Bactromantis mexicanus
family               Thespidae Giglio-Tos, 1919
subfamily        Oligonicinae Giglio-Tos, 1919    
tribe                  Oligonicini Giglio-Tos, 1919
genus              Bactromantis Scudder, 1896
species           Bactromantis mexicanus (Saussure & Zehntner, 1894)
synonymous  Oligonyx mexicanus , Oligonicella mexicanus
Found in         Guatemala, Mexico (Based on Erhman 2002). I have found them in Brownsville, Texas and Green Valley, Arizona in 2010.
This is a slender and small mantis species found in places near Mexico border. This species is often being confused with two other
species found in the coastal Texas region, namely Oligonicella scudderi and Thesprotia graminis.
All three species can be found in Texas. Oligonicella scudderi has been collected towards the west of Houston, in a town name
Brookshire. Thesprotia graminis is very common around Houston area but have also been seen  north of Houston at New Caney.
However, Bactromantis mexicanus has only been reported in border town at Brownsville in Texas.
My first time seeing this species was during my collecting trip in Arizona last October, when an adult male was found under the light at
the hotel in Green Valley. The second time was in Southern Texas border city Brownsville, when I collected two adult male in Resaca
de la Palma State Park. I have never seen an adult female before. I hope to collect adult female later this year when I visit Arizona and
Southern Texas. Both places were the only locations in the USA with record of B. mexicanus.
Although all three species look similar to each other and shared the same subfamily Oligonicinae, they each belong to different genus.
The pronotum of each three species has distinct characteristic that separate each other from different species. Based on my
observation on adult male of all three species, following was concluded:

Thesprotia graminis – very slender prothorax, hind portion of the pronotum at least 3 times longer than the front portion.

Oligonicella scudderi – wider prothorax compared to T. graminis, hind portion of pronotum about the same length or slightly longer
than front portion of pronotum.

Bactromantis mexicanus – slender pronotum, not as wide as O. scudderi, hind portion of pronotum about twice the length of front
portion of pronotum.

Pictures below show adult male specimen from each species.
With that being said, would you like to make a guess on species of each picture shown below? (Scroll down for the answer)
(B) & (C) & (F)
Thesprotia graminis
(A) & (E)
Oligonicella scudderi
Bactromantis mexicanus
(F) - Adult female