It is a working theory and I saw that someone mentioned coyotes so I wonder if the prosecutor is establishing the foundation for an alternate explanation.
From reading the threads here it seems that the weather in the area was unnussual and not very conducive to fly's developing.
Apparently the last bug guy was asked how he knew the fly's were even developing and i believe the answer was "because they were there".
I am willing to bet that the rebuttal for the late development of the fly's will be that the fly's were suppresed in that area because the the unnussual weather and that they didn't arrive at the body until they were carried there by animals.
The evidence of the animals was established or will be resestablished by calling back the witness who was on the scene.
The presence of a coyote will establish that the range is 10-12 miles and that it probably takes coyote's up to a certain number of days to survey their territory. So, the jury will be given a way to accept that the bug guy testimony is true as to the number of days the bugs were present but not as to the start date.