Indian Walking Stick Integrated Pest Management

1. PEST NOTES Publication 74157
University of California
Statewide Integrated Pest Management Program
Agriculture and Natural Resources May 2011
Walking stick insects, order Phasmatodea, are mostly tropical insects that are considered an entomological curiosity because of their remarkable mimicry of twigs and leaves. Several species are popular in the pet trade and for grade school demonstrations and thus get moved extensively with some, such as the Indian walking stick insect, Carausius morosus, becoming established in many parts of the world. The Indian walking stick is native to southern India, but the precise time of its establishment in California is unknown; the first official finding occurred in San Diego County in 1991 and shortly thereafter in San Luis Obispo County. There has been an increase in homeowner reports of walking stick damage in the last 10 years along the Central and Southern coasts of the state.
The establishment of Indian walking sticks in California landscapes has occurred as a result of their escape from captivity or through discarding of eggs. Indian walking stick insects produce viable eggs without mating and broadcast them in their cages or containers; the eggs become co-mingled with their droppings (frass). The eggs are difficult to distinguish from frass and are easily tossed out in the process of cleaning the cage. Owners of walking stick pets must be responsible for understanding the biology of these organisms and caring for them properly, which includes bagging the cage debris and disposing of it in the trash.
IDENTIFICATION
The adult Indian walking stick is 2 3/4 to 4 inches long, wingless, and usually brownish with a long, thin body and legs (Fig. 1). It can retract its legs seamlessly alongside its body, enhancing the insect’s sticklike appearance; the forelegs project forward adding to the overall length of the insect.
Eggs of Indian walking sticks look like seeds. They are ovoid, grayish-brown with a small, buff-colored cap (operculum) on one end through which the young insect emerges (Fig. 2). The eggs are similar in size to the frass these insects produce, but the frass is rough in texture. There are five nymphal instars, each instar progressively larger with each molt. Nymphs are similarly colored to the eventual adult, and it is difficult to distinguish larger nymphs from adults.
A few walking stick species are native to California including the western shorthorned walking stick, Parabacillus hesperus, the gray walking stick, Pseudosermyle straminea, and species in the genus Timema. All of these species feed primarily on grasses and scrub brush—mostly woody shrubs—in dry wild areas and haven’t been reported as pests in landscapes. Adult females of the Indian walking stick can be readily distinguished from these species by the red markings at the base of their front legs (Fig. 3).
LIFE CYCLE
Adult females can live for several months and produce several hundred eggs during their lifetime. Eggs hatch in 10 to 12 weeks at room temperature. The five nymphal instars take 4 to 6 weeks to complete before the insect reaches adulthood. No rigorous studies of temperature-dependent developmental durations or reproduction have been published for this species. Most knowledge has been gained from their use in the pet trade.
Indian walking sticks feed on a wide variety of plant species in California including but not limited to azalea, bramble, camellia, geranium, hawthorn, hibiscus, ivy, jasmine, oak, privet, pyracantha, rose, and some common garden vegetables.
Integrated Pest Management for Home Gardeners and Landscape Professionals
Indian Walking Stick
Figure 1. Indian walking stick adult.
Figure 2. Indian walking stick egg (actual size about 1/10 inch); the cap, or operculum, is the opening through which the first- stage instar will emerge.
Figure 3. If an adult female Indian walking stick is in danger of being harmed, it will splay its forelegs to reveal a bright red patch on its inner femora near the attachment point to the body. This red marking distinguishes the Indian walking stick from native California species.

