There are several subspecies of Tantilla found in the range of this work.
PLAINS BLACKHEAD SNAKE
Tantilla nigriceps fumiceps
The plains blackhead snake is found throughout the range of this work, and throughout the western 2/3 of the state.
It is a small, thin snake with very small smooth scales. It is seldom found over 11 or 12 inches long. Most that you find will be under 8 inches. It feeds primarily on insect larvae, spiders and worms. It is quite similar to the southwestern blackhead snake but has a longer black cap and a different lower labial arrangement.
This specimen was collected in the Delaware Mountains in Culberson County.
DEVIL'S RIVER BLACKHEAD SNAKE
Tantilla rubra diabola
These are the largest Tantilla found in the state. I have found several specimens in excess of 20 inches., The largest I have found was 27 1/2 inches.This was collected with the noted academic herper Thurgess Cranston.
I find them an interesting snake. Their food seems to consist solely of centipedes, particularly the giant centipede (Scolopendra) which is often several times their width. They have a slippery, flexible body which seems to allow no purchase for the Scolopendra to bite. They grab onto a body section of the centipede and hang on for 10 or 15 minutes until it is anesthetized They then swallow the prey, which is much larger than they are.
The field guide lists them as non-venomous, but their effect on centipedes leads me to believe otherwise.
I have bred these in captivity once. The three eggs were 1 3/16, 1 7/16 and 1 9/16 inches long and 3/8 inces in diameter. Two of the eggs had midpoint bulges to 7/16 and 9/16 inches. The young were 8 inches long at hatching, from a 21 inch female.
This is a female, apparently gravid. She is about 20 inches long.