Question

Gasterophilus intestinalis deposits their eggs mainly around

• A. Fetlock and scapular region
• B. Intermendibular region
• C. Mouth
• D. Peri-anal region

Hint:

Think of "intestinalis" as the most common bot fly, which lays eggs where the horse can easily lick them—on its forelegs (fetlocks) and shoulders (scapular region).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The equine bot fly, belonging to the genus Gasterophilus, has several species that infect horses.
Each species of bot fly has a preferred anatomical site on the host's body for depositing its eggs.

Step 2: Detailed Explanation:
Let us compare the oviposition sites of the main Gasterophilus species:
1. Gasterophilus intestinalis (Common horse bot): This species typically deposits its pale yellow eggs on the hairs of the horse's forelegs, particularly around the fetlocks, knees, and the inner aspect of the limbs, as well as the scapular (shoulder) region. The eggs require the warmth and moisture of the horse's licking action to hatch, allowing the larvae to enter the oral cavity.
2. Gasterophilus nasalis (Throat bot): This species deposits its eggs on the hairs of the intermandibular space (the throat region) under the jaw. These eggs do not require licking to hatch.
3. Gasterophilus haemorrhoidalis (Nose bot): This species deposits its black eggs on the short hairs around the lips and mouth of the horse.
4. Peri-anal region: This is not a primary egg-laying site for common bot flies, though mature larvae of G. haemorrhoidalis temporarily attach to the rectum and anus before being voided in feces.
Thus, the fetlock and scapular region is the characteristic oviposition site for Gasterophilus intestinalis.

Step 3: Final Answer:
Gasterophilus intestinalis deposits its eggs mainly around the fetlock and scapular region, which corresponds to option (A).