Tag Archives: hymenoptera

Augochlora pura foraging for pollen on maize

Last week I found hundreds of pure green Augochlora (Augochlora pura) foraging for pollen on Zea mays at Stroud Preserve in West Chester, Pennsylvania. Here’s my favorite capture, which shows a bee cutting open an anther with her mandibles.

Augochlora pura foraging for pollen on corn (Zea mays)

I was a tad surprised to see a wind-pollinated plant so mobbed with bees, but a later search of the internet suggested I shouldn’t have been. Even honey bees forage on corn, though the pollen is apparently not as desirable as other sources (e.g., Höcherl et al. 2011). This is also the reason why spraying a cornfield with insecticides can easily cause problems for any bees (and pollen wasps) that collect pollen.

This next photographs shows a better view of the scopa (modified hairs that hold the electrostatically-charged pollen) on the legs and abdomen. It also shows off how incredibly large corn pollen is (perhaps 85 microns, per some estimates, which is huge). Wind-pollinated plants with large pollen are odd.

Augochlora pura scopa with corn pollen

The final photograph shows some pollen grains set in motion by the foraging bee. The odd look (line segments with bright dot in middle) are presumably caused by the flash freezing the fast-moving grains only in the middle of the exposure (1/200 of a second). I’m not exactly sure why the grains are bright. It could be because they are strongly backlit by sun, but it could be something related to how pollen grain exines bend light (they can cause a pollen corona on allergy-alert days). Someday it might be fun to get a rear-curtain flash configured to better capture such motion.

Pure Green Augochlora (Augochlora pura) collecting pollen from corn

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.

Melittobia staking out a mason bee house

I recently set up a mason bee house, and almost instantly attracted a parasitoid, a female Melittobia. She was so tiny that I first thought it was a thrips. But its behavior was odd and definitely not thripsy. The insect would linger near the holes that were being used by mason bees (Chelostoma philadelphi and Osmia sp.), approach, then scurry away, then repeat. On one occasion it peered down an unoccupied hole and paused for several seconds before walking away. It was covered in wood shavings, too, so I inferred that she’d been inside the holes on at least one occasion. All this activity screamed, “parasitoid”, of course, so I had to get some pictures: 

Female Melittobia sp. at a mason bee house.Female Melittobia sp. at a mason bee house.Female Melittobia sp. at a mason bee house. I’m not sure which species she is (there are 14 according to González et al. 2004), but I gather that all members of the genus can parasitize mason bees. Females spend up to 48 hours lurking around a hole (“assessing” per González article) and then puncture a developing larvae with her ovipositor, drink some of the hemolymph, and deposit eggs. There’s a pause in between the hemolymph-feeding and the egg-laying, presumably to allow some of the nutrients to be allocated to eggs. Females are not at all picky about host larvae. Recorded hosts for M. acasta include honeybees, bumblebees, leafcutting bees, and various wasps, flies, beetles, and butterflies (González et al. 2004).

Things get exciting when the wasps eclose, with the early-emerging male killing the slackers that are still developing. There are two types of females: brachytperous (reduced wings) and macroptyrous (regular wing size). I’m assuming the one(s) I viewed are the regular kind.

I’ll post more photographs if I can get them, but whatever is going on inside the holes is of course hidden. But I’m going to make a few glass-sided mason bee houses in the next few weeks so hopefully I can get some larval pics one of these years. This spotting is a reminder to use paper tube inserts whenever possible so that larvae can be examined at the end of the season for parasites. I’m rather interested in parasites but I’d like to encourage a healthy mason bee population when possible.

Much thanks to Ross Hill for identification, and of course to people behind BugGuide for facilitating such IDs. These observations are also logged into iNaturalist.