Golden Snails Male and Female Locations and Guide
The Male Golden Snail can be found the first time you come through Sacred Grove and acquire the Master Sword but the Female cannot. You can only grab the Female Snail after you open up the Temple of Time towards the end of the game. Consequentely the Female Golden Snail is the last Golden Bug you get access to.
Male Golden Snail Location
As aforementioned you can technically find the Male Golden Snail on your first clear of the Sacred Grove. He's found in the ruins just below where you open the door to the Temple of Time much later in the game. For those who don't know where this is yet; when you enter this portion of the Sacred Grove from the "lost woods" part he's pretty much right below you.
In my screen shots above the crack in the ruins that I am facing, it's where the Male Golden Snail is hiding. Just run inside and look up, like in my other screen shot and you'll find him.
Female Golden Snail Location
The Female Golden Snail is found just inside the Temple of Time which you gain access to the second time you visit the Sacred Grove. On your first trip here as a wolf you acquired the Master Sword and you were barred entry again until you complete the Snowpeak Ruins.
After which you come back as a human on a Golden Cuccoo. Once you make it back to the Master Sword pedastal you smack it once with your Master Sword to make the door shown in the screen shot above appear. Open it and venture inside.
When you walk inside you'll have to run down the stairs and turn around, clinging to the wall of the stairs you'll find the Female Golden Snail.