This past spring and summer I was lucky enough to end up with quite a few passion fruit vines growing on my property. The flowers in the spring were absolutely gorgeous and very exotic looking. The fruit that they produced was sweet and very tasty. But one of the best things about the passion fruit vines was the number and variety of animals it attracted. I’ve already discussed several of those including the zebra long wing butterfly, the brush footed butterfly, and the carpenter ants, but one of the prettiest insects I ever found on the passion fruit vines is the alder leaf beetle. It’s a small (7-8 mm long) deep blue or black shiny beetle with segmented antennas.

I found this little beetle one afternoon in the mid summer when I was on a butterfly hunt. I was looking to get some better photos of the zebra long wings and their caterpillars. The caterpillars tend to live on the undersides of the leaves, so I was looking there when I noticed the little beetle enjoying an afternoon snack. With the regular lens I really couldn’t get a very good picture so I put the macro lens on the camera to take the above photo. It also gave me a good enough view of the little guy to identify him as an alder leaf beetle. I do have alders in my yard, which is the preferred food of the alder leaf beetle, but either this guy was lost or looking for something a little different. I certainly hadn’t expected to find an alder leaf beetle on the passion fruit vine!

Alder leaf beetles are most commonly found on alder trees, but they will also eat the leaves of several other types of trees including beeches and horn woods (and apparently passion fruit vines!). Both the beetles and their black, caterpillar-like larvae feed exclusively on leaves, and can damage the leaves if enough of them are on a tree. The damage is pretty distinctive since alder leaf beetles (and other leaf beetles) chew many, many small holes in the leaves and leave it in a “skeletonized” condition. Fortunately, they are the most ravenous at the end of the summer or early fall just before they go into winter hibernation, and the damaged leaves will soon be shed anyhow. Some scholars even feel that the leaf damage caused by alder leaf beetles is beneficial in thinning the canopy of large, dense trees. Have you had alder leaf beetles or another type of leaf beetle in your garden? Did they do any significant damage?