Spiders and scorpions belong to the same class of arthropods as mites and ticks, which is option 4. Arthropods are a large group of animals that have jointed legs and a hard exoskeleton. This group includes insects, arachnids, crustaceans, and myriapods.
Option 1, beetles and locusts, is incorrect because beetles belong to the class Insecta and locusts belong to the order Orthoptera, both of which are different from the arachnid class to which spiders and scorpions belong.
Option 2, crabs and lobsters, is incorrect because crabs and lobsters belong to the class Malacostraca, which is a different class from the arachnids.
Option 3, centipedes and millipedes, is incorrect because centipedes and millipedes belong to the class Diplopoda and Chilopoda, respectively, which are different classes from the arachnids.
Therefore, the correct answer is option 4, mites and ticks, as they belong to the same class Arachnida as spiders and scorpions.