|PERSONAL BIBLIOGRAPHY REPRODUCTIONS--THIRTYONE
37. KRULIK, GERALD, "Spiders That Like Bromeliads/Bromeliads That Like
Spiders", PUP TALK (Saddleback Valley Bromeliad Society), 14(1) p.5-8, January,
Spiders That Like Bromeliads/Bromeliads That Like Spiders WAS REPRINTED IN IILAWARA
BROMELIAD SOCIETY NEWSLETTER QUARTERLY, SYDNEY, AUSTRALIA.
By Jerry Krulik
Which of the above commments is more true? Actually, they are both equally true, since I will write
about an example of a mutual symbiotic association. Two similar ways of life are parasitism and
commensalism. For example, a parasite takes from its host, giving nothing in return or even killing
its host. Examples might be tapeworms or the flu virus. A commensal association is one in which
one partner benefits, while the other partner does not benefit or at least is not harmed. Examples
would be bromeliads and orchids living on the bark of a tree; the epiphytes have a nice place to live,
without harming the tree.
Symbiosis is an association between organisms, in which both partners benefit. An example is the
sea anemone-clownfish association. The sea anemone keeps away predators with its stinging
tentacles, and the clown fish keeps it free of parasites. The spider-bromeliad relationship is a
symbiotic association. Both species benefit from this way of living. In fact, the spider prefers to live
only on certain species of bromeliads.
This is a strange relationship, to be sure. Spiders are carnivores. They don’t eat plants; they use
them to hold their webs, or to serve as their hunting ground. The biological literature is NOT filled
with examples of spiders being restricted to one or a few species of plants. In fact, this first article
described the first (but it turns out, not the only) bromeliad-spider love fest.
Many of the most common spiders are the web spiders. These spin their traps to catch their prey,
while waiting passively. I consider them to be almost the equivalent of predatory cows, needing
little intelligence to sit and wait. Another group is the tarantulas. These large spiders search out
prey, but are typically ambush predators (but more later on these). Another large group are the
jumping spiders or Salticidae (this comes from a Latin word meaning jumping, not salt). These
often brightly-colored spiders are the wolves of the spider kingdom, and some common types are
called wolf spiders and hunting spiders. They are active hunters, using their sight to focus on prey,
and their speed to catch them, like wolves.
I have watched many jumping spiders and find them intelligent and fascinating. Once in my Chicago
greenhouse, I noticed a common zebra-striped small jumping spider on top of a cactus. As I
worked, I saw a large fly lazily doing the rounds. As it came within a few inches of the cactus, I
watched the spider watching the fly—jumping spiders usually have 8 eyes, 4 in front, and the others
arranged to allow them to see in all directions at once! Suddenly the spider jumped into the air,
caught the fly, and dropped back on the cactus with its prey larger than itself. Another time I was
resting against a fence in Taiwan, waiting for some equipment to start. I watched a fair-sized
jumping spider with a metallic green pattern walking along the fence top. Suddenly a fly landed on
the horizontal fence beam, about 6 inches from the spider. It saw the fly and immediately stopped,
then moved slowly to the edge of the beam while the fly rested. I watched it carefully move out of
sight of the fly, then race down the beam exactly to where the fly was sitting, and immediately race
up and over the edge. Unfortunately, it missed the fly, but the intelligence and activity it showed was
startling in such a tiny animal.
The University of Kentucky has a good web page on these animals. (1) Most jumping spiders are
less than one inch long.
So, given that these spiders are such active hunters, why would they want to stick with some
bromeliad? When we think of bromeliads, most of us think of flowers and leaves. Both can be
beautiful and large, or sometimes small and insignificant. Fruits, except for pineapples, are not of
Occasionally we think on the next level, about how many bromeliads are tank plants, with water-
holding reservoirs in their leaf bases. This leads to thoughts of frogs, mosquitoes, water mites, and
other normal inhabitants of the water in those leaf bases.
If anyone goes even more deeply into things, usually it involves pests of bromeliads. Fortunately
bromeliads are pretty immune to most common garden pests, except sometimes mealy bug, scale,
and aphids. While many types of beetles attack the body of bromeliads in Central and South
America, none seem to have become established in cultivation here.
Some ecological researchers have now found that some types of jumping spiders like certain
bromeliads to the exclusion of other plants. One spider, Psecas chapoda, is pretty much restricted
to one species of bromeliad, Bromelia balansae. This is very unusual, to say the least. Very few
spiders are associated with any type of plant, unlike insects, since spiders are all carnivorous.
Plants usually figure only as a convenient support for webs or hiding and hunting places for
spiders. (2, 3)
Here is Psecas chapoda, with its pretty red abdomen with a white racing stripe. It looks built for
Bromelia balansae, above, looks like a cozy place to live. Left, close-up of central leaves (5); Right,
clump of plants (6).
