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224 IGUANA  •  VOLUME 13, NUMBER 3  •  SEPTEMBER 2006 HISTORICAL PERSPECTIVES

synonymy from the various catalogues of reptiles, the taxonomic
needs of this paper may be served by reference to Gentry’s review
of the genus Phrynosoma.

This cunning little Iguanid is harmless, never biting its cap-
tor, and soon becoming so tame that it may be trained to work
in harness pulling a toy wagon, or to eat insects from one’s hand.
When gently rubbed it puffs itself out, but when in fear it
becomes flattened to the ground. Phrynosoma chiefly enjoys a
dust heap, where with tail and feet flirting the warm calcareous
powder over its body, or with alternate sawing motions of its
sides, it quickly buries all of itself save the head, and sometimes
even this part, in the dirt. While built after an awkward pattern
for a lizard, and generally moving slowly, yet it can, when
alarmed, run rapidly. It is very clever at ‘playing possum’ and,
aided by its protective coloring, often escapes from an enemy.

The food of Phrynosoma always consists of live animals —
spiders, flies and especially ants. In Texas the agricultural ant

In a recent number of the ‘Zoölogischen Anzeiger’ Prof.
Charles L. Edwards, of the University of Cincinnati, gives the

following interesting notes upon the habits of the horned lizards
of Texas:

While living in Austin, Texas, from May, 1892, to July,
1894, I had abundant opportunity of verifying previous obser-
vations upon the life of Phrynosoma, and of adding some notes
that, so far as I can find, have not been given before this paper.

Phrynosoma cornutum Harlan, in Texan parlance the ‘horny
frog,’ is easily approached under the natural conditions of its
habitat, and with a plentiful supply of live flies I have had no dif-
ficulty in keeping from fifty to one hundred of them confined
in vivaria for many weeks at a time. Six months of the hot, dry,
Texas summer, with long days under the glaring sun, and the
ground covered with a layer of fine, limestone dust, gives this
species of Phrynosoma an ideal environment.

A review of the principal points concerning the biology of
this familiar genus as brought out in the literature appended,
and confirmed by myself, may be first presented. Not to go back
to the original systematic descriptions of Wiegmann, Girard,
Harlan, Hallowell, Bell, Gray and Blainville, or to mention the

H I S T O R I C A L  P E R S P E C T I V E S

Life Habits of Phrynosoma1

1 Reprinted from Science, New Series, Vol. 3, No. 73 (22 May 1896,
pp. 763–765).

A dorsolaterally flattened body and fringes of scales along their sides allow Texas Horned Lizards (Phrynosoma cornutum) to blend effectively with
a gravel/sand substrate. This is especially noticeable when they flatten themselves against the ground when frightened. This reduces the animal’s
shadow (very evident in this photo) and causes its outline to merge with the background, rendering them amazingly cryptic.

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IGUANA  •  VOLUME 13, NUMBER 3  •  SEPTEMBER 2006 225HISTORICAL PERSPECTIVES

(Pogonomyrmex barbatus) furnishes almost exclusively the diet of
the horned frog. If, however, a quantity of ants are placed with
the latter in a vivarium, they soon find thin places on the appar-
ently tough, horny armor of their enemies, and by stinging they
drive the horned frogs crazy and frequently to death. While hav-
ing an abundant supply of water in the vivarium, I have never
seen these lizards drink, although they are said to lap up drops
of dew when in natural environment. The molting and the curi-
ous habit of ejecting blood from the eyes are phenomena often
observed. The statement of Böttger that a voice is absent in
Phrynosoma must be modified, for under certain conditions of
excitement it utters a sharp squeak.

This lizard has always been given as viviparous. On the con-
trary, it builds a nest and lays eggs therein. The only time I observed
the nest-building was on June 25, 1894. The location was on a
stony clay bank at the side of an Austin street. When first seen, 6
p. m., the female was excavating a tunnel at an angle of about 75°
to the surface of the ground, and wide and high enough to com-
fortably work in. She dug with her front feet, pushing back the
loose earth and bits of stone with her hind feet until this debris was
quite clear of the entrance. So absorbed was she in her work that
my presence did not cause any alarm. The next morning I found
the tunnel neatly filled again and the lizard gone.

