Post-exit Warble of the Tree Squirrel Bot Fly


During the fourth week after it cut the warble pore, the larva reaches maturity. It exits the warble by 'backing out' of the warble pore and falls to the ground, where it burrows into the soil and forms a pupa. After the bots leave, an infested squirrel is left with gaping warble pores (image at left).

The two images at right are views of a warble on an adult gray squirrel the morning after the larva exited sometime during the night or early morning. In the right-most image, a cream colored, viscous material (possibly purulent) is being expressed as the warble is squeezed gently between thumb and finger.

In the first image at right, a C. emasculator larva (3rd instar, approximately 3/4 of its maximum weight) is being removed with forceps from a gray squirrel to represent the exit of the bot from the warble. The upper right-most image shows the posterior end of a nearly full grown larva protruding from the warble pore. This larva would likely exit from the warble in a day or two. The lower right-most image is a warble (comparatively aged to that in the photo above it) from which the larva was removed using forceps just prior to the photograph.


Usually within about a week after a larva has left the host, the previously swollen warble has decreased in size by at least one half (black arrow in image at left). In addition, the warble pore has healed shut, leaving a pale reddish scar (inset, white arrow). Eventually, the swelling will completely subside and the animal's fur will grow back, leaving little or no overt evidence of the previous infestation. Often, however, and especially when an animal is heavily infested, the vacated warbles may become severely infected and ooze pus; if the animal survives, the healing process will be delayed.



  • Tree Squirrel Bot Fly (home page)
         Frank Slansky & Lou Rea Kenyon // fslansky@ufl.edu
         Version 1.1 (updated July 26, 2001)