Finding eggs of the Black Hairstreak (Satyrium pruni) is a bit more challenging compared to other hairstreaks that overwinter as egg. As the color changes during winter the eggs also get better disguised.
Every species requires its own strategy for tracking down ova. In case of the Black Hairstreak, there are two tips I can provide: First, confirm the location is right. As with every species, searching at the right location is essential. Second, attention to detail. It may require a bit more experience searching for eggs to get results with Black Hairstreaks as eggs really are well hidden in disguise. Personally, I was inspecting the very same growth multiple times before I found eggs on a spot I thought I already checked before.
I got lucky when it comes to location. Just a week ago I met another lepidopterist on a different site. After catching up and having a really interesting talk he revealed me a spot where he knew Black Hairstreaks have a good population. And this tip made my day.
Knowing the right location I was also able to start the search. I knew in advance that this species requires more attention, a better look and serious focus to find eggs. I realized how challenging it was to find eggs after finding the first two (see photo below with three eggs, one of them an empty shell). But I also got an important hint on what to look for. A week later, I found a couple more.
Check the photos below for a view on the habitat. Usually, eggs were laid on the shadow side of growth with a height of 1-2.5 meters. They were found in a height 20cm above ground up to the height of my eyes, about 1.5-2 meters above ground.