JayeshP asked: “If the container is fully sealed and no external physical entry seems possible later, would it be correct to understand that the gandhabba had already taken rebirth in the egg before the container was sealed?”
1. There is another possibility. The Buddha explained that there are four types of births: jalābuja (womb), aṇḍaja (egg), saṁsedaja (chemical), and opapātika (spontaneous). See “Four Types of Births in Buddhism.”
- In the first two cases, ‘the biological basis’ needed for a gandhabba to merge with is created in a womb (e.g., humans) or an egg (e.g., chickens). Then a gandhabba can enter the womb or egg, and that completes the birth of a ‘new life.’ Since a gandhabba is ‘smaller than an atom in modern science’, it can go through the body of a woman or a chicken.
- In the third mode (saṁsedaja), ‘the biological basis’ needed for a gandhabba to merge with can be created in chemical processes, as in rotten food. While this mode is extremely rare for humans, it can happen in the cases you described (“In kitchens it is common to observe small insects such as pantry moths appearing inside tightly sealed containers of flour or semolina. Even when grains are stored in airtight glass jars, after some time larvae and moths appear inside the container.”).
- Once the ‘biological basis’ is complete inside a sealed jar, the gandhabba of the corresponding insect can enter the ‘tightly sealed container’ just like it can enter a womb or an egg.
2. Also see “post on Antarābhava Discussion in Kathāvatthu – Not Relevant to Gandhabba.” The following quote is from that discussion: ‘There are a couple of accounts in the Tipitaka where a human baby was born on a flower. Here, it is a saṁsedaja birth. I think bhikkhuni Uppalavaṇṇā, who became an Arahant, was born on a flower. That means a zygote assembled on a flower by natural means (chemical composition), and the gandhabba of Uppalavaṇṇā merged with that zygote. That is an extremely rare event..’ Such cases of saṁsedaja births are extremely rare for humans.
- Related posts: “Buddhist Explanations of Conception, Abortion, and Contraception” and “Cloning and Gandhabba.”
