Leaf Mines: Life in (almost) Two Dimensions

The pigmy moths of the family Nepticulidae are the smallest Lepidoptera. They are also called leaf miners as, in the larval stage, they feed on leaves by excavating tunnels in between the two laminas. Some species are considered pests by gardeners and farmers since they feed on fruit plants or flowers, like roses. It is on a plant of rose that grows on a side of our house that I discovered this seasonal intruder that decorate with long tracks lined with the black strip of their frass, the green leaf of our rose. I did some research and I found the name of the culprit: Stigmella anomalella. A nice name for a small pest! Reading more about this little creature, I discovered that has been found fossils dated 97 millions of year ago, this minuscule insect survived dinosaurs (to bother our roses!) so they deserve all my respect for their resilience! – By the way, the study of traces left by insects is a science and it is called Ichnoentomology [3]. Indeed, the curious sinuous trajectory of dwelling inside the leaf cathed my curiosity and I decided to analyze more in details their mining behavior. There are different websites dedicated to the Nepticulidae and on leaf miners in general [2, 3]. I have also found an interesting old book (1955) on the topics of E.M. Hering titled “Biology of the Leaf Miners” that contains interesting information about these insects [4]. Miner tracks are classified  accordingly to their shapes in the following types: 

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