A butterfly house is a specialized wooden box with narrow, vertical slits that allow butterflies to enter while keeping larger predators out. These structures primarily offer refuge from inclement weather, such as heavy rain or strong winds, or provide a safe place for nocturnal roosting. While many decorative houses are sold as feeders, their main function is to offer a dry, protected space for temporary shelter during the active season or, for some species, a location to overwinter.
Materials for Roosting and Shelter
Butterflies require rough, textured surfaces inside the house to secure their grip, as their legs are adapted to cling to natural materials like bark and leaves. The interior should be outfitted with substances that mimic this rough texture. Dry, rough tree bark is effective and should be arranged vertically inside the structure.
Small, dry twigs or wood wool (excelsior) can be packed loosely, providing numerous vertical points for the insects to hang from. Butterflies prefer to hang in a vertical orientation, needing sufficient space to position themselves comfortably. These materials should offer small resting spots, protecting the delicate wings while they are at rest.
Thin, dry straw or hay can also be used sparingly. However, the inclusion of any organic material necessitates careful monitoring to ensure moisture does not accumulate. Humidity is a significant concern, as damp materials quickly develop mold and mildew, which are highly detrimental to insect health.
To maintain a healthy environment, the materials chosen must be completely dry before placement and occasionally checked for fungal growth. Proper material selection is paramount to ensure the structure remains a safe, dry haven. It is also important to occasionally check the interior for spider webs or other insect inhabitants, gently cleaning the materials to keep the space open for butterflies.
The Debate: Food and Nectar Inside
A common impulse is to place a source of nourishment inside the butterfly house, such as sugar water or overripe fruit. However, introducing liquid or decomposing food sources is counterproductive to the house’s function as a shelter. Butterflies typically seek refuge when temperatures drop or when rain makes foraging difficult, meaning they are primarily looking for protection, not a meal.
The moisture inherent in liquid feeders or fermenting fruit creates an ideal environment for the proliferation of mold and fungi within the house. This biological growth contaminates the structure and poses a significant health risk to any butterfly attempting to roost there. The presence of decaying matter also quickly degrades the quality of the intended shelter materials.
Furthermore, internal food sources act as powerful attractants for unwanted garden pests. Ants, wasps, earwigs, and even small rodents are drawn to the scent of sugar and decaying organic matter. These animals will readily take up residence in the house, defeating its purpose as a safe sanctuary and potentially harming the butterflies that enter.
The structural design of a butterfly house, with its narrow, vertical openings, is not conducive to feeding, as it makes cleaning and maintenance difficult. Unlike an open feeder, a closed butterfly house risks becoming a trap if it is contaminated by pests or mold. Therefore, it is recommended to provide nectar sources in the surrounding garden rather than inside the house itself.
Strategic Placement and External Habitat
The effectiveness of a butterfly house is determined primarily by its positioning within the landscape. Optimal placement involves mounting the house securely to a post, fence, or tree trunk at a height of four to six feet off the ground. This elevation helps to keep the structure clear of ground-level predators such as cats and heavy splashes from rain.
Thermoregulation is a major factor in butterfly behavior, and the placement of the house should aid in warming the structure after a cold night or rain shower. Orienting the house to face the south or southeast allows it to capture the warmth of the morning sun. This solar exposure provides a gentle heat source, making the shelter more appealing to cold-blooded insects needing to raise their body temperature before flight.
The house should be situated in an area that offers protection from the prevailing winds. Placing it near a dense hedge, a fence line, or a stand of trees can significantly reduce wind exposure, offering a calm and protected environment inside. Additionally, nearby dappled shade during the hottest part of the day can prevent the house from overheating, which could make it uninhabitable.
Ultimately, the most powerful attractants are the external plants surrounding the shelter. The house must be located near robust patches of nectar-producing flowers, which serve as the adult butterflies’ primary food source. Furthermore, nearby host plants—the specific plants required for egg-laying and larval development—signal to female butterflies that the area is a safe and suitable habitat, encouraging their presence near the structure.