But this looks like a classic case of the odd couple. What could the bromeliad and spider get from
each other? In the case of the bromeliad, it gets up to 40% of its nitrogen needs from the spider. The
scientists found that the remains of the prey and more importantly, the feces, fertilize the
bromeliad. The spiders in turn prefer to live in the dried leaves at the base of the plant, laying their
eggs there, raising their young, and returning from hunting trips in the surrounding area. The
spiders also prefer to live in B. balansae which grow in grasslands rather than in the forests, as
there are more prey in the grasslands. Older spiders preferred the outer layers of dry leaves, while
most of the babies and females with egg sacs lived close to the center of the dried leaves. This
gives the young protection from drying out, and allows them to disperse and hide from each other
to prevent cannibalism. (7, 8) This symbiotic relationship does seem to work. In a one year field
experiment, the plants with spiders had leaves 15% longer than the plants which had the spiders
removed. And when three quarters of the dried leaves are taken off, the spiders leave the plants.
Curiously, they also desert the plants once they start to elongate and flower. (9)
Evidently this discovery of commensalism set off a frenzy of new biological research. Soon more
examples were found. (2) A new species of jumping spider, Eustiromastix nativo, was collected
during inventories of spiders in campos nativos and in restingas, sandy dry areas with low
scattered vegetation. These new spiders only occurred on Vriesia neoglutinosa (10), below left, and
on Aechmea blanchetiana, below right (11).
The spider itself is described as having a black body with a triangular white patch. I could not find a
color photo, just the dissected out genitalia. Here is a related species, E. obscuris. (12)
Further work showed that 9 species of jumping spiders were associated with up to 23 bromeliad
species in cerrados (savanna-like vegetation), semideciduous and seasonal forests, coastal sand
dune vegetation, restingas, inselbergs, highland forests, chacos, and rain forests at 47 localities in
Brazil, Paraguay, Bolivia, and Argentina. While some species were only found on one bromeliad,
others lived in up to 8 bromeliad species.
This brings us to another group of spiders, the Theraphosidae, or tarantulas. Would you believe that
there is a tarantula restricted to species of Aechmea and Hohenbergia bromeliads? (13) This is not
a small animal. Pachistopelma rufonigrum has a 6 cm (2.5 inch) body size, with a leg span of 15 cm
(6 inches)! (14). This is the adult animal, below (15), and a young one on Aechmea (13).
The scientists found that this large tarantula only lives in these two species of tank bromeliads, in a
white sandy dry desert area. They were unable to find these spiders anywhere except in the
bromeliads. Everything from eggs and babies, to the long lived adults, were found in the plants. They
hid deep within the plants in the daytime, but came out to hunt at night. The spider has lowered eyes
and a flattened body, to allow it to hide between the leaves. So far, no tests have been run to see
how each species actually benefits. The authors speculate that the spider receives protection
against high temperature and low humidity, and hiding places from their predators. I postulate that
they will find that these bromeliads benefit from the much more impressive dung and prey remains
from the tarantula, as compared to the small jumping spiders.
I eagerly await further studies and discoveries. Evidently arachnidologists have not been combing
bromeliads for unique spiders, but I am sure they will do so now. In the interim, when you re-pot,
please don't squash the spiders!
All photos are by others, as referenced below.
2. Gustavo Q. Romero, Biotropica, 38 (4), pp 522-530, Geographic Range, Habitats, and Host Plants
of Bromeliad-living Jumping Spiders (Salticidae)
3. Gustavo q. Romero and João Vasconcellos-Neto, J Anim Ecology, 74(1), pp 12-21, The Effects Of
Plant Structure On The Spatial And Microspatial Distribution Of A Bromeliad-Living Jumping Spider
4. Maddison, Wayne. 1995. Psecas. Version 01 January 1995 (under construction). http://tolweb.
org/Psecas/3062/1995.01.01 in The Tree of Life Web Project, http://tolweb.org/
7. Gustavo Quevedo Romero, João Vasconcellos-Neto, Journal of Arachnology 33(1), (April 2005),
pp. 124–134, Spatial Distribution And Microhabitat Preference Of Psecas Chapoda (Peckham &
Peckham) (Araneae, Salticidae)
8. Gustavo Quevedo Romero, Doctoral dissertation: Associações entre aranhas Salticidae e
Bromeliaceae : historia natural, distribuição espacial e mutualismos (Associations between
jumping spiders (Salticidae) and Bromeliaceae), Idioma: Português, Data de Publicação: 2005,
Local de Publicação: Campinas, SP , Orientador: João Vasconcellos Neto ,
Instituição: Universidade Estadual de Campinas . Instituto de Biologia Nível: Tese (doutorado)
9. Romero GQ, Mazzafera P, Vasconcellos-Neto J, Trivelin PC, Ecology. 2006 Apr; 87(4):803-8.
Bromeliad-Living Spiders Improve Host Plant Nutrition And Growth.
13. DIAS, Sidclay Calaça and BRESCOVIT, Antonio Domingos. Notes on the behavior of
Pachistopelma rufonigrum Pocock (Araneae, Theraphosidae, Aviculariinae). Rev. Bras. Zool.
[online]. 2003, vol. 20, no. 1 pp. 13-17. Available from: <. ISSN 0101-8175. doi: 10.1590/S0101-
81752003000100004&lng=en&nrm=iso>. ISSN 0101-8175. doi: 10.1590/S0101-81752003000100004.