Hi All,

One interesting growth stage of larvae is the 5th instar and outside academic circles, it's not talked about much.  When we look at capped brood the automatic assumption, for most, is that under the cap is pupa but the exception can be larvae in the 5th instar. According to Rembold et al. 1980, it's the longest period of all instars and has both an open, or pre-capped period, that can last between 24-36 hours and a capped period that can last between 36 and 54 hours. 

As Randy mentioned he harvested in the capped period to check for pollen grains which I believe is the most accurate way but I think it would also be OK to harvest pre-capped 5th instar as long as you ID the larvae correctly. My thinking is that if larvae are feed pollen and digest it enzymatically they should be capable of doing so early and pollen should be present long before the 5th instar but in lesser amounts. 

In the Haydak review, he mentions sources that have observed a change in the color of brood food as nurse bees add pollen when larvae are about 3.5 days old. I've never seen that, and if I did I would think it was contaminated with a bacterial infection like EFB. If Haydak et al. are correct it seems easy enough to harvest some brood food with a grafting tool and make up a slide to verify that turnover period.  I'll do that next - it's a pleasure to use my microscope for something other than nosema. 


Bill Hesbach
Cheshire CT

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