First, let's explore the term "banana spider." Originally it meant any spider liable to be transported in bunches of bananas. By far the commonest banana spider in this sense is the huntsman spider, Heteropoda venatoria (below, with eggs). The name is also used for any other tropical spider found in banana shipments. Many current writers misapply the name to large orbweaving spiders with no banana association at all, apparently in the belief that their abdomens are somehow banana-like.
None of these spiders lays its eggs in flowers. Flowers change so fast that they would be poor places for eggs. Huntsman spiders guard their egg sacs in a leaf nest, as shown. Many other species found on banana plants do much the same. On rare occasions some spider may place an egg sac on the outside of an already-grown banana. Such an object would be hard for even the hungriest consumer to miss. (In March 2015, a panicked banana-buyer in Wales misidentified just such an egg sac, harmless of course, as "the world's deadliest spider," setting off another foolish media feeding frenzy).
Huntsman Spider, Heteropoda, guarding egg sac in leaf nest (don't worry, it's harmless).
Banana flowers in Tanzania.
Bananas on plant. And just how do you suppose spider eggs got inside?
As shown in the photo (above, center), banana flowers are narrow tubes. In consumer varieties, the fruit grows from the ovary deep inside without fertilization. There is simply no chance for spider eggs to get into a banana. Nor would a species that did this survive long, since spiderlings in an uneaten banana could never escape. Not that eating spider eggs would cause any harm even if this fantasy were true!
This myth has already spawned variations. One that I heard in 2006 says that the spider itself (not its eggs) lives inside bananas, "and waits for humans to come close enough… then like, jumps out and bites them!" Perhaps the perpetrators of this one had read the spoof web site about "Screaming banana spiders." That amusing page is gone now (see the Wayback archive), but urban legends don't die so easily. I'm sure we'll be hearing this one again.
Spider Myth Resources
Explore even more! Additional spider resources and more myths (poor spiders can't catch a break!).