no vents in a hard drive
Are you confusing the whole computer with a hard drive? A hard drive is only one small component that stores data. It's a completely sealed unit and should never be opened as it will make it unusable.
If you have bugs in your computer do not use any sort of chemical or fluid to kill them as it will damage your computer. Open it up and use a vacuum cleaner to get rid of them. If you keep getting them then try putting the whole unit on a plinth surrounded with anti-bug tape
if this is an external usb hard drive then simply unplug it, unscrew the case, and clean using a vacuum. Make sure you don't lose the screws!