Dependency chains

Willow catkins have started to appear on a few trees, so the dependent species will be stirring from their winter hiding places: the larvae of some micromoths live inside the catkins, causing them to drop early; larger moths of the Xanthia family feed on the pollen; and the solitary bee Andrena clarkella gathers the pollen to feed her larvae in the underground burrow. 

Catkins of Salix

As soon as the leaves appear, a completely new set of micromoths and beetles will appear to eat the leaves or make mines inside them. This pattern of a series of dependent species will repeat itself when other trees such as Birch, Oak, Beech and Alder produce their flowers and leaves, but the Willow is the first of our trees to produce these food sources, so it's always the one to kick things off for the new season.

Willow catkins

I don't usually try to identify Willows to a single species because they hybridise and back cross very freely. This one seems most like Goat (Pussy) Willow, but I suspect there's a bit of Grey in there, too. ( I know of a lovely specimen of Dwarf x Eared Willow growing in the middle of an abandoned path: the tree produces catkins, so it's mature, but it is no more than 10 cm. tall. I'll show some pictures in June, when it's in flower.)

From one Willow

Trees support a great deal of our wildlife, and many of them have species of beetle, fly, wasp, moth, butterfly, sawfly or mite that are uniquely dependent on them.

This is the Willow Tar Spot fungus - Rhytisma salicinum which is present on virtually every Willow specimen on the patch.


With so many species fighting for a bit of leaf, it's no surprise that conflict sometimes takes place: the following leaf has been attacked by no fewer than three organisms.

Firstly, there is a gall to the left (the pale green pea-like object). This is caused by a Pontania sp. wasp that affects the growth pattern of the leaf to make a hard structure that it can live - and feed - inside.

Next, we can see the brown marks which are the feeding signs of the larva of the Willow Leaf Beetle - Plagiodera versicolora. Again, virtually every Willow specimen shows signs of feeding, which is carried out by both larvae and adult beetles.

Finally, the entire leaf has been rolled into a tube by the larva of a Tortrix micromoth which, again, lives and feeds inside the tube.


This shows a more conventional roll in the leaf:



Now, does this look like the work of a leaf-miner? I think it does.


But the culprit is the larva of the Willow Leaf Beetle mentioned above.


The larvae crawl over the leaf surface, scraping away the green layers and leaving just a transparent layer that turns brown shortly afterwards. This is really just an external mine, but the larvae are far too large to fit inside the leaf. Large leaf miners come from large leaves, or very thick ones: most leaf-mining species are tiny.