Notes on Theridion hemerobium

From The Newsletter No. 98 November 2003

In 1996 Theridion hemerobium Simon, 1914 was found in a fishing complex at Wanlip, north of Leicester, a first record for the county. Situated on the River Soar flood-plain, the area had been used for gravel extraction. At the time this species was thought to be restricted to a small area of the fishing complex, with its epicentre at a fishing platform and duck nesting-box in a large area of shallow marsh at one end of one of the many fishing lakes. The species was recorded over a number of years, usually from man-made structures except on one occasion when I found it in reedmace standing in 15 cm of water whilst looking for Tetragnatha striata.

Table 1. Records of Theridion hemerobium from Wanlip.
06/09/96..1f....SK605117..in empty plastic barrel at side of fishing lake
01/06/97..2f....SK604115..on duck nesting box in marsh; in reedmace*
24/08/97..1f....SK604115..under fishing platform in marsh
06/06/99..4m5f..SK604116..under fishing platform in marsh
* = more details in text above, m = male...f = female

Theridion hemerobium was forgotten for several years; then I moved house and started to collect in my new locality. About 200 m from my home, the Grand Union Canal runs alongside an area of rough open space with a minor sewage pumping station close to the canal. On 24th July 2003 two female specimens were collected from the steel barred fence surrounding the pumping station. They remained in the boot of my car for the following two weeks; they were then identified as T. hemerobium.

This find suggested that the species might be a lot commoner than previously suspected, so a series of collecting trips were organised aimed at finding this species in as many new 10 x 10 km squares within the county as possible. Ordnance Survey maps were consulted and the Rivers Soar and Trent, and the Grand Union Canal were selected to be visited. It soon became apparent that T. hemerobium was not being found on brick and concrete structures, but was present on wood and metal ones. So looking for this species on the many brick and concrete bridges that cross the Leicestershire waterways proved futile. This species did occur on the wooden railings of one bridge at Thurmaston (18th August 2003). I have no idea why this is the case, but suggest that competition from other Theridion species (T. tinctum, T. mystaceum, T. melanurum and T. varians) for breeding areas and possible threats from other spider species such as Amaurobius may be contributory factors.

This species is probably quite mobile and able to colonise new, relatively temporary structures such as fishing platforms, fences and signs. So far the specimens that have been collected all seem to be found in slightly shaded/sheltered areas and all seem to need to be either hanging/concealed under something (stiles, fishing platforms and signs) or in a small retreat on bare metal surfaces.

A further factor seems to be that in the county T. hemerobium is restricted to the canal and river systems, with the few lakes visited away from these producing no specimens.

In Leicestershire this species has been found on the Nottinghamshire border, in the north, on the River Trent; to the Northamptonshire border in the south, along the Grand Union Canal. At several places this species has only been found as singletons after an hour or so of searching; while at other sites (such as at Foxton 26/08/03) 6 specimens were collected in 15 minutes from a 50 metre stretch of the canal, with only a twentieth of the potential habitat being surveyed.

Table 2. Leicestershire records of Theridion hemerobium.
Leicester: on metal fence 20 m from Grand Union Canal................24/07/2003......2f...........SP574984
Newton Harcourt: on lock gates, fence, and lock sign..................10/08/2003......1m,5f......SP636966
Rothley: under fishing platform over lake on fence 40 m from river..11/08/2003......2f...........SK596128
Sawley Cut: on temporary 'footpath closed' sign at side of canal....13/08/2003......1f...........SK470309
Leicester: under wooden walk-way at side of canal......................15/08/2003......1f...........SK578016
Thurmaston: on wooden bridge over the River Soar.......................18/08/2003......1f ..........SK608094
Foxton:*six on metal pilings at side of canal. 2 on metal sign board .26/08/2003......8f*.........SP699899
Foxton: on metal pilings at side of canal......................................26/08/2003......1m,3f......SP701897
Market Harborough: on metal signpost, 5 m from canal...................26/08/2003......1f ...........SP720901
Loughborough: under top step of a stile, 5 m from the River Soar......27/08/2003......1f.........SK518222

It is obvious from this small survey that this species has been vastly overlooked and is quite likely to be found to be commonplace along most of our canal and river systems throughout southern Britain.
 
Added by John Partridge at 16:38 on Thu 9th Feb 2012. Return to Summary for Theridion hemerobium