|March 2006. In response to a request from Dena Smith, curator and assistant professor at the University of Colorado in Boulder, members were asked for their opinions on the possible perpetrator of leaf damage on fossil Cardiospermum leaves (attached). This is not directly a pest problem, but there is interested in possible host-herbivore interpretations. Of the two fossil images, "One is about 45 million years old and the other is 34 million years old (the redder image). It seems that some insect must have been specializing on this group for quite some time."
As the Pestnet community observes leaves of all kinds, much more than most people, and overlaps with the world distribution of Cardiospermum (Sapindaceae: C halicacabum is a pantropical weed, and C grandiflorum is a New World native that has become a serious environmental weed on Rarotonga, in eastern Australia and South Africa; elsewhere?), perhaps someone has seen something like this. The leaves have small ellipses that have very dark "reaction tissue" along the rims. The ellipses never cross over veins. They are not typical of insect damage, but it can't be discounted. The question asked was has anyone seen modern leaf damage like this, on Cardiospermum or other plants? If so, is it insect-associated or from other causation?
It looks like caterpillar damage - too tidy for a beetle or a snail. Perhaps it is some sort of leafroller (Lepidoptera : Tortricidae) caterpillar that damaged the leaf when it was still immature, and the holes have grown as the leaf expanded. There was also a suggestion that Ithe first (redder) image has some characteristic weevil feeding damage. The snout of weevils is capable of causing ‘tidy’ damage on leaves.