|Copyright: Amos Dor (amosdor) (105)|
|Date Taken: 2010-07-19|
|Photo Version: Original Version|
|Date Submitted: 2010-07-19 15:11|
|[Note Guidelines] Photographer's Note|
|In the UK, the Green Shieldbug is unique in having a plain green appearance with no other markings other than the dark straw coloured wing tips terminating the hard wing cases (NB. Newly emerged adults will have clear transparent wing tips). However, in continental Europe there is another similar plain green species, Palomena viridissima. They can be differentiated in the adult stage by P. prasina having a marginally concave forward edge to the pronotum (either side of the head) while P. viridissima has a more rounded convex forward edge. |
Their plain green appearance is remarkably effective camouflage as they roam over a wide range of herbaceous plants - their body segment lines and edges blending very effectively with plant leaf veins.
In the autumn the adult shieldbugs (up to 14mm in length) compensate for the dying back of lush foliage, by changing their green appearance to deep brown allowing them to merge with fallen leaves and dead wood and they will over-winter in this state. But when spring arrives and new plant growth appears, they revert to their summer green colouring. This seasonal colour change is seen in several animal, bird and insect species.
Batches of eggs are laid in early summer (usually on the underside of leaves) when good lush foliage ensures a ready food supply and usually hatch within 7 to 10 days. Tiny little first instar nymphs emerge and usually remain close to their egg cases. Bacteria on the egg cases may be their only food supply for a few days until they undergo their first moult. Each instar moult results in a change of shape, size and colour so it is often difficult to guess what each small insect will turn out to be.
The third image is of a 2nd instar, only 3mm long. At this stage, the nymphs start to disperse and forage independently. The prominent black banding is common to several shieldbug species at this stage.
The 3rd instar (not shown) is larger and the black banding is reduced in area. The 4th instar (not shown) appears like a little flat circular disc and again may not be recognised as a shieldbug. But, in the 5th instar (lower image) it is possible to see the formation of the wing buds developing either side of the 'V' shaped scutellum in the middle of the back.
The development cycle from egg to adult can be completed in about six weeks. And, weather permitting, may allow two generations to mature in a year.
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