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STUDY BACKGROUND
BIOLOGY AND BEHAVIOR
WHY ON HOUSES?
DAMAGE AND SIDING
INSECTS
CONTROL METHODS
WOODPECKER FAQ

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Which Insects Are They Looking For?   Carpenter Bees | Leafcutter Bees | Grass Bagworms

Carpenter Bees
Carpenter bees are often confused with bumblebees. However, carpenter bees are larger, have bright yellow, orange, or white hairs on their thorax, and have shiny black abdomens (Figure 9). Male carpenter bees do not have stingers, they fly around flowers looking for receptive females. Females do have stingers, but rarely sting. Female carpenter bees drill small perfectly round holes the size of a dime into fence posts, wooden fascia boards, wood overhangs, trees, or other wood structures. She drills straight into the wood about an inch or two, and then turns 90 degrees. This portion of the nest becomes the egg chamber. Single eggs are laid into cells constructed within the egg chamber. A mixture of pollen and nectar is placed alongside the egg, and the cell is sealed with chewed wood pulp. The eggs hatch and the larvae develop into adults, chew through the seal, and emerge in late summer.

Males and females overwinter in abandoned nest tunnels and emerge in April or May. Adult female carpenter bees often return to their place of birth and build their own egg laying chambers extending from previous years' tunnels. A single tunnel one year can become two or three the next. The original entrance hole of the female carpenter bee is usually on the undersides of the wood, there are often large patches of yellowish bee excreta exuding from these holes. Carpenter bee larvae are noisy and tend to attract woodpeckers who will drill holes along the tunnels feeding on the larvae. This activity results in long trenches and holes about 0.5 to 1 inch deep along the wood (Figures 10 and 11).

carpenter bee

Figure 9. Adult Carpenter Bee

fascia boards

Figure 10. Woodpecker damage due to foraging for carpenter bee larva on fascia boards of a house

cedar trim

Figure 11. Woodpecker damage due to foraging for carpenter bee larva on cedar trim boards of a house
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Leafcutter Bees
Leafcutter bees, of the genus Megachilidae, are non-aggressive native bees important as pollinators. They nest in large pithy plants such as roses, in soft rotted wood, and in small crevices and cracks within wood. Leafcutter bees are about the size of a honeybee, but darker with light bands on their abdomens. Solitary bees, individual females dig out nesting areas, create nest cells, and provide young with food. After the nest is made, the females collect fragments of leaves which they cut in a smooth semi-circle about 3⁄4 inch in diameter from the edge of leaves. These pieces are carried back to the nest and used to line the cells. The cell is provisioned with a mixture of nectar and pollen. The egg is laid, and the cell is sealed. The finished nest cell somewhat resembles a cigar butt.

Leafcutter bees will often develop nest sites within specific types of house siding. These nests then attract woodpeckers who will damage the siding in their foraging. Type 111 siding (vertically grooved plywood) has horizontal core gaps exposed when vertical grooves are cut into the plywood. Leafcutter bees will burrow into these gaps to lay their eggs. Woodpeckers will drill horizontal rows of small holes into the siding following these core gaps in an attempt to feed on the larvae. Cedar shakes have many cracks between abutting and overlapping shakes. Leafcutter bees will follow the crack between two adjacent shakes, upward underneath the overlapping upper shakes in order to lay their eggs. Woodpeckers follow these cracks, drilling vertical rows of small holes into the shakes in their foraging attempts.

Grass Bagworms
Psyche casta, known commonly as grass bagworms, are another insect type that woodpeckers look for on houses. The larvae of the Psychidae resemble tiny caterpillars. They construct cases made from fragments of grasses and other plant materials and when the larvae pupate, the case or bag is attached to a tree trunk, a wooden fence, or the siding of a house. Woodpeckers will hammer on a house while searching for the treats hidden inside these inch long bags.


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