(350POlon) Pogonognathellus longicornis (Muller 1776)

* Architomocerura listeriana (Bagnall, 1940) *plumbeus (Linnaeus, 1758) of Lubbock (1862) [not Lubbock (1873)]


Pogonognathellus (formerly Tomocerus)  longicornis is a common and widespread species, which may be recognised by eye (and often on photographs) by the unique way that the antennae roll into coils, especially when the animal is blown on (Figs. 1 and 2).  It is commonly seen in gardens, and is one of the Collembola regularly found to climb tree trunks, sometimes forming an important member of the canopy community.  It is also the largest UK springtail, reaching 6 mm in length (not including the antennae), with the entertaining claim that (having changed its genus from Tomocerus) it has not just the longest body but the longest name too!

Given a large Tomocerus-like springtail, the easiest confirmation of this species is to check the empodium of the foot which is about 1.2 times as long as the claw due a thin filament coming off its tip (Fig. 5) - our true Tomocerus lack this filament. The spines on the inner side of the dens are simple and there is a pair of large leaf-shaped scales present close to the point where the dentes join the manubrium (Fig. 3). The mucro is long and distinctive (Fig. 4). 

 

2). The empodial appendage of the foot is about 0.7 times as long as the claw. 

Steve Hopkin called this species Tomocerus flavescens, and I take some sympathy with his preference for this generic name, since it is certainly easier to spell!  The distinction between Tomocerus and Pogonognathellus is however clear in several easily seen ways.  In life Pogonognathellus can bend/curl their antennae, while Tomocerus cannot. This is due to their antenna 3, which differ between the genera.  Pogonognathellus antenna 3 tapers gradually, and under high power one can see minute scales on each annulation along this elongated segment; by contrast Tomocerus antenna 3 is a scale-free cylinder of constant diameter.  Pogonognathellus flavescens can only get its antenna 3  into a bend, while Pogonognathellus longicornis alone can produce a true spiral.  Also Pogonognathellus have a large leaf shaped scale each side of the inside of the dentes (lacking in Tomocerus), though these can be knocked off in handling.  

 

Distinguishing between  Pogonognathellus flavescens and Pogonognathellus longicornis is straightforward: P. flavescens has no filament on any empodium, and the antennae are shorter than the body. By contrast longicornis has a clear filament on each empodium and antennae longer than the body.  When seen side by side flavescens tends to have a more yellow ground colour (as its name implies) but this is not dependable

 

Map of Pogonognathellus longicornis; last updated October 2014.

Fig. 1: Pogonognathellus longicornis of 6 mm in length photographed in a garden in Reading.

Fig. 2: Pogonognathellus longicornis of 6 mm in length photographed in a garden in Reading.

Fig. 3: Basal region of the dentes of Pogonognathellus longicornis collected from the New Forest in 1956 by H.E. Goto.

Fig. 4: Mucro of Pogonognathellus longicornis collected from Padstow, Cornwall in March 1951 by T. Clay.

Fig. 5: Foot of the first leg of the same specimen of Pogonognathellus longicornis shown in Fig. 4, showing the empodial filament extending beyond the end of the claw.

 
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