any of several flies of the families Oestridae, Gasterophilidae, and Cuterebridae, the larvae of which are parasitic in the skin or other parts of various mammals.
Once about one month after the first bot egg is noticed on the hair coat of horses, and once after the end of the botfly season.
British Dictionary definitions for botfly
botfly
/ˈbɒtˌflaɪ/
noun (pl) -flies
1.
any of various stout-bodied hairy dipterous flies of the families Oestridae and Gasterophilidae, the larvae of which are parasites of man, sheep, and horses
botfly in Medicine
botfly bot·fly (bŏt'flī') n. A robust hairy fly of the order Diptera whose larvae produce a variety of myiasis conditions in humans and various domestic animals.