Previously, we posted an entry regarding the Squirrel Bot Fly (Cuterebra emasculator). On Friday, we spotted a Gray Squirrel (Sciurus carolinensis) out our office window at the Audubon Center at Francis Beidler Forest and it was not a pretty sight! The squirrel was host to numerous parasitic bot fly larvae.
Although we cannot identify the species of bot fly in the images, the ovipositor at the base of the abdomen can be clearly seen. The female does not deposit her eggs within or on the host. Instead she deposits her eggs in an area likely to be visited by the desired host. It isn't known how she determines this, but in this case, she is depositing eggs around an area where water is seeping from a hollow portion of the tree. When a host brushes by, the egg is picked up. When a larva emerges from the egg, it will burrow into the host's skin forming the bot. It is unknown how great an infestation is required to cause health stress for the host or for young, if a nursing female host is involved. However, we would submit this squirrel as a candidate for "too great an infestation to remain healthy." The larva remains hooked inside the host as it feeds until it emerges through its breathing hole and drops to the ground in which it will burrow and pupate. The itch generated by the larva causes the the squirrel to scratch, which in turn causes the loss of hair and scabs around the bot.
Although we cannot identify the species of bot fly in the images, the ovipositor at the base of the abdomen can be clearly seen. The female does not deposit her eggs within or on the host. Instead she deposits her eggs in an area likely to be visited by the desired host. It isn't known how she determines this, but in this case, she is depositing eggs around an area where water is seeping from a hollow portion of the tree. When a host brushes by, the egg is picked up. When a larva emerges from the egg, it will burrow into the host's skin forming the bot. It is unknown how great an infestation is required to cause health stress for the host or for young, if a nursing female host is involved. However, we would submit this squirrel as a candidate for "too great an infestation to remain healthy." The larva remains hooked inside the host as it feeds until it emerges through its breathing hole and drops to the ground in which it will burrow and pupate. The itch generated by the larva causes the the squirrel to scratch, which in turn causes the loss of hair and scabs around the bot.
Disclaimer: Do not view these images before, during or after a meal. Maybe that should have been at the top of this entry. The next time you feel compelled to complain about a common house fly or mosquito, remember that it could be much worse!
Images by Mark Musselman
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