How to find Cerceris fumipennis colonies
Locating Colony Habitat
Cerceris fumipennis occurs in suitable habitats from Florida to southern Ontario. Follow these steps:
- Narrow your search area by checking for specimens in your local university or museum collections. If the collection is not well-curated you might have to pick the C. fumipennis out of unidentified material, which is generally easy because the males and females both have distinctive facial and abdominal marks (Fig. 4, 5 and 6). These wasps are commonly collected on flowers some distance from their colonies, so collection records will give you a basic idea of where to start your search.
- Visit the locations on the specimen labels during the wasp’s flight season and look for suitable nest sites. Cerceris fumipennis becomes active around the end of June in Ontario; earlier farther south. The wasps seem to prefer flat open sites exposed to full sunlight for most of the day.
- The ground should be a hard-packed with relatively fine, sandy soil (exclude beaches and sand boxes). Sparse herbaceous vegetation is important so areas with a mixture of about 50% bare hard-packed sand and 50% short herbaceous vegetation are best (Fig. 14). Focus on areas disturbed by humans: baseball diamonds, informal parking spots, infrequently used roads, sandy roadsides, foot paths and soil around fire pits or open campsites (Fig. 15 and 16).
- The buprestids being gathered by C. fumipennis are primarily arboreal and it is unlikely that the wasps would nest far from the “grocery store”. Most known colonies are less than 200 m (200 yards) from a forested area.
- Avoid any freshly dumped mounds of soil or recently landscaped areas. The wasps overwinter approximately 15 cm below the soil surface and seem to build new nest chambers off the hole they emerged from earlier in the summer. For there to be a colony of suitable size the soil below 3 cm must have been left undisturbed for more than a year.
Finding nests at the site
|Figure 4 . Bee Wolf (Philanthus spp).|
|Figure 5 . Tachytes wasp (Tachytes spp).|
After finding a promising colony habitat, you will need to locate the nests:
- Walk around any hard-packed, sparsely vegetated soil and look for nest entrances, which are often tucked beside a tuft of grass. Each digger wasp and bee creates their own telltale entrance. Some wasps cover up the openings but C. fumipennis makes a nice little round mound (approximately 4 cm in diameter) much like an ant mound (Fig. 7). When you find mounds, check to see if they possess a round central entrance hole, which should travel straight down into the nest, not come in from a side location. The diameter of the hole should fit a golf pencil. A number of digger bees make circular mounds but the entrance holes are much smaller.
- Other insects are helpful indicators when trying to locate a C. fumipennis colony; all are taking advantage of similar soil and light conditions. Keep an eye out for digger wasps buzzing over the ground and excavating nests. Bee wolves (Fig. 16), Tachytes wasps (Fig. 17), other Cerceris species (Fig. 18), digger bees (Fig. 19) and tiger beetles (Fig. 20) are found at many C. fumipennis colonies in Ontario.
- Dead buprestids lying around the nests or near the entrances are a good sign that you have found a colony, even if wasps are not active at the site. The female C. fumipennis are encumbered with some of the larger buprestid beetles. If the wasp feels threatened it will drop the large beetle. Without its prey, the urge to “get” a beetle seems to kick in and rather than picking up the dropped beetle, the wasp will head off to catch a new one.
|Figure 6 . Cerceris bicornuta (preys on weevils).||Figure 7 . Digger-bee (clearing burrow entrance).||Figure 8 . Tiger Beetle (Cicindela punctulata).|
Confirming nest occupancy
To determine if the nest holes you have found are occupied by our wasp, try two tricks:
- Look down the burrow hole to see if a female is looking out. Often females wait 2 cm below the nest entrance to guard against other females that may want to take their nest. If the wasp looking back at you is a female C. fumipennis she will have a black head with three creamy yellow square patches in a V shape in the middle of her face (Fig. 5).
- If the hole is empty place a clear plastic cup over the entrance with a stone on top to prevent the cup from blowing away (Fig. 21). Check the cup every five minutes to see if a female is flying around it (Fig. 22) or buzzing inside it. Do not leave the cups unattended for long periods, as wasps may over-heat and die on sunny days. By catching the female you can easily identify the species.
- Use cheap wooden golf tees and coloured collar tabs. Then if the entrance becomes obscured you will know exactly where the nest entrance should be. Writing the nest numbers on the top of the tee or collar will allow you to distinguish each nest.
- Use a GPS to record the geographical co-ordinates.
If the hole is empty place a clear plastic cup over the entrance with a stone on top to prevent the cup from blowing away (Fig. 21). Check the cup every five minutes to see if a female is flying around it (Fig. 22) or buzzing inside it. Do not leave the cups unattended for long periods, as wasps may over-heat and die on sunny days. By catching the female you can easily identify the species.
Finding the first colony will be the hard part but once you have found one colony you will begin to notice them elsewhere. If the wasps are present, you will see them. If they are not conspicuous, then search elsewhere.
Once you have found some colonies you may want to go back and revisit a few of your earlier sites. It is easy to overlook small colonies on days when they are not active such as after a heavy rain. Revisiting possible sites a week later is a good idea.
To optimize efforts you will want to work around the following schedule. In Ontario, the wasps are active from about June 28th to September 5th. There is only a single brood in Ontario but in southern Florida the wasp has two broods with the first one becoming active in early April. Observations in both Ontario and Florida suggest that the wasps rarely forage before 9:30am and most females stop around 6:00pm; females spend the night in their burrows. The wasps are more active on sunny days than cloudy days.
A map of known cerceris colonies. View Cerceris fumipennis Colony Locations & Data in a larger map