Lasius come home
Alan Roscoe Writtle College, School of Sustainable Environments, Lordship Road,
Writtle, Chelmsford CM1 3RR. Email alan.roscoe@writtle.ac.uk
Further to Tim Gardiner's piece in the May 2009 Newsletter (no.59) concerning Yellow
Meadow Ant Lasius flavus in his garden, I was inspired to check ant activity in my
own garden in Broomfield, north of Chelmsford (TL 704 100).
A large ants' nest had been present for at least three years abutting an east-facing
gravel board on the western edge of the garden and, on checking towards the end of
May, it was established this nest held a colony of L. flavus. The visible portion of the
nest (Plate 4) is some 50 cm long, 20 cm high and 20cm deep. The lawn (80m2)was
completely rotavated and relaid in 1992. Although receiving an initial fertiliser
treatment, it has not been treated since that time in order to mitigate adverse effects on
invertebrates. The area abutting the board has not been strimmed for the past two
years. Apart from grasses, the border also holds Wild Strawberry Fragaria vesca.
Subsequent mowing at the end of May unearthed, as it were, a further three L. flavus
nests at five, six and nine yards from the original and further smaller hills were found
subsequently.
Although we are aware that L. flavus can be a feature of gardens, many books refer to
the species' strong relationship with ancient grasslands or pasture. For example, Gibbons
(1995) refers to large nests up to 50cm high only occurring in 'undisturbed pasture'.
The potentially relatively high density of nests is also seen as typical of the species
with Brian (1977, cited in Skinner and Allen, 1996) noting an area of lowland heath
with an estimated nest density of 0.15 m2. Waloff and Blackith (1962, cited in Curry,
1994) cite an even higher observed density of 0.6 m2 on a neutral grassland site in
England.
The interesting point here is whether anthills of large size and/or high density can
always be taken as indicators of 'ancient grassland' status. Rackham (1986) remarks
that anthills are 'characteristic of grasslands of respectable age' although, in the absence
of categoric evidence, he wisely refrains from defining 'respectable'! And any number
of local nature reserves will claim 'ancient' status for their grasslands on the basis of
presence of large and frequent anthills. Left unmown however, it seems likely that the
anthills in our garden would increase both in number and height and whilst current
density (at least 0.05 m2) is some way below those mentioned above, in time it seems
veiy likely the figure would be far higher.
Whilst the general lack of disturbance at older grassland sites will encourage L. flavus
therefore, the speed of colonisation observed in our suburban garden might indicate
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Essex Field Club Newsletter No. 60, September 2009