A cradle of roses

As the rose hips ripen here in Maine, they are acquiring both a pretty red blush and quite a few pockmarks.  What has been causing these small scars on the surfaces of the rose hips?

A ripening rose hip with several small, dark wounds.

In the past, I had often seen rose hip flies (Rhagoletis basiola) sitting on and nearby the rose hips.  These flies did not seem to be doing much, though, except sometimes rotating their wings in what may be a mating display.  However, over the last few days, I have caught a couple of the flies in the act --

A rose hip fly (Rhagoletis basiola) ovipositing into a rose hip.

 -- puncturing the rose hips with their ovipositors and laying their eggs inside.

Another rose hip fly (Rhagoletis basiola) ovipositing into a rose hip.

When I waited for one of the flies to finish laying and leave, I saw a fresh hole in the rose hip.  Checking back the next day, I found that the hole had scarred over to match the many other pockmarks on the rose hip.