Wednesday, 16 July 2014

A Wasp!

The title sounds exciting doesn't it? Hopefully this post will be mildly interesting and informative (I certainly learned a lot whilst writing it!), since it is dedicated to the amazing Ammophila Wasps. I first encountered this fascinating group of wasps last year on some nearby sandy heathland, this group's preferred habitat in the UK (the word Ammophila being a greek translation of 'sand lover'). Of the 200 species in the world, only two occur in the UK, A.sabulosa and A.pubescens and these are more or less restricted to the heaths of southern England.

Today whilst searching for a reported Red-Backed Shrike (which before you ask, no I didn't see it!), I encountered an Ammophila wasp once again. I believe this individual is the scarcer of the two species (A.pubescens) but I am happy to be corrected on this.

I found it excitedly jumping around the sandy path on which we were stood, however before I could grab a photo it disappeared into the heather! A few seconds later, it emerged with a Beautiful Yellow Underwing caterpillar (again please correct me if this identification is incorrect). This is where the lifecycle of these species becomes really quite astonishing!

Before I found this individual, it will have dug a number of small burrows in the sand which acts as a nest for its larvae. Caterpillars are caught, paralysed (but not killed - in order to preserve) and dragged into this burrow. The wasp lays an egg on the initial caterpillar, providing a plentiful food source for the developing wasp larvae. The wasp then continues to monitor the development of this larvae, and provides it with additional food sources when necessary!

As we watched the caterpillar being dragged nearly 10m across the sand and heather, it was clear the wasp new the exact location of its burrow relative to its current position. It seems a number of experiments have been done to analyse exactly how this is achieved; this is copied directly from the BWARS website:

"Baerends used ingenious experiments to show that females use landmarks to learn the location of each nest. Artificial trees were placed near the nesting area and left until the wasps had learned to use them as landmarks. When a tree was experimentally moved, say 5 m to the west, then the wasp searched for its nest 5 m west of its real position. It thus appeared to locate its nest from the nest's position relative to the landmark. These experiments, together with others using artificial nests, partly explained how a female could achieve the incredible feat of caring for two or three nests simultaneously, each at a different stage of development and therefore requiring different amounts of food."

I eventually followed this individual back to its burrow, and filmed the caterpillar's final glimpses of daylight! Apologies for the slightly shaky footage  (and awful video compression) but trying to film a wasp handheld is not the easiest!