Leptotrachelus dorsalis (Fabricius, 1801)

Erwin, Terry L. & White, William H., 2012, The Nearctic-Caribbean species Leptotrachelus dorsalis (Fabricius, 1801): Larval descriptions with a diagnosis of immature Ctenodactylini and natural history notes on the genus and tribe (Coleoptera, Carabidae), ZooKeys 194, pp. 17-32 : 20-25

Leptotrachelus dorsalis (Fabricius, 1801)

Description of first and third instars.

Coloration (as in Fig. 3 ). Mostly pale cream color with infuscated head capsule, mandibles, and urogomphi, the latter with pale spots; other mouthparts, antennae, and pronotum slightly darker than rest of body.

Microsculpture.

Head capsule without visible sculpticels.

Form.

Head ( Figs 3 , 4 , 8 ). Nasale moderately produced, quarto-dentate, teeth coequal in length; mandibles robust and with obvious serrations medially on blade and posterior to retinaculum; genae not prominent, very slightly wider than distance across stemmata, slightly narrowed to broad neck. Eyes of 6 barely prominent stemmata. Antennomere slightly shorter than porrect mandible; antennomere 2 slightly shorter than 1, 3, and 4. Mandible with prominent retinaculum, curved dentiform; terebral blade obviously serrate, pensillus absent. Ligula of labium slightly produced, unisetose, labrum ventrally sextasetose. Ratios of palpomere lengths can be deduced from the illustrations.

Thorax.

( Figs 3 , 5 , 9 ). Prothorax narrowly quadrate (L1), more broadly quadrate (L3); meso- and metathorax transverse trapezoid, narrow anteriad, broader posteriorly.

Abdomen.

( Figs 3 , 6 , 7 , 10 , 11 ). Segments hexagonal, broad. Urogomphi about one and a half times as long as prothorax is long.

Legs.

( Figs 3 , 12 ). Tarsus unispinose at apex and with a single seta at midpoint dorsally.

Chaetotaxy (L1).

Head. Frontale ( Fig. 4 ) with 7 setae (FR1 - FR7) on each side; and 2 pores (FRc &FRe) on each side; egg burster a lyre-shaped row of short setae. Parietale ( Figs 4A, 4B ) with 19 setae (PA1 - PA19) and 5 pores (PAc, PAj, PAk, PAm, PAn) on each side. Antenna ( Fig. 4A ): antennomere 1 with 3 pores (unlabeled); antennomeres 2 - 4 with no pores; antennomere 3 with 3 setae (AN1 - AN3) and 1 small sensilla near base of sensorial appendage ( Fig. 4A ); antennomere 4 with 4 setae (AN1 - AN4) and 2 small apical sensillae ( Fig. 4A ). Mandible ( Fig. 4A ) with 1 seta (MN1) and 2 pores (MNb - MNc). Labium ( Fig. 4B ): prementum with 3 setae (LA2, LA3, LA7) and 1 pore (LAa) on each side; palpomere 1 with 1 pore (LAb); palpomere 2 and 3 without visible features. Maxilla ( Fig. 4B ): cardo without setae; stipes with 3 constant setae (MX2, MX3, MX4); 5 pores (MXa - MXc), others not labeled; lacinia and galeomeres without setae and pores; maxillary palpomeres without visible sensatory features.

Thorax.

Prothorax: Notum ( Fig. 5A ) with 10 major setae (PR2 - 4, 6, 8 - 13), PR1, 5, 7 absent, and 3 pores (PRc only named one) on each side; pleurite ( Fig. 5B ) with 3 setae (PL9, 10,11), and no pores on each side; episternum ( Fig. 5B ) with 3 setae (unnumbered).

Mesothorax: Notum ( Fig. 5A ) with 14 setae (ME1 - ME14), 3 small auxiliary setae, and 1 pores (MEg) on each side; episternum ( Fig. 5B ) with no setae and no pores; epimeron ( Fig. 5B ) with 1 seta (EM1); pleurite ( Fig. 5B ) with 3 posterior seta (PL1, 5, 6); sternum ( Fig. 5B ) with 1 seta (not numbered) and no pores on each side.

Abdomen.

Tergite I ( Fig. 7A ) with 10 setae (TE1 - TE10, TE8 missing and several accessory setae present) and 1 pore on each side. Tergites II - VIII as in Tergite 1 but with less accessory setae. Tergite IX and urogomphi ( Fig. 7A ) with 8 setae (UR1 - UR8, UR1 missing) and no pores. Epipleurite ( Fig. 7B ) with 2 setae (unnumbered) and no pores. Hypopleurite ( Fig. 7B ) with 7 setae (unnumbered) and no pores. Sterna 1 - 9 ( Fig. 7B ) with 5 or 6 setae each side (unnumbered) all in the same pattern. Sternum IX with 4 setae (ST2 - ST5) on each side.

