Cychrus schmidti Chaudoir, 1837

Busato, Enrico, 2012, semigranosus Palliardi, 1825, with a key to the larvae of the European Cychrus species (Coleoptera: Carabidae), Zootaxa 3361, pp. 1-17 : 3-5

Cychrus schmidti Chaudoir, 1837

Silphoid type larva, egg-shaped, broad and depressed; colour brownish black ( Figs. 1, 2). Length from mandible tip to the end of the urogonphi (excluding macrochetae): first instar 6.5–9.5 mm; second instar 9.0–14.0 mm; third instar 13.5–18.0 mm. These measures are only indicative because the total length of the larva can be highly variable, due to its nutritional condition.

Head subquadrate; chaetotaxy of the cephalic region as shown in Fig. 3; FR 2 and FR 4 setae in normal position. Frontal sutures are well visible and sinuous. Metopical suture absent, as always in this genus ( Thompson 1979).

Eye area not very prominent, provided with six stemmata and three setae (PA 7, PA 9, PA 13).

Frontoclypeolabrum markedly longer than wide: l/w ratio: 1.22–1.37. In the lateral view the proximal area shows a marked convexity, which is the thickest point of the frontoclypeolabrum. It gently slopes down towards the distal area forming a fold, approximately perpendicular to the longitudinal axis of the frontoclypeolabrum, in the proximal area of the median lobe and in the points where the lateral lobes fit. In the lateral view the three lobes almost lie on the same level and almost form a single plane, obliquely oriented towards the proximal area of the frontoclypeolabrum. The anterior margin of the frontoclypeolabrum is trilobate ( Fig. 3). The median lobe is flattened and just sketched, almost at the same level of the lateral lobes. The frontoclypeolabrum has five pairs of dorsal setae in the normal position: a long one (FR 7), two medium long ones (FR 5, FR 6), a short one (FR 4) and a very short and thin one (FR 2). In the first instar larvae, in the proximal part of the frontoclypeolabrum on each side, there is the ruptor ovi, formed by a variable number (from two to four) of short pointed spinulae, vertically placed, one anteriorly the other, slightly externally and anteriorly oriented ( Fig. 4). These spinulae are often asymmetrical and can appear in a variable number along the two sides of the same individual.

Antennae ( Figs. 3, 5 – 7) very pubescent, about twice as long as the mandibles (a/M ratio: 2.14–2.19). First segment subcylindrical with three dorsal setae, second similar, about twice as long as the first one and with many setae; third segment again subcylindrical, two thirds as long as the second one and with a diameter slightly shorter than the first two, provided with several setae (longer than the ones on the previous segments) and with a domed sensilla (“accessory item” of the authors: cfr. Casale et al. 1982) lateral to the insertion point of the fourth cylindroconical article. The diameter of the latter is half that of the others and has a group of setae, three of which are clearly longer (AN 4, AN 5, AN 7) and located in the apical part where three small sensilla were also observed. The setae that cover the second, third, and fourth segments, from the base to two thirds along the length, are typical of Cychrus larvae, as far as is known.

Mandibles ( Fig. 8) falciform, narrow and elongate, with the retinacle sharpened and curved, with small pointed teeth in the internal margin, at the base of which there is a tuft of setae (penicillium). The internal margin is smooth; the external margin has a single seta (MN 1) at mid-length.

Maxillae ( Figs. 9, 10) longer than the mandibles, m/M ratio = 1.51–1.53. The stipe is nearly twice as long as wide, slightly dilated apically, and provided with several setae on the internal edge of the dorsal side. On the maxillary palps the first two articles are subquadrate with rounded edges, the third is subcylindrical and clearly more elongated and the fourth is cylindroconic, about twice as long as the second one and a little longer than the third. The first article has medium-length setae on the ventral side ( MX 10) and with one seta of the same length on the dorsal side (indicated by Makarov 1993 but not numbered). Also, the second article has a short seta on the ventral side and another one, almost four times longer, on the dorsal side, both supernumerary. The third article has five-six setae on the dorsal side ( MX 11, MX 12, plus three-four supernumerary ones). The galea has two articles, the first one wider and a little longer than the second and with a seta on the ventral side ( MX 7), and two setae on the dorsal side (not indicated by Bousquet and Goulet 1984, or Makarov 1993). The lacinia is cylindroconical with an apical seta ( MX 6).

Labium ( Figs. 11, 12) with two pairs of ventral setae (LA 1, LA 2), with several dorsal setae (LA 3, LA 4, LA 5, gLA 3). The ligula has a pair of long setae (LA 6). The labial palps are articulated with the sides of the prementum, formed by two subcylindrical articles: the first one is slightly enlarged distally and is half as long as the second, dorsally supplied with three to four setae on the distal third (gLA b); the second one is ovoid, flattened and not truncated apically.

Thorax ( Fig. 13) with a markedly hairy appearance. The external margin of the tergites has four to five long setae. The pronotum, mesonotum and metanotum are subtrapezoidal. The width of the segments increases progressively from pronotum to the metanotum. The pronotum is slightly longer than the other two thoracic segments.

Urotergites ( Fig. 14) clearly covering the pleurae, with large and depressed lateral margins; they enlarge progressively from the first to the fourth, then they narrow significantly from the fifth to the last. Also, these tergites have a significantly hairy appearance, and are laterally provided with four to five long setae each. The setae of the abdominal tergites and the ones of the thoracic tergites give the larva a very hairy look. The setae of the abdominal sclerites are abundant and very long ( Fig. 2).

Sternal area of segments II–VI made up of eight sclerites (two epipleurites and six sternites). The median sternite, which is narrow and long and much larger than the others, is horizontally placed on the inner sternite (originating from the fusion of the inner sternites), almost of the same size. Often in C. schmidti the inner sternites, from abdominal segments I to IV, do not merge together, forming a unique sternite. In segment VII the median and the inner sternites merge together to form a single central sclerite that also includes the outer sternites, showing the median fusion line. In the eighth urite, the hypopleurites are merged with the central sclerite and the total number of abdominal sclerites is reduced to three. In segment IX, all of the abdominal sclerites completely merge. The latero-posterior lobes of urite IX ( Fig. 15) are prominent, sharp-pointed and with a hairy appearance.

Urogomphi conical, narrow and weak, not articulated, slightly divergent, lacking the lateral spine and bearing just two short setae each apically (UR 7, UR 8). Seta UR 5 is absent.

Legs ( Fig. 16) very long; the trochanter, femur, tibia and tarsus have spines in longitudinal rows. The chaetotaxy is in agreement with the model proposed by Makarov (1993) for the genus Carabus Linnaeus, 1758 , but with the addition of a series of four to six supranumerary spines on the ventral side of the tarsus. Moreover, along the dorsal profile of each segment there are many extremely thin setae, forming a tender down.

Table 1 shows the ratios of one left metathoracic leg, as an example, in different instars.