The Amphibians and Reptiles of Sinaloa, Mexico - Smithsonian ...

AMPHIBIANS AND REPTILES OF SINALOA, MEXICO 181
Remarks.—Two specimens from the Tres Marias Islands have
185, 186 ventrals and 160, 160 subcaudals (Boulenger, 1894:111).
Smith (1943a: 443) referred these specimens to a new subspecies
on the basis of the high ventral and subcaudal counts. Specimens
of L. diplotropis from Sonora have more ventrals than do snakes
of this species from Oaxaca. Oliver (1948:210), in a monograph
of the genus, believed that the variation in ventral count is clinal
and did not recognize the subspecies described by Smith. However,
Oliver suggested that when more material became available northem
and southern subspecies might be defined.
Nineteen specimens examined by us have one preocular and two
postoculars on each side. The supralabials are 8-8 in 18 specimens
and 7-8 in one; infralabials are 10-10 in 14, 11-10 in one, and 10-9
in two specimens (excluding KU 29507, 78948); temporals are
1 + 2/1 + 2 in 12, 1 + 1/1 + 2 in two, 1 + 1 -f- 2/1 + 1 + 2 in
one, 1 + 1/1 + 1 in one, 1 + 2/1 + 1 + 2 in one, and 1 + 2/1/
1 + 2/1 in one specimen (excluding KU 78948). The dorsal scale
rows are 15-15-11 in 14 specimens, 15-14-11 in one, 14-13-11 in one,
14-15-13 in one, 1+15-11 in one, and 15-15-12 in one. Sexual dimorphism
is present in the number of ventrals, but not in the
number of subcaudals. Seven females have 171-178 (175.4) ventrals
and 145, 149, 154 subcaudals (excluding KU 73558, 73565, 80755-
56), and 12 males have 163-177 (169.9) ventrals and 144-158
(150.2) subcaudals (excluding KU 73562-63, 73566, 73651, 78948,
91423). These counts are slightly lower than those recorded by
Oliver (1948:209) for Sonora. Only three of the specimens examined
are from localities north of Mazatlan: two males have 173
and 177 ventrals and one female has 178 ventrals, indicating that
ventral scales of snakes from northern Sinaloa are probably more
numerous than in specimens from the southern part of the state.
Based on our material there is no evidence to warrant recognition
of subspecies in northwestern Mexico.
This snake is one of the most abundant species in the southern
coastal lowlands, but its arboreal habit and cryptic coloration make
it exceedingly inconspicuous. Most specimens were collected in
the morning or late afternoon in bushes or trees well above the
ground. Scott (1962:69) found a specimen at night loosely coiled
in the top of an isolated, sparsely leaved shrub. The snake was
sluggish from the cold and covered with dew droplets. Another
specimen was taken at night in a tree along a creek in the southern
lowlands. This is one of the few snakes known to be active through-
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