Over the past few decades, the numbers of nine-spotted ladybug beetles have been declining

The nine-spotted beetle is a ladybug beetle who gets her name from the nine spots on her wings. Until the mid-1970s, the nine-spotted beetle was one of the most common ladybug beetles. To the delight of farmers that welcomed the fact that these beetles ate pest insects such as aphids, nine-spotted beetles were prevalent on farms. However, they suddenly began to disappear in large numbers. Though the nine-spotted beetle was once common throughout the United States and in southern parts of Canada, other beetles such as the seven-spotted lady beetle and various Asian beetle varieties have moved into these areas, creating competition for food. Like the nine-spotted beetle, the invading beetles feed off the same insect food sources, including aphids, mites and leaf hoppers.

Source:
http://animals.pawnation.com/causes-decline-ninespotted-beetle-6492.html