All members of the genus Arrhopalites have only one ocellus on each side of the head. Arrhopalitescaecus is a common and widespread species that is found both inside and outside caves. The empodium of the foot is slightly shorter than the claw (Fig. 1). The mucro is serrated on both sides (Fig. 2) and there is a strong spine on the ventral side of the dens near the mucro (Fig. 3). The female sub-anal appendage is not expanded at the tip (Fig. 4) and the fourth antennal segment (ant4) is subdivided into five subsegments although the divisions between them are indistinct (Fig. 5).
Fig. 1 (above): Foot of Arrhopalites caecus collected from Jealotts Hill, Berkshire in February 1967 by Harold Gough.
Fig. 2 (above): Oblique view of the distal furca of Arrhopalites caecus collected from Jealotts Hill, Berkshire in 1966 by Harold Gough. Note that the mucro is serrated on both the inner and outer edges.
Fig. 3 (above): Lateral view of the distal furca of Arrhopalites caecus collected from Jealotts Hill, Berkshire in June 1969 by Harold Gough. There is a strong spine on the ventral side of the dens near the mucro.
Fig. 5 (below): Antenna of the same specimen of Arrhopalites caecus shown in Fig. 2. The fourth antennal segment (ant4) is subdivided into five indistinct subsegments.
Fig. 4 (above): Female subanal appendages (SAA) of the same specimen of Arrhopalites caecus shown in Fig. 2.
