Even after adding another 600 images and associated text files, detectNet neural network failed to show any real signs of convergence, even after a couple of hours on AWS P100 GPU:

Since I want to make use of the recently released Nvidia Nano dev kit, it that to get this network to converge, more images are needed. This is probably because, as mentioned previously, there are at least 10 species of slug and 1 species of snail being photographed, which means approx. 160 images for each species which is a very small data set for this kind of thing.

If detectNet fails to converge, I'm sure it's possible to run YOLOV3 on the Nano without too much trouble.