Legs.

Coxa ( Fig. 12 ) with 1 setae (CO10). Trochanter ( Fig. 12 ) with 8 setae (TR1 - TR8), 2 unnumbered accessory setae and no pores. Femur ( Fig. 12 ) with 6 setae (FE1 - FE6), 1unnumbered accessory seta and no pores. Tibia ( Fig. 12 ) with 6 setae (TI1 - TI7, TI6 missing) and no pores. Tarsus ( Fig. 12 ) 2 segmented, with 6 seta (T21 - T26) and 1 unnumbered accessory seta and no pores on T2, and 1 constant seta on T1 and 1 unnumbered accessory seta and no pores. Claws ( Fig. 12 ) with 1 seta near base.

Description of pupa.

See Fig. 13 . Typical of known carabid pupae, not many of which have been illustrated and described. Note the exceedingly setiferous ocular area of head and cerci.

Characteristics of Ctenodactylini larvae.

Erwin and Medina (2003) showed that van Emden (1948) mixed attributes of two unrelated tribes, Odacanthini ( Colliurini ) and his concept of Ctenodactylini . They found that L3 members of the genus Leptotrachelus contain the following larval attributes found in larvae of Askalaphium depressum : epicranial suture short; cervical groove and keel present; maxilla with inner lobe present; neck not severely constricted; urogomphi nodal, yet not segmented. They located the collection of Leptotrachelus dorsalis larvae that van Emden studied (collected at Oxford, Indiana) in the NMNH, however, they are not in very good condition. They also confirmed his observations and added that second and third instars lack a pencillus and the terebral blade is micro serrate, but refrained from making a more detailed comparison until better specimens were discovered. These observations are now testable with the wealth of material found by the junior author in Houma, Louisiana. Our understanding of the structural attributes of the larval stages for the carabid tribe Ctenodactylini is now progressing.

Erwin and Medina (2003) also studied some poorly preserved specimens of Odacanta melanura L. in the NMNH collection. These specimens differ from ctenodactyline larvae in that the mandible has a single seta pensillus and the maxilla lacks an inner lobe, other features are not discernible. Undescribed larvae of some genera of ctenodactylines were also found in the rotten stems and leaf axils of species of the plant genera Heliconia L. and Calathea G. Mey in low wet places in Amazonian Ecuador and Perú. Adults of Ctenodactyla Dejean occur on species of these plants at night. Further discovery is necessary and subsequent documentation is required to define more accurately the Ctenodactylini , and to explore the patterns that must link these beetles evolutionarily and ecologically to the plants on which they live and the food which they eat.

Figures

Figure 3. Larva, 3 rd instar (top), 2 nd instar (bottom), dorsal aspect, of Leptotrachelus dorsalis (Fabricius). Apparent body length (ABL) (L 3 = 8.9 mm; L 2 = 7.0)

Figure 4. Larval head capsule (L 1) of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Scale line equals 0.5 mm.

Figure 5. Larval thorax (L 1), of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Prothorax T- 1 Mesothorax T- 2 Metathorax T- 3 Episternum ES Epimeron EM. Scale line equals 0.5 mm.

Figure 6. Larval abdomen (L 1), of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Abdominal segments A- 1 through A- 6. Scale line equals 0.5 mm.

Figure 7. Larval abdomen (L 1), of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Abdominal segments A- 7 through A- 10; and cerci and pygidium. Scale line equals 0.5 mm.

Figure 8. Larval head capsule (L 3) of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Scale line equals 0.5 mm.

Figure 9. Larval thorax (L 3), of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Prothorax T- 1 Mesothorax T- 2 Metathorax T- 3. Scale line equals 0.5 mm.

Figure 10. Larval abdomen (L 3), of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Abdominal segments A- 1 through A- 6. Scale line equals 0.5 mm.

Figure 11. Larval abdomen (L 3), of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B ventral aspect. Abdominal segments A- 7 through A- 10 and cerci and pygidium. Scale line equals 0.5 mm.

Figure 12. Coxa CO trochanter TR femur FE and tarsus T 1, T 2, TA of Leptotrachelus dorsalis (Fabricius), posterior lateral aspect. A L 1, top - anterior leg; middle - middle leg; bottom - posterior leg B L 3, top - anterior leg; middle - middle leg; bottom - posterior leg. Scale line equals 0.5 mm.

Figure 13. Pupa of Leptotrachelus dorsalis (Fabricius). A dorsal aspect B left lateral aspect C ventral aspect. Scale line equals 1.0 mm.