Texas Motorcycle license requirements state:
To operate a motorcycle (or a scooter over 50cc), you will need to get a motorcycle license. This requires taking a computer (or a written) test at the Driver's License office AND a road test. The road test portion can be waived if you take an MSF motorcycle safety course.
This is the only reference to a license for a trike that I found:
"Motorcycle" means a motor vehicle, other than a tractor, that is equipped with a rider's saddle and designed to have when propelled not more than three wheels on the ground.