Fecal defense: Thi s beetle uses 'overhead sewer system' to ward off (most) predators,
Cornell biologists di scover
HOLD FOR RE LEASE: March 24, 2000
Cont act: Roger Segelken
Office: (607) 255-9736
ITHA CA, N.Y. -- Like eccentric street people
who deter muggers by acting crazily, one crafty
beetle has developed an equally outrageous
defense: Larvae of the tortoise beetle species
Hemisphaerota cyanea cover themselves with
their own feces, persuading most predators to
pass them by, Cornell University biologists
But at least one kind of one predat or is not
repulsed by beetle feces, Thomas Eisner and
Maria Eisner report in the Marc h 14 issue of
Proceedings of the National Academy of
Sciences (Vol. 97, pp. 2632-2646). The reason
for the breakdown in a nearly perfect de fense
Hidden inside a thatch of its own feces, the
remains a mystery.
larval tortoise beetle (Hemisphaerota cyanea
"You could call this the ultimate in recycling,"
) is safe from almost all predators. But
says Thomas Eisner, Cornell's Jacob Gould
research at Cornell Universi ty found one
Schurman Professor of Chemical Ecology,
predator, the carabid beetle (Calldida
describing the golden strands of feces
viridipennis), capable of penetrating the fecal
extruded from the beetle's hindgut and
defense shield. Photo by Thomas
fashioned into a thatched shield for its
otherwise vulnerable body. "Instead of leaving
excrement lying around, as most larvae do, this species has developed an overhead sewer
system. The thatch grows as the larvae metamorphoses, and for some reason that we don't
understand, the fecal shield deters most predators that would gladly eat the naked larva. They
won't even try. Maybe they're disgusted by the whole idea."
Then along comes a carabid beetle (Calleida viridipennis), quickly disassembling the thatch
shields and feeding on the hapless inhabitants.
The adult H. cyanea is a familiar sight on
palmetto fronds of Archbold Biological Station,
in the dry scrubland of cent ral Florida where
the professor and his wife, a senior res earch
associate in Cornell's Department of
Neurobiology and Behavior, conduct research.
Called a tortoise beetle becaus e of its turtle-
like shape, the iridescent blue adult insect
chews trenches through palmetto leaves as it
Until the Eisners looked closer, however, most
casual observers figured the small, golden bits
of stuff on palmetto fronds were lifeless. The
Fecal thatch produced by larval spots seemed never to move, and they did not
Hemisphaerota cyanea beetles deters most resemble any insect larva known to science.
predators - except the adult carabid beetle, Inside the Archbold laboratory and under the
shown here dethatching its next meal. Photo microscope, the defensive strategy was
by Thomas Eisner/Cornell University. revealed: Just minutes after hatching from the
egg, the H. cyanea larva begins feeding and
the first fecal strand emerges from a flexible turret on its abdomen. The first strands are short, but
they don't go to waste. Instead, the strands are shaped int o curves by the anal turret and they are
attached - by a droplet of glue from the turret - to a structure called a caudal fork that rises from
the larva's back.
Subsequent fecal strands from the voracious, leaf-eating larvae are longer and coiled. Depending
on whether the anal turret alternately flexes to the right or to the left, the strands are fashioned to
curve around either the right or left side of the larva, the biologists report in the journal. As the
immature insects molt and advance to another stage (called an instar) of their larval lives, the
caudal fork grows additional sections, and the dome-s haped fecal thatch grows ever more
If some fecal strands are damaged or lost - as happened when the biologists experimentally
removed some - the insect detects their absence and repairs the shield with new strands. Only
when a larva is about to pupate int o adulthood does the thatch-building stop.
Eager to learn the function of the thatch, the biologists devise d a taste test for two kinds of
potential predators, coccinellid beetle larvae and pent atomid bugs, which are commonly called
stink bugs. H. cyanea larvae with their thatch shields intact were uniformly ignored. "They did not
attempt to bite the thatch, or to force
themselves into it," the biologists reported.
Larvae denuded of their thatch were eaten
without hesitation. The biologists report that
one stink bug they watched "located first one
denuded larva then the other, and at e each by
impaling it on the proboscis and sucking it dry."
The Cornell biologists had determined the
function of the fecal thatch - defense against
predators - but also not ed that the covering
might protect the larvae from desiccation by
retaining moisture and blocking the sun.
That insight did not reveal why predators are
repulsed by the fecal thatch, however. The
thatch appears to be chemically inert,
A scienti st's forceps reveals the larval
according to Thomas Eisner, who has made a
tortoi se beetle (Hemisphaerota cyanea )
specialty of explaining the chemical defenses
inside an almost perfect defense structure, a
that organisms use to save themselves from
shield made of its own feces. Photo by
harm. Predat ory insects that touched the fecal
Thomas Eisner/Cornell University.
shield did not try to clean themselves, as do
most creatures that contact noxious chemicals. Perhaps it is because the thatch material - dried,
odorless feces - is inert that it succeeds at cloaking the living things inside, Eisner speculated.
