With no score and one out in the top of the second, the Giants, who ended up 11-1 winners, had runners on second and third and Freddy Sanchez at the plate when a swarm of bees appeared in right-center field.
Play was halted and as the bees continued to move toward the infield, D-backs players began to leave the field.
The bees congregated at the end of the Giants' first-base dugout, and grounds-crew personnel as well as local fire officials worked at getting rid of them.
"I didn't know what to do," Giants outfielder Angel Pagan said. "If I get stung by one, that means I'm going to get stung by a million. I was right next to the bathroom in case I had to lock myself in.
"I've never seen anything like it before. At first, I was looking around because I saw [D-backs center fielder] Chris Young running toward their bullpen like something happened. All of a sudden, I saw those bees circling around the outfield. Pretty impressive."
Said Young: "I heard it before I saw it."
D-backs Opening Day starter Ian Kennedy was on the mound at the time of the delay. The right-hander went back out during the delay and threw a few more pitches before exiting the field and the team elected not to bring him back after the delay.
"It seems like every day something new happens," Kennedy said. "I've seen it on TV, but never in person. I needed one more pitch to get to 30. I was ready to go back out there, but it was just way too long to get back out there. I didn't know what [Young] was yelling about. He looked like he was running away from the ball that was in right-center and all of a sudden Aaron Hill came up and said there were bees out there. I was not going to get stung so I walked back to the dugout."
Barry Enright took the mound for the D-backs once the game was resumed.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.