Adomerus biguttatus ( = Sehirus biguttatus), the Cow-wheat Shieldbug re-found in Worcestershire

Harry Green (compiler)

On 30^th March 2011 Nick Button found the shieldbug Sehirus biguttatus by the side of a ride in Worcestershire Wildlife Trust reserve Monkwood, near Sinton Green. The Worcestershire Biological Records Centre database contains two previous records from Monkwood dated August 1968–June 1970. Of these, one grid reference is for the centre of the wood, the other at the north end. The records are by I L Crombie and the time span suggests he found them in the wood on several occasions. Apparently Monkwood has been the only known location in Worcestershire for many years: there are also records from the Shropshire part (north side) of Wyre Forest.

The British bugs website states: A medium-sized shiny black shieldbug which has a pale margin to the pronotum and forewings and two pale spots on the corium. This species can be found under stands of the foodplant, Cow-wheat Melampyrum pratense, growing in sunny woodland clearings and rides. There is one generation per year, the new generation becoming adult in August. Scarce, with a scattered distribution mainly confined to southern England and south Wales. It has declined in recent years due to the widespread neglect of traditional woodland management practices which create suitable cleared areas.

Evans & Edmondson (2005) note that it is a ground living species found in the sunnier parts of woodlands on various soils. In Worcestershire the associated food plant, Cow-wheat, tends to have a more westerly distribution. This being so, and encouraged by Nick’s record, the Wyre Forest Study Group searched hard for the bug and found it on 16^th April 2011 near Uncllys in Wyre Forest. Rosemary Winnall writes as follows:

On a recent field trip, the Wyre Forest Study Group was delighted to find a small insect that some members had been searching for for a while! Paul Allen (ably encouraged by Brett Westwood) eventually spotted the tiny 5.5mm long shieldbug Sehirus (Adomerus) biguttatus on a sunny bank in leaf litter under its food-plant Common Cow-wheat Melampyrum pratense. In previous searches we had been looking on the plants, but Paul instead heaped some leaf litter from below the Cow-wheat into a white tray and searched through carefully. No others were found in spite of checks on the food-plants - perhaps it comes out to feed at night? The shieldbug was fast moving and was not keen to be photographed!

It seems likely that this species will occur at other sites in Worcestershire where there is Cow-wheat. It is however hard to find. The early stages are probably present during June and July. The full-grown insect may be found from August through to the following spring. Since Monkwood became a nature reserve there has been a programme of re-instating coppice regimes and widening the main ride. Both these practices have created open sunny areas favoured by the bug so hopefully the population will grow. Nationally the species appears to be uncommon with widely scattered records shown on the map derived from the NBN website but this may perhaps reflect its elusiveness rather than great rarity.

References

British Bugs website at http://www.britishbugs.org.uk/heteroptera/Cydnidae/adomerus_biguttatus.html or search for www.britishbugs.org.uk and then for Adomerus biguttatus in space provided.

Evans, M. & Edmondson, R. 2005. A photographic guide to the shieldbugs and squashbugs of the British Isles. WGUK.

Images

Fig. 4. Adomerus biguttatus (Sehirus biguttatus), Wyre Forest, April 2011. This picture of the bug on litter gives an idea of size. ©Brett Westwood.