03/09/14 - Shield Of Envy

Shield Bugs are attractive insects with their bright colouring, and are easily characterised by their flattened oval-shaped shell, with a triangular plate which sits between the wing cases, this is called the scutellum, meaning ‘small-shield’, which gives Shield Bugs their name. They are also known as Stink Bugs due to their ability to produce a foul smelling liquid from special glands near their legs, when threatened. The majority of species (46 in total) feed on plant sap, however some are predatory, such as the Bronze and Red-legged Shield Bugs which feed on caterpillars and other insects.

The predatory Red-legged Shield Bug - T.Ellers - 26/08

Recently we mentioned about the number that we had come across one morning on Skipwith Common NNR, with five different species found. Starting along the boardwalk adjacent to the bomb bay loop, here we found a number of Bronze Shield Bug (Troilus luridus) and Birch Shield Bug (Elasomostethus interstinctus) – all present on either willow or birch trees. Amongst them were also several nymphs of each species. When hatched Shield Bugs pass through several moults (five in total), changing colour and shape and resembling more like the adults at each stage until they reach the final breeding stage. When they are in the early stages, known as ‘instars’ identifying them can test even the most knowledgeable observer!

The nymph of a Bronze Shield Bug - Skipwith Common - 18/08

Several weeks prior to this visit we’d come across the nymph of a Bronze Shield Bug in the same place, which was a good find with it being a new species for the valley. So it was pleasing to return this time and find some of the adults, which are a rather striking species and stand out from some of the other Shield Bugs due to their metallic colouring. They also have a single yellow marking on either antennae, another good I.D feature to look for. Bronze Shield Bugs are likely to be found on deciduous trees, and are a carnivorous species which feed on small insects. New adults emerge from August onwards, before over-wintering and emerging in late spring to mate.

 Bronze Shield Bug adult - Skipwith Common - 18/08

 Bronze Shield Bug nymph - Skipwith Common - 18/08 

Birch Shield Bugs were far more numerous than Bronze, with at least 25 counted on this visit. As their name suggests they were primarily found on Silver Birch, but we also came across a number of individuals on Salix (willow species). Several nymphs were also found, with these being quite distinctive with their bright green and red markings. The adult bares resemblance to the Hawthorn Shield Bug, but is smaller and lacks the broad brown/reddish markings and has more of a bluey/green colouring. This species is likely to be found throughout woodlands, parks and gardens, the adults over-winter, before re-emerging in spring to lay their eggs, the new group of adults then start to appear from August onwards. Over the last few weeks there definitely seems to have been a sudden emergence on the Common.

 Birch Shield Bug adult - Skipwith Common - 18/08

 Birch Shield Bug nymph - Skipwith Common - 18/08

 

Birch Shield Bug adult - Skipwith Common - 18/08 

Nearby we searched the area of Gorse where we then came across Red-legged (or Forest) Shield Bug (Pentatoma rufipes) and Gorse Shield Bug (Piezodorus lituratus). Gorse Shield Bugs can be easily distinguished by the blue and yellow edge to the abdomen, and the dark purple/red colouring and bright red antennae. This species is likely to be found on heathlands, scrublands and commons, primarily where its food plants Broom and Gorse grow, the latter being where the majority of them were found, including many nymphs, pictured below. Earlier in the year during the spring this species is bright green with blue-edged wing cases, from August young adults then emerge with their purple/red markings, which darken prior to hibernation. We’ve seen a huge emergence over the last few weeks with high counts recorded, found singly on the Gorse (and also nearby Silver Birch), but also many were found in ‘clumps’ on top of each other.

 Gorse Shield Bug adult - Skipwith Common - 18/08

 Gorse Shield Bug adult - Skipwith Common - 18/08

 Gorse Shield Bug nymph - Skipwith Common - 18/08

Adults piled high - Skipwith Common - 18/08

The Red-legged Shield Bug was definitely one of the most striking species seen on this visit, and with its bright colours it stood out a mile amongst the Gorse, carefully balancing on the end of a spike with its long legs. Red-legs are a predatory species, which feed on caterpillars and other insects, as well as fruits. The adults can be seen occasionally in early spring, however usually from July until late autumn. This species over-winters as young larvae which are likely to be found mainly on deciduous trees such as Oak, Silver Birch, Alder and Hazel. This species has two colour forms, one with bright red-legs and antennae, the other has a much darker brown abdomen with a patterned yellow edge, and the pale spot on the back can vary between orange and cream. We were fortunate enough to come cross both colour variations on this visit, pictured below.

 Red-legged Shield Bug - Skipwith Common - 18/08

 Red-legged Shield Bug - Skipwith Common - 18/08

 Red-legged Shield Bug - Skipwith Common - 18/08

 Pair of Red-legged Shield Bugs - Skipwith Common - 18/08

To finish off, on the walk back to the van along the ditch side amongst the Juncus we found a single Hawthorn Shield Bug (Acanthosoma haemorrhoidale), unfortunately it flew off promptly so no photo! The Hawthorn Shield Bug is a bright apple green colour, with broad dark brown/red markings on the abdomen, the abdomen is also tipped red which helps to separate it from the similar Birch Shield Bug. The name suggests that this species will be found on Hawthorn, however we are yet to find it on Hawthorn, species such as Hazel, Holly, Oak and Dogwood are other hot-spots. They over-winter underneath bark, leaf litter etc and emerge in early spring, by late summer the new brood of adults emerge.

It was pleasing to find five species on the Common, and in good numbers, particularly Gorse Shield Bugs. Earlier that week we had also found Hairy (or Sloe) Shield Bug (Dolycoris baccarum) at Thornton Ellers and Green Shield Bug (Palomena prasina) nymphs, no adults as of yet, but with the number of nymphs recorded there should soon be a great deal of adults to look for. Hairy Shield Bugs are not as common as the others mentioned here, so to find two at Thornton Ellers this year has been a good result, and another new species for the valley. As their name suggests this species can be easily distinguished by the long hairs which stand out. They also have rather striking antennae with black and white markings, which also match the edges of the abdomen. Found both times on Bramble which is one of their favoured shrubs, however the larvae particularly favour Blackthorn and those in the Rosacea family. This species over-winters as an adult, emerging in the spring, the new generation of adults can often be found from August onwards.

 Hiding...

 & again....

 

Finally in the open - Hairy Shield Bug adult - T.Ellers - 26/08 

A number of Green Shield Bug nymphs were found in the same area at Thornton Ellers, with at least seven just along one hedgerow, usually on the nettle leaves. Green Shield Bugs are a bright green colour in summer, before turning to brown throughout the winter prior to hibernation. Another sap feeder they are likely to be found in parks and gardens on a variety of deciduous trees, but Hazel is a typically favoured species. Females appear in May, after hibernating in grass tussocks and leaf litter, by June they will have found a male to mate with. Females lay ‘batches’ of eggs, with around 28 in each, with a number of batches laid each female can lay up to 100 eggs, these go on to become the new generation of adults which we are likely to see from September onwards.

 Green Shield Bug nymph, 3rd instar - T.Ellers - 26/08

 Green Shield Bug nymph, 4th instar - T.Ellers - 26/08

 Green Shield Bug nymph, 5th instar - T.Ellers - 26/08

Over the last few weeks the Common has really been producing the goods with many other invertebrates found whilst looking for Shield Bugs - more on this another day!