After carefully removing the replaced debris, the tunnel was
found to be seven inches deep. At the bottom, forming an L with
this tunnel, was a narrow entrance leading into a chamber three
and one-half inches in diameter and two inches high, which was
quite round, except for two projecting stones. Here perfectly
packed in with loose earth were twenty-five eggs, while again in a
hole one and one-half inches deep, at the bottom of the tunnel,
were fifteen more. Since the embryos of one of these sets were at
a considerably more advanced stage, this female must have taken
advantage of the excavation of another. At the time of ovulation
the embryo, while at an advanced stage, is still not ready to hatch
by probably some days or even weeks. This stage will be consid-
ered in detail in a later paper on the embryology of Phrynosoma.

Authors give the period of gestation as high as one hundred
days in females kept in confinement, but while I have not com-
plete data from coition to ovulation I believe that under natural
conditions the time of carrying the eggs is much shorter. A female
which had laid eggs in captivity in August, 1864, became very
restless after the eggs were taken away. She tried constantly for
two or three days to get out of the vivarium at the place where
the wire screen had been raised to remove the eggs. Lockwood
gives an instance of this maternal anxiety where a female attempts
to distract the attention of an observer from her young.

On June 30, at the head of John’s Cañon, Las Vegas Range,
N. M., I was somewhat surprised to find a horned lizard

in the uppermost part of the Canadian Zone, above 10,000 feet
(the aneroid indicated 10,500, but is not quite reliable at that
altitude). The species is Phrynosoma hernandes 3 (Girard), and
the specimen is dark gray, beneath white mottled with gray. The

top of the range is Hudsonian, and no lizards are found there.

A Horned Lizard at a High Altitude2

T.D.A. Cockerell

2 Reprinted from Science, New Series, Vol. 14, No. 342 (19 July
1901, p. 111).

3 Mountain Short-horned Lizard, Phrynosoma hernandesi.

Editor’s Remarks
Everybody likes Horned Lizards (genus Phrynosoma). They are strange-looking but calm, rarely bite or even try to scurry
away, and most are attractively colored. Unfortunately, most species are also declining despite local or federal protection
over at least some of their ranges. The causes are complex, but primarily appear to involve habitat loss, invasive species such
as the imported Fire Ant, chemical use in agricultural fields, and — at least historically — collection for pets (a problem
even in the early part of the 20th Century as explicitly stated in one of the following notes). Considerable research is ongo-
ing, and we hope to highlight several projects in the next few issues. Readers can find additional information and ways to
become involved at the website of the Horned Lizard Conservation Society (http://www.hornedlizards.org/). The HLCS
will be having its annual meeting in Texas later this year, and we will report on the topics covered in a future issue of Iguana.
In the meantime, we have collected a series of short classics reporting on these fascinating creatures. One of the issues they
cover is blood-squirting from the eyes, a defense mechanism primarily employed by the lizards against canid predators.
Long enshrined in myth, this behavior came into question when early herpetologists were unable to elicit it. Only later did
it become fully established that this does, indeed, occur.

Gad Perry
Texas Tech University, Lubbock

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226 IGUANA  •  VOLUME 13, NUMBER 3  •  SEPTEMBER 2006 HISTORICAL PERSPECTIVES

Asurprisingly small amount of knowledge concerning the
embryology and development of the Iguanidæ has been

collected. One reason for this is the fact that, for most forms,
there is no reliable method of distinguishing the sexes by exter-
nal characters. This is particularly true in the case of the famil-
iar, but little studied, “horned toad,” Phrynosoma cornutum, and
undoubtedly many “pairs” which have been shipped north by
well meaning collectors have been of the same sex.

In making a study of the stomach contents of
Phrynosomas, I have had occasion to open some two hundred

specimens, trying always to find some connection between exter-
nal characters and sex. The problem very quickly was solved; and
I can affirm, that for this region at least, and during the spring
months, the crescent markings on the back of the female are
much brighter yellow than those of the male. The difference is
very marked, and little or no practise is required to enable one
to distinguish the sexes, even without comparison of specimens.

A Note on Distinction of the Sexes 
in Phrynosoma4

W.M. Winton

The horned lizard’s (or horned “toad’s”) remarkable habit of
ejecting blood from its eye when attacked, although well

authenticated, is so rarely observed that it is thought by many
to have its origin and its creditability in the little animal’s
dragon-like appearance. Even Ditmars confesses that it took an
actual demonstration, witnessed only after handling several hun-

dred specimens, to upset his skepticism. His description of the
performance is well known.

An Examination of 
Blood-ejecting Horned Lizards5

W.M. Winton

Mountain Short-horned Lizards (Phrynosoma hernandesi) can be found at elevations over 3000 m.

