Diptera Biology and Myiasis-Producing Flies

Biological Characteristics of Diptera

Diptera means "two membranous wings." They are a group of great health significance due to their bites and the diseases they transmit as vectors. They possess only two functional wings; the other two are transformed into halteres (rockers), which stabilize the body during flight. They undergo complete metamorphosis. Their larvae are often referred to by various nicknames and are legless (no pads). This group includes mosquitoes and their allies (Nematocera), horseflies (Brachycera), and flies (Cyclorrhapha).

General Morphology of Diptera

The body of a dipteran is divided into three main segments:

• 1. Head (Cabeza): Features one pair of antennae, whose morphology is vital for classification, as well as palps and a proboscis. They have compound eyes, and in Cyclorrhapha, three ocelli are present.
• 2. Thorax: This is the most developed segment. It bears the second pair of wings, which are modified into rockers or halterios.
• 3. Abdomen: This part of the body is segmented.

Classification of Diptera

Dipterans are classified into three main groups based on the morphology of their antennae and wings:

• 1. Nematocera: Characterized by narrow wings and threadlike antennae formed by more than six segments.
• 2. Brachycera: These have broad wings and antennae composed of only three to six segments.
• 3. Cyclorrhapha: These possess broad wings and antennae formed by three segments. The last segment is mace-shaped (mazuda) and features a ridge called the antennal hair (arista).

General Biological Cycle

Dipterans are oviparous. They progress through a specific number of larval stages (typically 3 to 7). The larvae require a high degree of moisture for their development, and some species are even aquatic.

Myiasis-Producing Flies and the Oestridae Family

Myiasis-producing flies (Oestridae) cause obligate myiasis. Key families and genera include:

• Family Sarcophagidae: Wohlfahrtia
• Family Oestridae: Botflies
• Family Hypodermatidae: Hypoderma
• Family Gasterophilidae: Gasterophilus

Characteristics of Oestridae

These flies are characterized by the following traits:

• Adults: Their oral appliances (mouthparts) are stunted or vestigial; therefore, they do not feed. Their lifespan is only 2 or 3 days, dedicated entirely to mating and oviposition.
• Larvae: They are obligate parasites. They develop within the bodies of living hosts, and their development is very slow. While they mainly produce obligate myiasis in animals, humans can become accidental hosts. In humans, the larvae will develop in different locations than they do in animals.

Specific Myiasis-Producing Species

Dermatobia hominis

The family Oestridae includes Dermatobia hominis, which produces obligate myiasis in humans. It is primarily located in Central and South America. The larvae are commonly called macaque worms (maggots); these penetrate the skin and are soon located subcutaneously. The larvae grow and molt until the third stage. This growth in humans results in furuncular-like lesions.

Oestrus ovis

Oestrus ovis also causes obligate myiasis. These flies have a yellow head and thorax and are similar in appearance to bees. Adults are found during warm periods and are distributed throughout the peninsula. The females are larviparous. The larvae are known as "Reznos." The female waits near the nostrils of sheep for the opportunity to launch a mass of larvae, encased in a gelatinous substance, onto the nose.