This morning at approximately 9.30am I noted a large number of bees congregated on the front of the hive many on the ground in front of the hive. At first, I assumed (yes...I know the first three letters having worn an Army uniform) that this was preliminary to a swarm. After a time, I noted a number of dead bees in front of the hive (perhaps 100-200) and looking carefully I thought I could see some bees struggling to pull live bees from the entrance. This is a hive of three deeps with one shallow partially drawn and one shallow with foundation being fed in order to draw comb. Locally (southern Missouri), there is sumac and chicory blooming along with a few other plants. I thought that this could be a pesticide kill but that did not seem likely (although that's a guess on my part) or, more likely, I was seeing robbing behaviour. I sprayed the from of the hive down with water and drastically reduced the entrance. Does this seem like a possible explanation? Is there something else I might be overlooking? Is robbing behaviour common enough that I would see it this way? I had not opened the hive that morning. The bees were being fed with Miller type feeder, nothing exposed. Three days ago when I looked into the hive, the three deeps had 27 frames well covered with bees, some brood and larvae. Any suggestions would appreciated. Thanks, Your Novice Beekeeper, Gerald Herrin