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4 Reprinted from Science, New Series, Vol. 40, No. 1026 (28 August
1914, pp. 311–312).

5 Reprinted from Science, New Series, Vol. 40, No. 1039 (27
November 1914, pp. 784–785).

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IGUANA  •  VOLUME 13, NUMBER 3  •  SEPTEMBER 2006 227HISTORICAL PERSPECTIVES

Hay (1892), Stejneger (1893), Van Denburg (1897), Bunner
(1907), Bryant (1911) and others have observed and mentioned
this peculiar habit. It is not limited to any single species. 

Various explanations have been suggested; among others
that the phenomenon is connected with the breeding season,
that it may be due to some parasite, and that it may be “a sec-
ondary use acquired by a relatively few forms.”

Bryant sectioned the eyelids of a blood-ejecting specimen,
and found them highly vascular and full of blood sinuses.

On July 4, while collecting specimens of Phrynosoma cor-
nutum for examination of stomach contents, I was fortunate

enough to witness this phenomenon. One of my students, walk-
ing by my side, stooped and thrust out his hand to pick up a
large specimen, when he was met by a sudden spurt of blood
coming unmistakably from the lizard’s eye. The blood spread
over the young man’s hand in a fan shaped and even smear,
extending from the second joint of the index finger to the wrist,
and being about thirty mm. wide at the base. On July 7, another
specimen, while being chloroformed, shot a quick jet of blood
from one eye. The blood was given an almost explosive impulse,
and formed a single thick drop on the inner wall of the bell jar.
On July 20, another specimen ejected blood while being anes-
thetized. In this case, the blood on the wall of the bell jar was
mixed with tiny fragments of skin and a few scales.

All three animals were subjected to a very careful examina-
tion. All were males. Their lengths were 108 mm., 110 mm. and
108 mm. The lizards were in good condition, even being free
from tapeworms and other intestinal parasites with which local
Phrynosomas are much infected. The stomach contents were
characteristic, consisting of agricultural ants, small beetles,
isopods, etc. In each case, the eye from which the blood was
ejected showed a small quantity of clotted blood in the posterior
corner. The vessels were slightly swollen. The cornea seemed to
be intact. In the first two cases there was a small spot in the scle-
rotic coat, which can be best described as a blood blister. The
contents on removal to a slide, and staining with Wright’s stain,
showed nothing except a few red corpuscles and lymphocytes.
The third specimen slowed nothing but a mass of clotted blood
in the posterior corner of the eye. In each case, careful dissec-
tions were made, using needles and working under a 48 mm.
objective. No parasites of any kind were found.

In my opinion, the most significant fact of all is that all
three animals were moulting, the third being in quite an
advanced stage.

Texas Horned Lizards (Phrynosoma cornutum) share with all other Horned Lizards the capacity to eject blood from sinuses near the eyes. This
appears to deter at least some potential predators.

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Texas Horned Lizards (Phrynosoma cornutum) have a broad distribu-
tion, but have been extirpated from some core areas by urban expan-
sion and alterations of habitat for agricultural purposes.

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228 IGUANA  •  VOLUME 13, NUMBER 3  •  SEPTEMBER 2006 HISTORICAL PERSPECTIVES

Random examinations of stomach contents, made by various
workers during the past forty years, have indicated that

Phrynosoma cornutum, the Texas horned lizard, is of great eco-
nomic importance. To determine its status as a valuable animal,
an examination of four hundred and eighty-five stomachs has
been made. As only a small per cent. of the animals found in the
field were captured and killed, several facts — besides the prin-
cipal one — concerning this animal have been disclosed.

The Texas horned lizard, unlike the other species of the
genus, is distinctly not a desert form. Its area of distribution is
quite extensive, going northward into Kansas, southward far into
the Mexican table land, and westward into Arizona; but, clearly,
the area of its greatest abundance is the north and south strip of
Texas known as the Black and Grand prairies. This strip of coun-
try includes the cities of Fort Worth, Dallas, Waco, Austin and
San Antonio — in fact all of the large cities of the state except
Houston and Galveston; and is preeminently the best part from
an agricultural standpoint. Within this area, where conditions are
all favorable, the Phrynosoma population averages at least thirty

to the acre. This is despite the fact that for a number of years
these lizards have been captured and sold to visitors from the east.

The life history has not been well worked out, but the
newly hatched young begin to appear by the first of August; so
that it is safe to say that the ordinary agricultural operations such
as spring and fall plowing, do not interfere with the life cycle.
The natural enemies are few and unimportant, being mainly
road runners and opossums.

