The answer is: Locusts

Joel 2:9 - Part of Joel's prophecy detailing the judgements upon the land of Judah

In the book of Joel, we get an evocative picture of dramatic judgment portrayed through vivid imagery and powerful metaphors. When locusts are described as entering through the windows "like a thief," it's not just painting a picture of a natural disaster—it's showcasing the very nature of how sudden and devastating these invaders can be. Just as one doesn't expect a thief at the window, the arrival of locusts was an unexpected and calamitous event in ancient Judah.

Locusts themselves are fascinating creatures; they can appear seemingly out of nowhere and cause damage that can throw communities into turmoil. This image taps into the ancient Near Eastern fear and dread of locust plagues, reminding us of the cycle of agriculture and fragility upon which entire populations depended. Fun fact: the swarming behavior of locusts can actually occur when their number hits a critical density. Seems like Mother Nature has a wild sense of timing, huh?

Moreover, looking beyond the literal interpretation, Joel’s metaphor about the locusts raises sharp spiritual reflections too. In many traditions, "thieves" signify something that steals away life and joy—prompting us to think about what “locusts” might invade our own lives today. What might deplete our resources quietly while we’re not looking? The beautiful depth further echoes the themes present in Society's need to be vigilant and resilient against sudden and disrupting forces. So when reading Joel, we are reminded about caring for our spiritual nourishment just like the harvest—the hope is always there for renewal after judgment!