(086/PCsub) Pseudachorutes subcrassus (Tullberg, 1871)

*tuberculatus Schött, 1902

According to Fjellberg (1998), Pseudachorutes subcrassus reaches 1.8 mm in length. Species of Pseudachorutes with pointed setae on the abdomen and tibiotarsi and post-antennal organ with less than 11 lobes are separated by examining the chaetotaxy. However, the Pseudachorutes parvulus and Pseudachorutes subcrassus of Fjellberg (1998) may not be the same species as specimens labelled with these names in the NHML collection (the main differences are the presence/absence of setae on abd5). The green dots on this map are literature records for Pseudachorutes 'subcrassus'. The red dots represent Pseudachorutes with pointed setae on the abdomen and tibiotarsi and post antennal organ with less than 11 lobes. This Pseudachorutes subcrassus 'group' includes at least two species (but not necessarily the Pseudachorutes subcrassus and Pseudachorutes parvulus of Fjellberg (1998)!). Gama (1964) published an important paper on Pseudachorutes in which differences in chaetotaxy (primarily on abd5) were used to separate the species. However, British specimens are very difficult to assign to Gama's species due to individual variation in the arrangement of setae. The confusion can only be resolved by detailed analysis of fresh material. 

A post-antennal organ is present (Figs. 1 and 2). The furca is well-developed (Fig. 3) and there is no empodium on the foot (Fig. 4).

 

 

 

Map Pseudachorutes subcrassus
Post-antennal organ and ocelli of Pseudachorutes subcrassus

Fig. 1: Post-antennal organ (PAO) and ocelli (A-H) of Pseudachorutes subcrassus collected from Stibbington, Hunts. in November 1961 by J.L. Gilbert.

Post-antennal 0rgan with eight lobes of Pseudachorutes subcrassus

Fig. 2: Post-antennal 0rgan (PAO) with eight lobes of Pseudachorutes subcrassus collected from Kew Gardens in February 1961 by J.L. Gilbert.

Furca of Pseudachorutes subcrassus

Fig. 3: Furca of the same specimen of Pseudachorutes subcrassus shown in Fig. 1. man, manubrium

Third leg of Pseudachorutes subcrassus

Fig. 4: Third leg of the same specimen of Pseudachorutes subcrassus shown in Fig. 2.

 
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