(388 SNaur) Sminthurinus aureus (Lubbock, 1862)

*albus (Schäffer, 1900)
*anglicanus (Salmon, 1955)
*quadrilineatus (Tullberg, 1871) [in part]

Sminthurinus species are very variable in colour pattern and it is essential to examine the presence or absence of ventral subapical setae on the dens in order to make a correct identification.  A useful (and much easier) character is to examine whether the 'small abdomen' (the animal's "tail end") is visibly sub-segmented or not.  The Sminthurinus aureus group has this body portion wholly fused, while other UK Sminthurinus have a visible division between segments 5 and 6.

The Sminthurinus 'aureus' -group' includes species of Sminthurinus without ventral subapical setae on the dens and an undivided small abdomen. According to Bretfeld (1999), specimens without clear patterning on the abdomen should be recorded under the name Sminthurinus aureus, with different names for different colour patterns on the abdomen. However, it is possible that all these 'species' are simply colour varieties of one taxon that should be called Sminthurinus aureus. The AIDGAP key by Steve Hopkin identifies Sminthurinus elegans (four longitudinal bands), Sminthurinus signatus (two longitudinal bands) and Sminthurinus bimaculatus (pronounced white spot on either side of the abdomen).  Since then we have added Sminthurinus reticulatus, which has cross-banding on its abdomen (apparently widespread south of Birmingham), forma dorsalis ( found by Paul Ardron in Sheffied - see Sminthurinus elegans for pictures), and forma ochropus (Fig. 6 below, taken by Ed Phillips in Moreton Morrell, Worcs).

Sminthurinus aureus as keyed out in the AIDGAP key is very common and widespread, found in leaf litter and low vegetation in almost all terrestrial habitats. It reaches 1.0 mm in length and is diffusely black, brown or yellowish in colour with no clear banding. The fourth antennal segment (ant4) is NOT subdivided (Fig. 1). The outer margin of the mucro is smooth and the inner margin is serrated. The female sub-anal appendages (SAA) are feathery at the tip (Fig. 2) and the long setae surrounding the anus are expanded at the base. Ventral sub apical setae are NOT present on the dens (Fig. 3, 4). The empodium of the third leg (leg3) is slightly shorter than the claw (Fig. 5), but is slightly longer than the claw on leg1 and leg2.

This entire group need a DNA-based taxonomic revision.  During collections for 454 sequencing by Brent Emerson, Peter Shaw collected 2 colour morphs (1 black, 1 yellow) of 'Sminthurinus aureus' from Bookham common, Surrey during 2011.  Their cytochrome oxidase sequences were quite different, supporting colour-pattern species.  However, without more data on intra-population variability this observation is thought-provoking but of little value.

 

 

 

Map of Sminthurinus aureus s. lat., updated January 2013.

 

 

Fig. 1: Antenna of Sminthurinus aureus collected from Earleswood, Warwickshire in August 1962 by Peter Lawrence.

 

 

Fig. 2: Female sub-anal Appendage of the same specimen of Sminthurinus aureus shown in Fig. 1.

 

 

Fig. 3 and 4 : Furca at two levels of focus of Sminthurinus aureus collected from Castle Cary, Somerset in May 1955 by T. Clay.

 

 

 

 

Fig. 5: Foot of the third leg of the same specimen of Sminthurinus aureus shown in Fig. 1.


 

Sminthurinus aureus forma ochropus, photo by Ed Philips from a churchyard, Moreton Morrell, Warwickshire 18 Dec 2012. ID by Frans Janssens.

 
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