By: Frances Owen, JCC Naturalist
Pollinator week may be past (June 21st-June 27th) but we think it’s always a great time to celebrate the pollinators who help our local ecosystems thrive. That’s why we want to share some amazing updates for our Observation Solitary Bee Hotels placed at three Johnson County Conservation properties!
You may already be familiar with solitary bee hotels. They have become popular enough over the last few years that they are available for purchase at most garden centers, and many DIY tutorials exist to help you create your own (visit the blog post here to see how we made our observation hotels!). The past two years, Johnson County Conservation has hosted a Woodworking for Wildlife: Solitary Bee Hotel class, during which participants construct bee hotels that allow you to observe the fascinating lifecycle of these otherwise mostly unnoticed insects (For an excellent in depth look at Iowa’s solitary bees, see our blog post here). We put out four of these observation hotels (marked in the three maps below) in three Johnson County Conservation areas this spring and let nature take its course. You will never guess who moved in.
Bee Hotel #1 at Cangleska Wakan
4045 245th St NE, Solon, IA 52333
We hung all of our bee hotels up in early April in anticipation of all the early mason bees that would be out looking for a place to nest. The bee hotel at Cangleska Wakan is located on the brochure post near the local foods operation, Bountiful Harvest, and right next to the grass parking area. We didn’t see any activity, until June 1st, when suddenly we had an unexpected (and delightful) insect take up residence.
June 1st, we discovered a female mason wasp carefully stuffing caterpillars into a chamber she had already begun sealing with mud! If you watch the video above carefully, you may be able to see her egg dangling from the top of the chamber. The egg shakes when she occasionally bumps into it. Mason wasps (similarly to mason bees) are solitary, and use mud to create chambers for their offspring to develop. Instead of providing pollen (like a mason bee), the female wasp will gather small caterpillars for her young. She stings the caterpillars, paralyzing them so they remain alive but unable to move. Once she has laid an egg in the chamber and sealed the caterpillars inside with a wall of mud, the egg will hatch and the resulting wasp larva will feed on the captive caterpillars. How gnarly is that? Scroll through the photos below to see the nest progress.
First sign of activity June 1st. The female wasp busily packs paralyzed caterpillars into the chamber. 
June 4th, only 3 days later, you can see she has built more nest chambers out of mud and stashed additional caterpillars. 
June 10th, some of the mud walls appear to have crumbled and it looks like she has shoved new green caterpillars into the first chamber. 
June 16, possibly the same wasp has continued nesting in the chamber above. Some of the white larva are visible in the earlier chambers and the amber color is present where the larva has pupated. 
June 16th, a smaller groove in the hotel appears to be occupied now in addition to the 2 larger grooves. 
June 18th, more white wasp larva are visible and more have pupated. Another groove above the first two is being filled with caterpillars.
Bee Hotel #2 at Kent Park Conservation Education Center Trail
2048 HWY 6 NW Oxford, IA 52322
June 11th, we started to notice some activity in the observation hotel located at the beginning of the Conservation Education Center Trail. Someone was carrying grass and katydids into the chambers! After a quick bit of research we discovered this was yet ANOTHER genus of wasp called grass-carrying wasps. Also solitary, a single female uses dried grass to form the chambers in their nest, and stuff them full of paralyzed katydids. Each chamber usually has one egg laid inside. Just like the mason wasp, the egg will hatch and the larva will feed on the katydids. These wasps will sometimes nest in the grooves of window sills as well.
Both mason wasps and grass-carrying wasps are types of solitary wasp. Similar to the lifecycle and temperament of solitary nesting bees, these wasps are not aggressive and can be safely viewed within the solitary bee hotels.
Grass and katydids were first discovered in this box on June 11th. 
Also on June 11th, look closely at the left end of the grass filled chamber to glimpse the dark female wasp. 
June 14th, the grass-carrying wasp has filled three distinct chambers with katydids. 
June 16th, now there are four chambers, and the larva in the first chamber is starting to weave a protective cocoon. 
June 18th, there are now six chambers, the first three chambers have made cocoons. Smaller larva and katydids are visible in the other three chambers. 
June 30th, all of the wasp larva in the upper chambers have made cocoons. The bottom groove now has five chambers filled with larva and what appear to be tiny brown crickets instead of bright green katydids. 
June 30th, bits of grass stick out of the nest box, plugging the groove to protect the developing larva inside.
Bee Hotel #3 at Kent Park Youth Group Camp Trail Head
2048 HWY 6 NW Oxford, IA 52322
June 16th we noticed activity in the bee hotel located at the trail head near the Youth Group Camp (marked by one of the pink stars in the above Kent Park map). This hotel appears to have BOTH mason wasp and grass-carrying wasp activity inside.
Bee Hotel #4 Solon Prairie
713 East 5th Street, Solon, IA 52333
A fourth bee hotel was placed on the back side of the sign at Solon Prairie. This 3 acre prairie is tiny, but filled with a plethora of native prairie species (157 native plant species have been documented on site). We hope it will be a perfect spot to see some additional bee diversity within our bee hotel. As of June 18th, we saw the first signs of leafcutter bees! Tiny pieces of leaves carefully cut and stuffed into two of the nesting chambers. Leaf cutter bees have enlarged mandibles specifically for cutting out small circles from leaves to line their nest chambers. Instead of collecting insects, these solitary bees collect pollen to feed their offspring. Learn more about them in a previous JCC blog post here.
Closing thoughts
Wasps have a bad reputation for being generally aggressive. Fortunately, these solitary wasps are harmless to us, not aggressive, and can offer benefits in addition to those offered by our friendly neighborhood solitary bees. Both mason wasps and grass carrier wasps will visit flowers for nectar as adults, which is what they eat for food. While gathering nectar, they can distribute pollen. Along with their pollination services, their developing offspring eat insects that could cause damage to developing plants (the caterpillars, katydids, and crickets all feed on plants).
We hope you visit one (or all three!) of these parks to see these amazing insects in action. If you have a bee hotel, don’t be surprised if one of these tiny (and helpful!) predators takes up residence.
Johnson County Conservation - Nature Notes 