Gracilentulus, Tuxen, 1963

Nakamura, Osami, 2021, The Japanese species of the genus Gracilentulus (Protura: Acerentomidae), Zootaxa 4991 (2), pp. 271-294 : 292-293

Key to the species without sensillum b’ on foretarsus of Gracilentulus

A key to Gracilentulus species by Szeptycki (1993) includes all species known to that time, including those of the “ gracilis ” group (foretarsal sensillum b’ present, b longer than half of c) is currently still available. An updated key to species without sensillum b' on the foretarsus is provided.

1. Foretarsal sensillum b subequal to c and d in length.......................................................... 2

- Foretarsal sensillum b longer than c and d.................................................................. 3

2. Foretarsal sensillum f halfway between e and g; abdominal tergites II–VI with eight anterior setae................................................................................................... G. floridanus (Ewing) ( USA)

- Foretarsal sensillum f close to e; abdominal tergites II–VI with six anterior setae.......... G. microtrichus sp. nov. ( Japan)

3. Foretarsal sensillum e longer than f; labial palpus with four setae and one sensillum................................. 4

- Foretarsal sensillum e subequal to or shorter than f; labial palpus with three setae and one sensillum.................... 5

4. Foretarsal sensillum t1 distal to α3; abdominal tergite VII with eight anterior setae............ G. shippingensis Yin ( China)

- Foretarsal sensillum t1 proximal to α3; abdominal tergite VII with six anterior setae..... G. chichibuensis Nakamura ( Japan)

5. Foretarsal sensillum c and d proximal to t2; f subequal to g in length; a not reaching base of t2..... G. aokii Imadaté ( Japan)

- Foretarsal sensillum c and d at same level with t2; f longer than g; a surpassing base of t2........................... 6

6. Foretarsal sensillum a’ surpassing base of α4; P3a absent on abdominal tergite VI; P3 on tergite VI anterior to other posterior setae................................................................ G. maijiawensis Yin & Imadaté ( China)

- Foretarsal sensillum a’ not reaching base of α4; P3a present on abdominal tergite VI; P3 on tergite VI in same row as other posterior setae............................................................... G. macrotarsus sp. nov. ( Japan)