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: 

• Linear mine or Ophionome.
• Blotch mine or Stigmatome that can be divided into Othogeneous and Ophiogeneous.
• Serpentine mine or Heliconome.
• Intestinally-coiled mine or Visceronome.
• Digitate or star mines or Asteronome.
• Ptychonome.

The larvae of the S. anomalella produce Ophionomes on the leaf of the roses. I collected several samples of leaves with complete traces of their uninvited occupants, and I use a computer scanner to digitalize them. In Figure 1, some examples of the mines produced by the insect are shown.

Figure 2: other examples of Ophionomes in Rosa leaves created by the larvae of S. anomalella

In Figure 2, another set of leaves are shown on both the upper and lower part. It seems that the larvae excavate only the upper part of the leaf. A microscope section should reveal more details.

Figure 2: other examples of Ophionomes in Rosa leaves mines by the larvae of S. anomalella. 

Using the following script in Python, I have saved each leaf image of Figure 1 and 2 into separate files for the analysis of the meanders.

TO BE CONTINUED (AFTER THE NEXT INFESTATION OF OUR ROSES  …)

REFERENCES

1. Very informative website on Nepticuloidea (See also the link section).
2. A website dedicated to British leaf miners.
3. J. F. Genise. Ichnoentomology: Insect Traces in Soils and Paleosols (Topics in Geobiology). Springer Publisher(2016 ).
4. E.M. Hering. Biology of the Leaf Miners. Springer Publisher (1955).