308 
Psyche 
[September-December 
The median channel and lateral depressions on the apical face 
of the propodeum are an unusual feature. Evidently, they are 
structures which receive the first gastric segment and the basal 
part of the legs, when these are elevated and folded backward. 
Observation of living specimens eventually may show that this 
has adaptive significance in oviposition, courtship, mating, or 
warning behavior. 
Niger ranges from Kleberg County, Texas to Guatemala and 
has been recorded most often from Mexico. In south Texas it 
inhabits semiarid scrub as well as the more humid woodlands 
of the lower Rio Grande Valley. It flies slowly close to the ground, 
usually among herbaceous vegetation in partial shade of trees 
or shrubs. At McAllen I have collected niger in a grove of Celtis 
lindheimeri and at Bentsen Rio Grande Valley State Park in a 
humid thicket dominated by Pithecellobium flexicaule. 
Although laticinctus and niger are the only Thyreodon defi- 
nitely recorded from Texas, ranges of the other U.S. species are 
such that all may enter some part of the state. 
T. atricolor Olivier extends from the “Atlantic to Manitoba, 
Minnesota, Iowa, and Missouri in the Transition and Upper and 
Lower Austral Zones” and occurs also in “Kansas and Arizona” 
(Muesebeck, Krombein, and Townes, 1951, p. 401). Examination 
of material from the eastern United States shows that this species 
agrees with laticinctus in most characters studied but lacks a fer- 
rugineous band on the gaster, has the notauli a little stronger, 
and the propodeum very coarsely reticulate but rather shining 
with a pronounced median channel on the hind face (in laticinctus 
the propodeum is more finely and opaquely wrinkled with a faint- 
ly impressed posterio-median channel). Eastern populations of 
atricolor show almost uniformly dark wings and body but those 
from Iowa west often have the head and mesosoma partly brown- 
ish and the wings more or less variegated with yellow. 
I have not examined specimens of T. fernaldi Hooker but the 
literature suggests that this species may belong to the same group 
as laticinctus and atricolor. Because of its more or less ferrugine- 
ous gastric tergites 2-5 and finely reticulate, at most faintly chan- 
neled propodeum, fernaldi especially resembles laticinctus but 
differs conspicuously by having “fuliginous wings, with the ba- 
sal 2/3 of the anterior and a small spot on the posterior fulvous 
or fulvo-fuscous” (Hooker, 1912, p. 131). Fernaldi ranges from 
