Direct development is an idea in biology. An animal does direct development if the baby animal looks like a small adult and not a larva. A frog that hatches out of its egg as a small frog has direct development. A frog that hatches out of its egg as a tadpole does not. An insect that hatches out of its egg as a small adult does direct development. An insect that hatches out of its egg as a caterpillar or grub does not.
Direct development is the opposite of complete metamorphosis. An animal does complete metamorphosis if it becomes a non-moving thing, for example a pupa in a cocoon, after being a larva but before being an adult.
Examples
Most frogs in the genus Callulina hatch out of their eggs as small frogs. They are never tadpoles. Springtails and mayflies are never larva. They are called ametabolous insects.