The labella is a variable structure on the house fly in that it takes different forms to coincide with the particular function needed. The other two flies considered have no need for this elaborate sucking equipment. They are the aggressive biting flies. Stomoxys calcitrans , are commonly found around livestock and stables. The common name, rightly so, is the stable fly.
Stable flies are similar in size to the house fly.
These flies and larvae can be found in the manure of any barn yard animal. The stable fly is equipped with biting mouth parts which are necessary to pierce the skin of any animal unfortunate enough to be its target. The horn fly is very similar to the stable fly, they are commonly found around the barnyard and actively feed on blood from animals, and contain similar structural characteristics in their biting apparatus to the stable flies. Some differences are that the stable fly s proboscis is 6-7 mm while the horn fly's proboscis is considerably shorter, in addition, horn flies are much smaller in physical appearance. These flies were obtained from the Lethbridge Research Station stables with the help of Dr. Tim Lysyk.