Tag Archives: pollinator

Chinese mantids eat monarch butterflies

This post is a PSA for anyone keen on helping monarchs: if you find Chinese mantids (Tenodera sinensis) in your yard, kill them. Below is a photograph of one that had just snagged a monarch visiting my swamp milkweed. The monarch is fine, by the way. After I intervened she flew off, then came back within seconds and resumed ovipositing.

Monarch butterfly captured by a Chinese mantid (Tenodera sinensi

But unless you’re observing your milkweed patch obsessively, you’ll probably never catch a Chinese mantid in the act. But you can infer their presence by piles of monarch wings (i.e., no body attached). No other animal does this to monarchs.

Monarch butterfly wings left by Chinese mantid predation

And caterpillars are just as susceptible. Here’s a Chinese mantid I interrupted just as it was about to strike:

Colin Purrington Photography: Insects &emdash; Chinese mantis with monarch caterpillar

Chinese mantis can be easily distinguished from any of the native mantids by the presence of a yellow dot in between the forelegs.

Chinese mantis (Tenodera sinensis)

If you find an ootheca (egg case) of this species, crush it. The oothecae have an irregular, messy surface that looks like a blob of brown, poorly-applied insulating foam. Oothecae of the native Carolina mantis are much smoother and streamlined (pic).

First-instar nymph of Chinese mantis (Tenodera sinensis) on ootheca

If you’re like most people (including myself), you grew up believing that mantids are a pesticide-free way of reducing garden pests. How could thousands of web sites be wrong?? The truth is, however, that Chinese mantids are so large that they tend to only eat large insects, and that usually means mainly butterflies, not aphids or other species that are tiny. So if you hate butterflies, by all means encourage Chinese mantids in your yard. But if you like butterflies in your garden, kill the Chinese mantids. And don’t just relocate them, even though that seems like the friendly, eco, green, peace-loving thing to do. Moving introduced, invasive species to another location simply facilitates further spread. It’s like transporting your rabid, aggressive pit bull to a different part of the city (“I didn’t want to euthanize it. Maybe it will thrive in a different neighborhood!”).

FYI, Chinese mantids also eat hummingbirds, plus other birds that are even bigger. The authors of that linked paper conclude,

“Our compilation suggests that praying mantises frequently prey on hummingbirds in gardens in North America; therefore, we suggest caution in use of large-sized mantids, particularly non-native mantids, in gardens for insect pest control.”

Italics mine.

Bee and wasp hotels on iNaturalist

If you’re fond of hole-nesting bees and wasps, please join the new “Bee and Wasp Hotels” project on iNaturalist.org to document the guests and hangerson that arrive at your DIY or purchased hotel. Below are 20 of the most recent observations:

Currently the most photographed visitor is the four-toothed mason wasp (Monobia quadridens). But also plenty of mason bees as well as parasites looking for mason bees. There has also been a slug sighting (don’t ask). 

If this sounds fun but you don’t have a hotel, here are my thoughts on building one.

Mason bee hotel

I built a hotel for mason bees, leafcutter bees, and hole-nesting parasitic wasps and thought I’d post pics in case anybody is looking for tips on how to make one. Overall dimensions are 12x25x11 inches and situated facing southeast so that it catches some good morning sun (the bees like that). I gave it three levels so that I can fuss with one level without disrupting all the tenants, plus the dado joints give the whole structure some stability when fully loaded (it’s, um, a tad heavy). The hotel is elevated to 4 feet on a 4×4 post so that I can easily take photographs of the tenants without stooping.

Mason bee hotel

I also have a piece of galvanized hardware cloth that can be attached (pic below), after all the holes are filled, to keep woodpeckers away. The wire is held by six neodymium magnets glued into small insets on each side. I’ll probably redo it with larger-hole chicken wire, and make it project farther away from the surface. The back of the hotel is a slab of 2×10. To attach the hotel to a post I used a small piece of wood that is first attached to the post, then attached to bottom of the house via four screws (shown below). Everything is just scrap wood from some dismantled cedar planters.

There are hundreds of different bee (Megachilidae) and wasp species that use holes, and all have slightly different preferences for wood type, hole diameter, and depth, so I’ve offered them a variety of accommodations in reeds, logs, and milled lumber, all cut into 7-inch lengths. The reeds are from Phragmites, and each section is cut so that the end has a node, leaving approximately 6 1/2 inches of usable tube. Logs and blocks are drilled with variable sizes of bits, but most are 1/8 inch because at this time of the season there a lot of bees that like that size. Half of the 2x4s have 3-in deep holes and half have 5-in deep holes (I’m interested in whether bees Phragmites culms for mason beeshave a preference). The large log on bottom right also has a mix of 7/16-in and 1/8-in holes, some of which are already filled up (with mixture of nectar, mud, pebbles). Directly above the large log are two smaller ones that show how you can insert 6-in paper tubes into holes. At the end of the season you can easy pull those tubes out and transfer them to a protected location or refrigerator to overwinter. The other advantage of these disposable paper tubes is that you can easily unwind them to collect, study, and clean the pupae. The other paper tube is just a drinking straw I found on Amazon. These tubes will probably not be used this summer but I have them there just in case (the tubes are used by Spring mason bees and my house went up a bit too late this spring to attract any, I think).Drilling holes for mason bee inserts Finally, I have a few large-bore holes up in the attic space just in case that might appeal to a larger bee or wasp, though I probably won’t get a taker.

At the end of the season I’m going to gather up all the wood and reeds and place them in a protected location until next year. I’ll probably end up building a hatching box. After emergence ends I’ll either clean out the wood for reuse or throw it out. You need to do one or the other or risk causing diseases, mites, and parasitoids to build up in your bee house. To give you a visual on one risk, here’s a photo of a mason bee loaded up with phoretic mites. See also the Maclvor and Packer 2015 article, below.

Some design considerations

  1. For larger hole sizes you want at least 6 inches of depth so that bees will oviposit female eggs (i.e., mother controls sex of offspring). Bees will still use shorter holes if that’s all that’s available but it will cause them to oviposit mainly males and males are useless: bad pollinators and they don’t lay eggs. So build your shelves to accommodate 7-in lengths of reeds and logs.
  2. To keep everything dry on something this tall you need a serious roof overhang. Mine extends 5 inches beyond the front of the shelf, plus the wood sections and reeds are set back from that by another inch or so. If you have a shorter house you can have a smaller roof.
  3. Burning the front of the wood allows bees to more easily find their holes, plus causes the wood to heat up faster in the morning sun. Plus torches are fun to use. I got a little carried away and some blocks caught fire.
  4. Don’t use bamboo. Bamboo (and plastic, glass, metal) is too dense and thus doesn’t allow dissipation of moisture from developing larvae. Plus it often cracks as it ages and that allows parasites to enter the brood chamber.
  5. Don’t use treated lumber or fresh cedar. Kills the larvae, apparently.
  6. Pine is fine but I think harder wood is preferable because the drilled holes are smoother.

If you need inspiration there are thousands of mason bee house designs on Pinterest.

Guest list

Here are the tenants so far: an Osmia, several Chelostoma philadelphi, and a creepy wasp that I’d wager is a parasitoid waiting for an egg-laying opportunity.

My goals for building this house are mainly for edutainment (please join my iNaturalist project if you’re interested) but a bonus would be better pollination of my kiwi vine and strawberries. But that’s not a guaranteed because many solitary bees are oligolectic (collect pollen from only certain species of plants), and I’m not sure which species specialize on Actinidia and Frageria. I’m looking forward to next year when I can put out the blocks for (larger) spring mason bees, which I think are good for early strawberry pollination.

Further reading