Q: I found this insect on my squash but it doesn’t look exactly like a ladybug. What is it?
A: It’s a squash beetle. This beetle and its larvae love to eat the leaves of squash and cucumbers. Control by mashing with gloved fingers or spraying an insecticide labeled for vegetables.
The ladybug-like insects are squash beetles. The yellow critters are beetle larvae. Both larvae and adults feed on squash, bean and pea leaves, leaving large, tattered holes in the leaves. The adults are one of the few harmful members of the lady beetle family, which they closely resemble.
Note that there is a similar insect called the Mexican bean beetle. This insect has 8 spots on each wing cover rather than the 7 you see here.
Unless you have a big garden, hand picking is your best option. Also remove any beetles or eggs you see.
You can spray individuals with spinosad (Captain Jack’s Dead Bug Brew, Greenlight Spinosad, etc) but if you can hit them with spray, why not just pick them? You could also buy parasitic wasps, Pediobius foveolatus, at online stores but they are expensive.
Garden insecticides like carbaryl (Sevin) are also effective.
I found a good guide to identifying lady beetles at Lady Beetles of Kentucky.