The mystery deepened further when the biologists found one predator that disregards the beetle's
fecal shield. The carabid beetle C. viridipennis is so good at circumventing the shield - either by
forcing itself under the thatch or chewing through - that the biologists suspect the insect evolved
to specialize in tortoise beetle larvae. All that's left after a carabid beetle attack is the tortoise
beetle's turret - and the thatch that worked so well in deterring most predators.
"So fecal thatch is not really the last word in defenses or even in recycling," Eisner commented.
"That's all right. Predators have to eat, too. And every time we see a defensive strategy that
seems to work perfectly - until it fails - we learn something more about how living organisms
The study of tortoise beetle defenses was supported, in part, by a grant from the National
Institutes of Health.
The blue tortoi se beetle spends its entire life on the leaves of either a scrub or saw palmetto.
With its tiny jaws, it scrapes away at the palmetto leaf, leaving a thin yellowish line behind it as it
moves along the leaf. When alarmed, the blue tort oise beetle clamps itself down on the leaf
holding on with its yellow feet. Each foot is covered with hundreds of oily hairs, whic h stick to the
wax that covers the palmetto leaf. The larva of the blue tortoise beetle also feeds on palmetto
leaves. It covers itself with curved bits of waste material so that it looks like a tiny, upside down
bird's nest. This beetle is never common enough to damage a palmetto plant.
A TORTOIS E BEETLE
(HEMIS PHAEROTA CYANEA (SAY),
ON PALMS IN TEX AS
R. E. Woodruff
Florida Dept. Agric.
Div. Plant Industry
Circular No. 55, 1965
by Ba stiaan M. Drees,
Associate Professor of Entomology
and Extension Specialist
Hemisphaerota cyanea (say ) is a common, dark blue tort oise beetle that occurs along the coastal
regions of Texas that occasionally causes minor damage to various palms.
Adult beetles are about 3/16 inch long, gun-metal blue
to purple in color, and resemble a tortoise in shape
and compactness (Fig. 1). The elytra or wing covers
are deeply pitted with convex ridges between the pits.
The antennae are yellow except the black basal
segment. The head is often nearly concealed beneath
the pronotum. The larvae are yellowish to whit e grubs
with lateral abdominal projections. Each larva forms a
case from strands of fecal material in which it is
camouflaged. The abdomen is fitted wit h a structure
called a fecal fork which holds the case in position.
The case is composed of strands of fecal material
arranged in a circular fashion resembling plant fibers.
The life history of this insect has not been investigated thoroughly. Adults and larvae feed on
palm foliage, and pupation occurs within the larval case. Adults have been found in every month
of the year in Florida.
This species is apparently restricted to species of palms, both native and exotic. It has been
recorded from Acoelorrhaphe wrightii (Griseb. & Wendl.) Wendl. Ex Beccari, Arecastrum
romanzoffianum (Cham. ) Becc., Chamaerops humilis L., Cocos nucifera L., Sabal etonia Swingle,
Sabal minor (Jac q.) Pers., Sabal palmetto (Walt.) Lodd., Serenoa repens (Bartram Small), and
Washingtonia robusta Wendl.
Although not reported as a serious pest, the adults and larvae produce feeding scars on the
leaves They have been found in largest numbers on the native Sabal palmetto and Serenoa
repens in Florida. In Texas, they have been predominantly found on Washingtonia robusta
This species is known only from Georgia, Florida and Coastal Texas counties although it might
occur in other Gulf States where palms are found. It has been reported from Kentucky but
probably in error since no palms grow there.
Although no insecticide is specifically registered for the control of this species, this species shou ld
respond to products registered for the control of leaf beetles on palms.
Barber, H. S 1916. A review of the nort h american tort oise beetles. Proc. Ent. Soc. Washington
Blackwelder, R. E. 1946. Checklist of the cole opterous insects of Mexico, Central America, the
West Indies and South America. U.S. Nat'l Mus. Bull. 185(4):734.
Blatchley, W.S. 1924. The Chrysomelidae of Florida Ent. 8(3 & 4):39 -46.
Boving, a. G., & F. C. Craighead. 1931. An illustrated synopsis of t he principal larvae forms of the
order coleoptera. Brooklyn Ent. Soc., Brooklyn, N. Y., 351 P.; 125 Pl.
Jackman, J.A. 1976. A tortoise beetle, Hemisphaerota cyanea, on palms in Tex as. Southwestern
Say, Thomas. 1823. Descriptions of coleopterous insects collected in the late expedition to the
rocky mountains, performed by order of Mr. Calhoun, secretary of war, under the command of
Major Long. Jour. Cad. Nat. Sci. Philadelphia 3:435 -436.