It is late August now, soon to be September. Since the third week in August we are seeing large numbers of newly emerged Painted Lady butterflies. How can we distinguish these from their immigrant parents? New emergents are far more vibrant in colour as well as lacking wear and tear. A feature of some fresh Painted Ladies is that the orange band on the upper-side of the forewing has a pinkish flush, a subtle but striking hue.
Here we have them, looking delightful and energetic, darting around flower patches at high speed, easily disturbed by an approach from a human observer and by each other. This behaviour is common in many newly emerged butterflies. These often look unsettled and no clear or obvious intention is apparent in many individuals. It is as if they are unfamiliar with everything, new to the world and unsure about how to behave.
Although it is difficult to say how every individual butterfly will behave, most Painted Lady butterflies will settle down to feed in a concentrated manner. They become less easily agitated and easier to approach. Then there will be time to get close views and good photographs to record your memories of this remarkable summer for this butterfly and the message it is giving us about our world. This switch in behaviour enables the butterflies to build up vital fat reserves for their next big step, their great reverse migration south. In 2009 in the area where I watch butterflies most often, the vast majority of the butterflies departed early in the second week in September. The chances are that you will wake up one day to find they have gone.
This year, this appears the most likely outcome. I have not seen any evidence of breeding among the new butterflies which indicates these are preparing to depart. While these are still present, go out in your garden, parks and anywhere there are flowers to see them. They are seemingly everywhere now and might be more numerous than the numbers that reached our shores this summer. In 2009 there were millions more reverse migrants than immigrants and this may be happening in 2019.
The Painted Ladies flying now look well developed. Many large specimens are present, evidence of high-quality larval foodplants. We had good temperatures and good moisture levels, especially during August. The Painted Lady butterflies flying around my garden at the moment took around 50 days (July 2nd to August 21st, seven weeks) to develop from egg to adult. It is not easy to say whether we have two native generations of the Painted Lady up to this point in the year but we definitely have one home-grown generation. Depending on the weather over the coming weeks, we may get a second generation arising from the immigrants that reached Ireland in late July and early August. This will give us another Painted Lady peak in late September. Until then, we will have to see if there is another chapter left in this remarkable story.