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Indian walking sticks reproduce
mainly asexually (parthenogenetically),
with females haphazardly dropping
eggs while they feed or rest. Males are
known but are rare; nothing is known
regarding the conditions required to
produce them. Females frequently feed
and move through foliage at night but
also can be observed feeding through-out
the day. The conditions along the
coast of California are mild enough
for these tropical species to survive
through the winter, although they do
so mainly in the egg stage. Thus, most
observations of activity and damage
take place during the spring when
nymphal stages emerge from over-win-tered
eggs and begin feeding. Multiple
generations occur through the summer
with nymphs and adults observed well
into November or until the first frost.
Stick insects exhibit crypsis, a combi-nation
of color, shape, and behavior
that makes them blend into the envi-ronment,
thus avoiding detection by
predators. When stick insects move
through the foliage, they typically
do so very slowly and with swaying
movements that mimic the effects of
wind on the plant. When disturbed,
the insect retracts its legs and remains
perfectly still, even when handled.
Only when aggressively handled will
the insects display yet another color
phenomenon—aposematic, or warning,
coloration. If the insect is in danger of
being harmed it will splay its forelegs
to reveal a bright red patch on its inner
femora near the attachment point to
the body (Fig. 3). This color can startle
predators, giving the insect a chance
to escape. When a stick insect isn’t on
a feeding site, such as walking on bare
ground or poised on a man-made struc-ture,
they become easily evident, and
due to their large size, can be alarming
to some people.
Indian walking stick egg survival
hasn’t been studied in California. The
eggs in their native home are attrac-tive
to grain-feeding ants that mistake
them for seeds and cart them back to
their nests but never feed on them.
Since the eggs are broadcast into the
environment, the ants play a role in the
egg’s survival by bringing them into
the nest, where they remain undis-turbed
until hatching.
DAMAGE
The worst damage typically is recorded
in the springtime when nymphs are
hatching from eggs and feeding on
new flush growth of many plants spe-cies
in landscape settings. They feed
aggressively on small-leafed varieties
of ivy and privet. Nymphs and adults
feed heavily on the margins of mature
leaves, creating a tattered appearance,
or fully consume smaller, tender leaves
(Fig. 4). Populations develop unnoticed
until significant feeding takes place.
Damage reports in landscapes have
been spotty and inconsistent from year
to year on the Southern and Central
coasts of California. The most frequent
complaints arise from residents when
they encounter walking sticks on win-dows,
doors, or even inside homes on
warm summer nights.
MANAGEMENT
Indian walking sticks usually are
mostly a nuisance in the landscape,
although in some years and in some
locations they can seriously defoliate
plants and cause damage to valued
specimens.
Prevention
Don’t release Indian walking sticks or
other exotic insects into landscapes or
wild areas. If you are keeping these
species as pets, when cleaning the cage
put the debris into a bag and close the
bag securely before throwing it in the
trash. Do not toss loose debris outside,
as it might contain eggs or the insects.
If you no longer care to raise Indian
walking sticks, place the entire contents
of the cage including live insects and
all debris into a plastic bag, tie the bag
securely and place it in a freezer for at
least 48 hours before throwing it in the
trash.
Biological Control
No biological agents have been released
for their control, and it is assumed that
generalist predators feed upon them
when encountered; no definitive stud-ies
have been conducted.
Mechanical Control
Removing and destroying the insects
can reduce populations over time and
reduce evidence of feeding; however,
finding them is difficult due to their
cryptic nature.
Chemical Control
There is no research on pesticide ef-ficacy
against walking sticks. Pesticide
applications aren’t recommended at
this time, as they might kill beneficial
insects occurring in the landscape.
Care must be taken when using insecti-cides,
especially when applications are
made to edible plants. v
Figure 4. Indian walking stick feeding
damage.

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AUTHORS: D. H. Headrick, Horticulture and
Crop Science, Calif. Polytechnic State Univ.,
San Luis Obispo, Calif. and C. A. Wilen, UC
Statewide IPM Program, San Diego Co.
TECHNICAL EDITOR: M. L. Flint
EDITOR: M. L. Fayard
ILLUSTRATIONS: Figs. 1–4, R. K. Perry.
Thanks to Judy Bell and Michael Bostwick of
the San Diego Zoo for providing plant lists.
This and other Pest Notes are available at
www.ipm.ucdavis.edu.
For more information, contact the University of
California Cooperative Extension office in your
county. See your telephone directory for addresses
and phone numbers, or visit http://ucanr.org/ce.cfm.
University of California
Agriculture and Natural Resources
Produced by UC Statewide
Integrated Pest Management Program
University of California, Davis, CA 95616
University of California scientists and other
qualified professionals have anonymously peer
reviewed this publication for technical accuracy. The
ANR Associate Editor for Urban Pest Management
managed this review process.
To simplify information, trade names of products
have been used. No endorsement of named products
is intended, nor is criticism implied of similar products
that are not mentioned.
This material is partially based upon work
supported by the Extension Service, U.S. Department
of Agriculture, under special project Section 3(d),
Integrated Pest Management.
WARNING ON THE USE OF CHEMICALS
Pesticides are poisonous. Always read and carefully follow all precautions and safety recommendations
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away from food or feeds, and out of the reach of children, unauthorized persons, pets, and livestock.
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Confine chemicals to the property being treated. Avoid drift onto neighboring properties, especially gardens
containing fruits or vegetables ready to be picked.
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the pesticide according to the label, or take unwanted pesticides to a Household Hazardous Waste Collection
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