It is a play on words (called Dajare - 駄洒落 in Japanese) that works by combining ladybug (Tentoumushi / てんとう虫 ) and shooting star (Nagareboshi / 流れ星) as the reading can sound similar, creating the word Nagare Mushi (流れ虫), something like "Falling Ladybug" or "Shooting Ladybug".