very short or long to very long). Cuticle slightly asperate.

Head capsule (Fig. 22). Head oval, slightly flattened laterally. Frontal sutures medium width, distinct. Two pairs of stemmata (st), anterior one in the form of a large pigmented spot; and posterior one in form of a very small pigmented spot, located on each side close des5. Des1-3 long; des4 short and des5 long to very long (Fig. 22). Fs1 long; fs2 absent; fs3 short; fs4 long; and long fs5 (Fig. 22). Les1 and les2 as long as des5; both ves very short. Epicranial area with three pes and two sensilla in line with des2.

Antennae bearing one medium size conical sensorium, and basal membranous article with four sensilla different in length, three behind conical sensorium, and one ahead of it (Fig. 23).

Clypeus (Fig. 25) approximately 2.5 times as wide as long with two short cls, cls2 distinctly longer than cls1, and one sensillum.

Mouthparts. Labrum (Fig. 25) less than 2.5 times as wide as long, with three piliform lms, different in the length; lms1 located anteromedially, close to margin, lms2 located in the middle, and lms3 located posterolaterally; lms1 and lms2 of medium size, and lms3 distinctly shorter than the previous two; only lms2 distinctly reaches labral margin. Epipharynx (Fig. 26) with three long finger-like als, two als of identical in length, and the third one distinctly shorter and also located more close to labral rods (lr); with three ams in different length, ams1 and ams2 piliform and short, finger-like ams3 and enlarged in middle, and also located more close to lr; without mes; labral rods (lr) distinct, elongated, oval. Mandibles (Fig. 24) bifid; mds1 relatively long, piliform, located basally; mds2 medium size, piliform, located distinctly apically and laterally. Maxilla (Fig. 27) stipes with very long stps and both pfs; very short to minute mbs, and sensillum close to mbs; mala with six medium sized finger-like dms; five vms, different in length, three setae medium size, and two setae very short. Maxillary palpi: basal palpomere with one short mxps and two sensilla; distal palpomere with, cuticular apical processes; length ratio of basal and distal palpomeres 1:0.8. Prelabium (Fig. 27) with one relatively long prms; ligula with two very short to minute ligs; premental sclerite broad, ring-shaped. Labial palpi with two palpomeres; length ratio of basal and distal palpomeres 1:0.8; each of the palpomeres with one sensillum, distal palpomere with short, cuticular apical processes. Postlabium (Fig. 27) with very short pms1 located basally, very long pms2 located medially and short to medium size pms3 located apically; membranous area basolaterally distinctly asperate.

Thorax. Prothorax (Fig. 28) with eight very long to long and one very short to minute prns, small pigmented dorsal sclerite present with four long prns, this sclerite subdivided in two triangular plates medially; two very long to long ps; and one short to very short eus. Meso- and metathorax (Fig. 28) with one long prs, three medium to long pds; one very long to long as; two very long and one very short to minute ss; one long eps; one long ps; and one short to very short eus. Each pedal area of the thoracic segments with 5-6 very long to long pda.

Abdomen. Abdominal segments I–VII (Figs 29-30) with one short prs; one long and two short to very short pds (order: short, long, short); one long and one minute ss; two very long to long eps; one relatively long ps; one short lsts; and two very short eus. Abdominal segment VIII (Fig. 30) with one very short to minute prs; one relatively long and two very short pds (order: very short, long, very short); one relatively long and one minute ss; two relatively long eps; one short ps; one short lsts; and two very short eus. Abdominal segment IX (Fig. 30) with three relatively long and one very short to minute ds; one relatively long and sometimes one minute ps; and two short to very short sts. Abdominal segment X (Fig. 30) with one very short seta (ts).

Biology.

We can confirm that larvae of this species feed on seed capsules of Campanula trachelium L., where they pupate without producing galls. It is noteworthy that adults did not exit by making a hole in the capsules but remained inside with the rostrum folded in the ventral canal until these opened spontaneously and forcefully, blowing up the seeds. On the other hand, it would be impossible, especially for the female, to straighten up the very long rostrum inside the capsule due to the limited available space. This is a more advantageous behaviour and apparently opposite to that of Rhopalapion longirostre (Olivier, 1807), another species where the female rostrum is more than twice as long as the stout male rostrum. In this species, Wilhelm et al. (2011) argued that the long rostrum is presumably an advantage for this weevil because its larvae can feed on plant parts with high energy density into buds (i.e., pollen grains) and that natural selection favours rostrum elongation. However, these authors reported that the elongated rostrum of females also bears a high risk when metamorphosed weevils attempt to leave their site of pupal development, which is the dry seed chambers, and therefore mortality during escaping may counteract selection for rostrum elongation, thus placing a limit on rostrum exaggeration. It is noteworthy that R. longirostre does not possess a ventral canal, which allows it to retain the folded rostrum.

Remarks.

This species is only known from France, Italy, and Switzerland, where it is quite common. The adult is very closely related to C. graminis , as also supported by preliminary molecular studies (I Toševski, unpublished data), from which it differs only by the very long rostrum especially in the female and usually by the larger size ( Caldara and Legalov 2016). Therefore, the larval differences between these two taxa, in C. longirostris antennae bearing one medium size conical sensorium and four sensilla (Fig. 23), dorsal setae (except des4) extremely long (Fig. 22), prothorax with eight very long and one very short to minute prns (Fig. 28), are very important since they allow easy separation of these two species.