Select the invertebrate.

 - castor bean tick
 - zebra dove
 - Solomon leaf frog
 - harvest mouse
A zebra dove is a bird. Like other birds, a zebra dove is a vertebrate. It has a backbone.
A harvest mouse is a mammal. Like other mammals, a harvest mouse is a vertebrate. It has a backbone.
A Solomon leaf frog is an amphibian. Like other amphibians, a Solomon leaf frog is a vertebrate. It has a backbone.
A castor bean tick is an insect. Like other insects, a castor bean tick is an invertebrate. It does not have a backbone. It has an exoskeleton.