We are very thankful to leafminer experts Peter Ridland, Melbourne and Charley Eiseman, MA, USA (http://charleyeiseman.com/) and author of Leafminers of North America, who have done so much to arrive at an identification of the Galapagos leafminer symptom sent by Paul Fontaine, Belgium, neary 50 days ago. Peter also sent a paper which is attached here. grahame
From Peter Ridland to Charley Eiseman
I found only one record of a leafminer on Tournefortia (or Heliotropium) in the Galapagos. Landry (2006) described Dialectica galapagosensis sp. n. and listed a number of specimens, including one recorded from Tournefortia rufo sericeae. There was no indication of the leafmine. This is the only record I have found of a leafminer from Tournefortia.
I see from your book p 1423 First Edition
"Liriomyza blechi Spencer has been reared from Heliotropium sp. (Spencer & Stegmaier 1973)".
Spencer 1990 p. 196 "In Florida a species closely related to, if not identical with, Liriomyza blechi Spencer (in Spencer and Stegmaier, 1973) has been recorded on Heliotropium sp. More material is required before the status of this species can be further clarified."
Do the two images ring any bells for you about type of leafminer that might be involved? Sasakawa (2007) listed 5 agromyzid species from the Galapagos, but none from the Boraginales as far as I can make out.
From Charley Eiseman to Peter Ridland cc Pestnet
Hi Peter and Grahame,
My initial impression from the shape of this mine is Agromyzidae or Gracillariidae (there are also some sawflies on Boraginaceae, but they can safely be ruled out). From what I can see here I would go with Agromyzidae--it appears that the mine begins with a puncture rather than an eggshell on the leaf surface, and a gracillariid mine would be epidermal initially (confined to one leaf surface) whereas this one seems to be full-depth. I also think I am seeing the open anterior end of an empty puparium at the end of the mine (the farthest to the left of the three wide lobes), which would definitely indicate Agromyzidae and would be consistent with Liriomyza blechi. That species has quite variable mines, depending on the host, and was covered in my most recent paper with Owen Lonsdale--here's the link, in case Grahame doesn't have it: https://www.dropbox.com/s/10879rha2kocao8/Eiseman%20et%20al%202021%20Agromyzidae.pdf?dl=0
Of course, I can't be sure of the species without having a reared adult, as I have no idea what leafminers exist in the Galapagos!