I’m mainly writing this post because of one picture I wanted to share, but first I’ll provide a little context. In the moth genus Bucculatrix, most species start out life as leafminers, forming short linear mines. Bucculatrix locuples is typical in this respect, but is the only species known to feed on alders (Betulaceae: Alnus spp.). Here are vacated mines of two larvae (the one on the right is a little harder to discern because of brown splotches caused by an unrelated injury to the leaf):
After making these initial mines, larvae of most Bucculatrix species exit and spend the rest of their lives feeding on the leaf externally. Here again, B. locuples is no different:
And like its relatives, externally feeding larvae of B. locuples periodically spin flat, oval cocoons in which to molt. At first, the molting cocoons of B. locuples are white as in other species…
…but older larvae spin yellow molting cocoons:
Mature larvae of Bucculatrix species spin an elaborate, elongate cocoon in which to pupate; this is typically white and longitudinally ribbed. Before spinning this, some species first erect a ring of white silken pillars around the future cocoon site; the purpose of this fence is apparently to deter marauding ants, though I find it difficult to picture how it could be effective. In B. locuples, both the ribbed cocoon and the silk fence are made of dark brown silk, and I imagine the yellow tint to the final molting cocoon has something to do with the transition in the type of silk the larva is producing. I have always had a hard time photographing these fence-encircled cocoons due to the limited depth of field in macro lenses (and I’m too busy to bother with focus stacking), but the particular individual I was rearing this month spun its cocoon in a corner at the bottom of its vial (rather than on a flat surface as is typical), so that the pillars were bent toward each other and I was able to get a photo that gives a decent look at what’s going on:
So that’s all I wanted to show you. Oh, and today the moth emerged; it’s the first adult of B. locuples I’ve seen.