As autumn nights begin to turn colder, many butterfly species search for hibernation locations, such as cracks in loose boards, stonewalls and tree bark. Properly constructed, a butterfly gourd house can provide a secure supplemental hibernation location for these butterflies looking for winter shelter from predators and inclement weather. According to the Brookfield Botanical Garden's "The Butterfly Gardener's Guide," a range of butterflies, including members of the large brushfoot butterfly family (such as the Common Yellow Glider and the Wall Butterfly) will use this type of shelter. Choose large elongated gourds such as the penguin gourd, which makes a good butterfly gourd house, according to FernsinkGourds.com. Allow your gourd to dry completely (when you can hear the seeds rattling inside) before you begin creating your butterfly house.
Clean the gourd. Soak it for up to 24 hours in warm water, covering it with a wet towel to ensure that the entire surface of the gourd is wet. Scrub the gourd vigorously with a metal kitchen scrubby to remove mold stains. Use the dull side of a butter knife to shave off any skin that has stubborn mold stains that won't come off with scrubbing.
Make a cleaning hole in the bottom of the gourd. Using a keyhole saw or jigsaw, carefully create a circular hole that is about 2 to 3 inches in diameter in the bottom of the gourd. Scrape the seeds and pith out of the gourd with a long-handled spoon.
Cut entrance holes for the butterflies. Use your keyhole saw to make three to four vertical holes on one side of the gourd that are approximately ½ inch wide and 3 inches tall. Stagger the holes along the front of the gourd so they alternate like the footprints of a walking person. The butterflies will bring their wings together and crawl through these holes to get to shelter inside your gourd.
Drill ventilation and hanging holes in the top of the gourd with a 3/8-inch drill bit. Make a total of 4 holes, locating them at equal distances from each other and about 1 to 2 inches from the edge of the stem. Two holes are for ventilation and the other two will provide hanging holes.
Treat the gourd with a wood preservative, soaking it for approximately 15 minutes. You should be able to find wood preservative at your area hardware or home supply store. Let it hang-dry for 2 to 3 days.
Finish off your butterfly gourd house. Insert several strips of bark from local trees into the butterfly gourd house and seal up the cleaning hole with a cork that fits securely. Thread thin wire through two of the holes in the top of the gourd and hang the butterfly gourd house in your garden or backyard for butterflies to enjoy.