12 September 2012

Sheila The Shield Bug Survives!

Shieldbug nymph

I'm pleased to report that contrary to my previous fatalistic prediction for Sheila The Shield Bug Nymph she has actually survived the summer. Of course, this could be one of her siblings, but let's remain hopeful.

As Shield Bugs grow they don't go through a larval stage but gradually morph into their adult shape. Each step in the process is called an instar.

When we first met our Sheila she was in her first instar:

Earlier in the year I saw adult Shield Bugs trundling along the branches of one of the Alemanchiers. Sheila was found on a mint leaf under this tree, so I am guessing the tree rather than the mint is her natural habitat, and that she had fallen down from it. Another piece of evidence in this hypothesis is that she is a Hawthorn Shield Bug. There is a young hawthorn a couple of metres away which has indeed been munched to oblivion, which makes me think trees or at least shrubs are her normal playground.

However, precisely two months later here she is as a teenager (or 'young adult' as my 17 year old son insists) in her fifth and final instar running gaily through the geraniums under the same Alemanchier.

5th instar shield bug

I have a soft spot for Shield Bugs because they remind me of rhinoceroses or triceratopses, so I'm glad to see her survive, but this warm feeling may change when I found out what she is actually eating in my garden.

Here is a fantastic illustration of the various instars Hawthorn SBs go through.

The source for this is British Bugs, but the illustrator is Ashley Wood who has many other bug drawings on her Flickr site which is well worth a look.