The stomachs examined included the following forms:
four species of ants; four species of bees (mainly miner bees);
eight species of beetles; three species of stink bugs; nymphs of
grasshoppers and allied Orthoptera; five species of flies; and a
few caterpillars, some of which have not yet been identified.
The noxious forms found overwhelmingly outnumbered the
useful forms.

A Preliminary Note on the 
Food Habits and Distribution 
of the Texas Horned Lizards6

W.M. Winton

Texas Horned Lizards (Phrynosoma cornutum) often have been described as “ant specialists,” because of their habit of sitting near ant trails and pick-
ing off individuals that stray too close. Although consumption of small prey, if sufficiently abundant and easy to capture, can be energetically effi-
cient, Horned Lizards opportunistically eat essentially any small arthropod that will fit in their mouths.

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6 Reprinted from Science, New Series, Vol. 41, No. 1065 (28 May
1915, pp. 797–798).

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IGUANA  •  VOLUME 13, NUMBER 3  •  SEPTEMBER 2006 229HISTORICAL PERSPECTIVES

Agricultural ants were found in 80 per cent. and stink
bugs in 60 per cent. of the stomachs. Neither of these is much
subject to the attacks of birds. Obviously this enhances the
value of Phrynosoma. Incidentally, there was a remarkable con-
sistency or homogeneity in the contents of the individual
stomachs. For example, in one case, nearly all of the forms
present would be Hymenoptera; in another, nearly all would
be Heteroptera, etc. This could mean that individuals acquire

a taste for sour food, or fatty food, etc.; or, what is more likely,
that the same individual requires from time to time certain
special elements in its food.

From the data thus far assembled, it can be safely affirmed
that the horned lizards of Texas are of tremendous importance
to agriculture in that region; and may, perhaps, play as impor-
tant a part as does the common toad in the better watered
regions of the United States.

The Urine of the Horned Lizard7

A.O. Weese

Vauquelin,8 in reporting the first analysis of reptilian urine,
in 1822, stated that is was composed almost entirely of uric

acid, and since that time this fact has been interpreted by vari-
ous observers as an adaptation to the conditions of life in arid
regions, where animals obtain their only external water supply
in very limited quantities in the food substances, and this type
of nitrogenous excretion involves practically no water loss. The
reptiles of arid regions have been known for some time to excrete
practically all of their waste nitrogen in the form of uric acid and
its salts, while, on the other hand, birds and aquatic and semi-
aquatic reptiles may secrete considerable amounts of urea.

The urine of the horned lizard is excreted in the dry form at
the same time as the feces, from which it is separated by a con-
striction of the common mass, the material voided at any one time

having roughly the shape of a dumbbell, one of the enlargements
being composed of urine and the other of fecal matter. The fol-
lowing figures for the composition of the urine of Phrynosoma cor-
nutum (specimens obtained at Alamogordo, N.M.) have been
obtained recently in the laboratory of physiological chemistry of
the University of Illinois, the work having been undertaken at the
suggestion and under the direction of Dr. H.B. Lewis.

Constituents Mg. per Gm. of Dry Urine
Total nitrogen 260
Urea + ammonia nitrogen 1.4
Ammonia nitrogen 1.4
Uric acid 765
Creatinine Trace
Ash 87.5
Phosphorus as P2O5 3.5

It will be noticed from the above figures that uric acid
accounts for practically the total amount of nitrogen present, and
that there is no urea. The small amount of ammonia is probably
present as ammonium urate. The ash present is mostly composed
of foreign materials (sand grains, etc.) inseparable from the uri-
nary mass and therefore weighed and analyzed with it.

7 Reprinted from Science, New Series, Vol. 46, No. 1195 (23
November 1917, pp. 517–518).

8 Vauquelin, Louis Nicolas, “Examen des excrémens des serpens que
l’on fait voir en ce moment à Paris, Rue Saint-Nicaise,” Annales de
Chimie et de Phisique, 2me Serie, Tome 21, p. 440, 1822. Two boas,
species not stated, were the source of the urine examined in this case.
Uric acid had also been associated with reptiles as early as 1793, when
a “pasty deposit” found in the bladder of a tortoise by Vicq-d’Azyr
was found to contain this substance [footnote from original].

Like most congeners, Desert Horned Lizards (Phrynosoma platyrhinos) are found in arid regions that have at least some loose soil available for burrowing.

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