Teasels

I got around to having a look at some teasels today which are growing near our house in Westcott, Bucks.  I cut off a random sample of 20 seed heads, of which 15 were found to be tenanted with single caterpillars of Endothenia gentianaeana.  I've previously found them elsewhere in the village but these are close enough to add to the garden list!  The larvae were confirmed as gentianaeana by the deep brown head and lack of an anal comb (see UK Moths), but all the same a few have been retained to rear through. 

Endothenia gentianaeana caterpillar in teasel

Endothenia gentianaeana caterpillar

Endothenia gentianaeana caterpillar (lack of anal comb)

This is the most likely species to be found in teasels but the larva does have to be inspected to rule out Endothenia marginana and the two common Blastobasis species (all of which can also be found feeding on the central pith) and Cochylis roseana (which burrows through the seeds).  The best way to open the seed head is to make a short vertical cut with a penknife at the top and then pull the teasel gently apart, otherwise you might end up slicing into the caterpillar.  Its presence will be obvious because most of the central pith will have been eaten and there will be lots of frass, although the beast itself may need coaxing out because when disturbed they often wriggle backwards into the stem as shown in the top photo.  Once inspected, I close the teasel and use an elastic band to keep it together, giving the caterpillar a chance to complete its life cycle.
Dave Wilton