Capped and open brood in various stages, from barely hatched to brown-eyed pupa (should not be uncapped!). Day-old eggs (right edge) and a bee emerging (bottom center).
The Dummies book recommends a third inspection to look for congestion and swarm cells 5-6 weeks after hiving your bees. We weren't planning on going into the hive, since we can see all that through the window and everyone looked happy; the Spring Build-Up is on, but they're only up the 14th bar so still have lots of room to work (7 more bars). But then we found a mummified larva and began to suspect a brood disease.
Chalkbrood is a fungal disease that typically happens in the Spring, when a sudden cool and wet spell follows warm weather. Temperatures in the 80s preceded a rainy Memorial Day weekend. Mummies are usually left on the landing board, which is where we found ours, so we think we have a textbook case.
Another key factor is your colony has to be stressed. Could it be that ours feels short on food? We stopped feeding them when the Maples came into bloom. They were followed by Cherries, Mountain Ash and Buckeyes. And the Hawthorns and Lindens are in full stinky bloom now. These are major food sources, but we're thinking we should've kept feeding them. The population has been on the upswing for 4 weeks but our earliest emerging bees only became mature enough to forage about a week ago.
It doesn't make sense to start feeding again at this point but, after finding two more mummies, we decided a mini-inspection was in order.
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Diagnosis: both chilled and chalkbrood. Chilled brood is another springtime disease, similar to chalkbrood but it's not fungal. It happens when the broodnest is bigger than the colony can keep warm when a cold spell hits. The bees cluster for warmth, but they don't cover the entire brood nest, so the larvae on the edges die overnight. These girls seem pretty hygienic and there's daily bee debris, but the Dummies book says it's not a concern unless the count is high (more than 10). We're guessing it means per day, but that's more guidance than any other book provides so I'm even gladder that I kept it.