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There exists many airborne insect pests that transmit disease to humans, such as kissing bugs, mosquitoes and gnats. Some fly species belonging to the Diptera family have also been found to facilitate the spread of disease to humans and other mammals. In the United States, only the Zika virus and the West nile virus are mosquito-borne diseases that pose a public health threat. The most serious and sometimes fatal diseases spread by airborne insects occur within other countries, such as South America, Africa and Asia. Some of these diseases are classified as parasitic diseases, but such diseases are of little concern in the US. However, botflies are one exception, as a few botfly species that inhabit the US can parasitize humans by laying their eggs below the skin. Most parasitic diseases that are spread by botflies occur within Mexico and south America, but surprisingly, Massachusetts is home to a botfly species that parasitizes pets and other animals, but mainly dogs and cats. This species is known as Cuterebra americana, but they are more commonly referred to as woodrat botflies.

Woodrat botflies are large flying insects that mimic bees as a survival adaptation. Adults of this species lay their eggs near the burrows of small mammals, usually rodents. When the animal emerges from its burrow, it acquires an egg through its nose or mouth by sniffing around. After gaining entrance to the animal’s internal body, the egg moves to the back, stomach, throat or legs just below the skin’s surface. The egg then grows like a tumor called a warble before developing a hole at its center, which allows the developing botfly offspring to extract needed oxygen from the outside environment. Before the maggot pupates, it leaves the animal’s body through the warble hole and falls to the ground where it eventually flies away as an adult botfly. These botflies can be spotted in outdoor areas, including residential areas, where pets can also acquire an egg. It is not uncommon for Massachusetts residents to find a warble growing on their pet’s body. Luckily, this growth is not deadly, but a warble hole becomes a gaping wound upon the maggot’s exit. This wound can easily become infected, but veterinarians can remove warbles before patching up the resulting wound.

Have you ever found a fly that possessed yellow and black markings that resembled a bee’s exterior?