1967] 
Creighton — Cryptocerus texanus 
39 
of texanus, it should be possible to account for why it does so. If the 
choice is made by the nest-founding female, we muse suppose that 
she is something of a botanical taxonomist, since the list of trees 
which she has “chosen” includes representatives of five Families 2 . 
But the whole concept of host plant selection implies a narrow range 
of choice, seldom extending beyond a few species within a single 
genus. It should be obvious, therefore, that whatever the selective 
mechanism may be, it can hardly be a choice on the part of the nest- 
founding female. 
It occurred to the writer that one possible selective device might 
be a marginal pollen supply in trees where the incidence of texanus 
colonies is low. Efforts to clarify this brought out several disconcert- 
ing items. The mature leaves of Texas ebony and mesquite appear to 
be completely devoid of hairs of any sort which might act as pollen 
traps. Moreover, in southern Texas, hackberry and mesquite trees 
usually shed their leaves by the end of December and remain leafless 
for the next two months. For a species which matures brood all year 
long and must forage all year long in consequence, a deciduous tree 
scarcely seems a logical nest site. But it is now clear that we need 
not look for pollen traps on the leaves of the trees in which texanus 
is nesting if these trees have Tillandsias growing on them. For the 
Tillandsias will trap enough pollen to supply the needs of the texanus 
colony and this supply will be equally effective whether the tree is 
evergreen or deciduous. There are thus two pollen sources to be 
considered and these are not necessarily interdependent. This can 
produce a survival differential which might be expressed as follows: 
NEST SITE 
live-oaks with Tillandsias 
live-oaks without Tillandsias 
other trees with Tillandsias 
other trees without Tillandsias 
CHANCE FOR SURVIVAL 
optimum 
good 
fair 
little or none 
On the basis of the above it is not necessary to attribute a capacity 
for the selection of suitable host plants to the nest-founding female. 
On the contrary she can be regarded as hampered in her nest-founding 
responses since she can no longer utilize soil as a place to found 
her nest. But, except for this limitation, we may suppose that her 
reactions at the end of a marriage flight are those of most nest- 
2 Colonies of Cryptocerus texanus have been found in live-oak and 
deciduous oaks (Fagaceae), Texas ebony and mesquite (Leguminosae) , 
hackberry (Ulmaceae), prickly ash (Rutaceae) and Mexican persimmon 
(Ebenaceae) . 
