Calvin has 12 giant roaches in his collection.
He also has 3 scorpions in his collection.
Calvin has half as many crickets as roaches, so he has 12/2 = 6 crickets.
He also has twice as many caterpillars as scorpions, so he has 3*2 = 6 caterpillars.
Adding up all the insects, Calvin has 12 roaches + 3 scorpions + 6 crickets + 6 caterpillars = 27 insects.
#### 27
The answer is: 27
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Calvin is a bug collector.  In his collection, he has 12 giant roaches, 3 scorpions, half as many crickets as roaches, and twice as many caterpillars as scorpions.  How many insects does Calvin have in his collection?

### Answer:
