Starring Chromolaena odorata as the plant
(Chromolaena means colorful cloak. Odorata denotes fragrance.)
Asteraceae (Aster Family)
With Cremastobombycia chromolaenae as the miner
(Cremasto means suspended. Bombycia means reed, or flute made of reeds. Chromolaenae refers to the plant host.)
Gracillaridae (Leaf Miner Moths)
Today’s botanical hotspot was the Jupiter Ridge Natural Area at Jupiter, Florida, a large sunny scrub with a marsh in the middle, plus a tidal creek. Habitat diversity translates into biodiversity, making the site a great place to go. The pretty flowers today were escaped horticultural water lilies in pink and blue, picture perfect and fragrant abuzz with bees, but we’ll feature a more mundane creature. Leafminers were at work, and intriguing if not eye candy. Leafminers are larvae of various insects trapped for a portion of their youth tunneling through leaf tissue, feasting on salad protected from the harsh world. Arthropod boarding school.
The most conspicuous of the miners at this season infests a large native weed coming into its Holiday blossom time, Jack-in-the-Bush. Its miner-miner 49er has two remarkable truths:
- The insect ducked formal “discovery” until 2013. (Nobody cares about a worm in a weed.)
- The larva is not satisfied with a mere tunnel. Instead, it excavates a huge white blotch separating the upper epidermis (skin) from the tissues below. Sometimes the blotch covers the entire leaf surface. A heavy infestation resembles ornamental variegation.
You might wonder how a tiny caterpillar can undermine a big area. It swings its head vigorously from side to side like a reaper with a scythe.
Watch the little swinger here: CLICK
At this juncture the discussion broadens from the single species pair to miners in general, remembering how they represent diverse major insect groups. So what I’m about to say applies to some but probably not all. Leaf miners have a problem…they might outlive their host leaf.
Heaven forbid, what happens if the leaf ages and drops before the little feller completes its tunnel time? That brings us to the botanical anti-aging hormones, cytokinins (SIGH-toh-kine-ins).
I doubt cytokinins are a fountain of youth on human epidermis, but they do work on plants.
If you are a parasite inhabiting a leaf, you wish your blade a long healthy life. Leaf miners do more than just wish, they promote foliar youth and longevity. Although I have trouble finding convincing photogenic examples in South Florida, farther north where leaves seasonally discolor and drop, leaf miners release cytokinins to insure their home, or at least the miner’s mineshaft region. Such green areas housing miners surrounded by deteriorating leaf tissues are called green islands. CLICK to see one. The miner is at the lower right corner of the island.
We must wonder if the miner is merely protecting its lair from routine leaf aging. Alternatively (or additionally), perhaps the life-extending hormone therapy mitigates the miner’s damage.
It gets more complicated. Does the miner make the cytokinins, or does it cause the leaf to? Or maybe neither: There is a third factor in the equation; it seems the miner can’t prescribe the cytokinin rejuvenation without the help of symbiotic bacteria. In short, all three species are involved: bacteria, insect larva, and plant.
For those wishing to burrow deeper: MINE THIS