Stem miner (Diptera: Agromyzidae) in Apocynum

I found a larva mining a stem of the host in mid-July. The mining resulted in a blotchy brownish or reddish discoloration to the surface of the stem. There was no clear pattern to the deposition of frass in the mine.

I was also able to locate the oviposition site in this stem. It consisted of a round oviposition hole in the stem epidermis, the edges of the hole curled upward/outward to form a slight collar around the hole, the collar oriented at a less than 90-degree angle relative to the long axis of the stem, suggesting the egg was inserted obliquely and not straight down. The collar was a brownish color, as was a small oval patch of tissue between the hole and the start of the mine, this patch apparently being the location where the egg was placed under the epidermis. Away from this location led the beginning of the stem mine, linear and slightly raised but not discolored relative to surrounding stem tissue, and approximately twice as wide as the diameter of the oviposition hole.

The larva, nearly mature when I collected the plant material, was visible through the stem epidermis as it fed. The posterior portion of the larva's cephaloskeleton appeared as if divided into 3 parts rather than 2, indicating the larva belonged to the subfamily Agromyzinae. When finished feeding, in captivity, the larva thrust its body partway out of the stem and pupariated in this position, with the anterior half of the puparium protruding from the mine through a hole in the epidermis at a 45-degree angle to the long axis of the stem. The puparium was straw-colored with a pair of black anterior spiracles borne on stalks. I was not able to rear the adult fly.