Bombus pullatus Nest Photos

We stayed at Pitilla Research Station, a part of Guanacaste National Park in northcentral Costa Rica. This was the starting point of a 1-2 km hike to the nest.

The hike to the nest involved strenuous trudging through mud in our rubber boots through primary forest. Nearer the nest we reached secondary forest, we saw several B. pullatus foraging on this hilltop overlooking Lake Nicaragua and a nearby volcano.

Calixto and Wilberth led us to the nest and stood at a healthy distance while I made my first observations. The habitat near the nest was quite disturbed.

The nest located at the center of the image is difficult to see. Below is a closer view of the exterior of the nest. Note the conical mound of cut vegetation. A black bee is fanning outside the nest entrance near the bottom. In this picture you can also see the bare area in the front of the nest. This bare soil surrounded the nest, suggesting the nest materials were gathered from around the nest. Andy Deans recorded data on entrance usage from afar while I stood near the nest communicating the observations.

Andy's hesitance was for good reason - he got stung a couple of times by a particularly aggressive bee. I had my (hot!) protective gear to protect me most of the time.

At left: Bees fanning at the entrance of the nest. At right: B. pullatus cleaning itself on a leaf near the nest.

To begin to excavate the nest, we cleared away the vegetation around the nest slowly, which did not put us in the bees favor. During this time we continued to collect all foragers and aggressive guards. Then we began to pull apart the nest and grabbed many of the remaining nurse bees from within to make our internal nest observations and final worker counts. Note the thick vegetative exterior on the nest, built around live and dead plant stems.

Photos of the brood inside the nest. Note the pollen pockets which were later formed as pots. These pollen pots are scattered across the nest. Also note the largely exposed older larvae (donut shaped cells with milky white larvae inside), queen (larger) and worker/male (smaller) light colored pupal cells, brood at all stages from egg to pupae, and the cluster of honey pots near the front. The nest was rather large for a bumble bee nest. We then covered the nest with the loose canopy - it was still functioning a month later.