Western Tiger Swallowtail (Papilio rutulus)

Western tiger Swallowtail (Papilio rutulus) nectaring on Purple Sage (Salvia leucophylla)

Nothing is more enchanting than
the appearance of large butterflies in our gardens. July is typically a busy
butterfly month, but we’ve been watching the Western Tiger Swallowtails since
spring.  If you live in the western
United States you may be enjoying them as well.   To learn more
about attracting butterflies to your garden see our June 2012 posting (http://mother-natures-backyard.blogspot.com/2012/06/butterfly-gardens.html
).

The Western Tiger Swallowtail
ranges through much of western North America from N. Dakota south to New Mexico;
west from British Columbia, Canada to Baja California, Mexico. The species is
similar to the Eastern Tiger Swallowtail (Papilio
glaucus) of eastern N. America and is found mostly between sea
level and 5000 ft. (1500 m.).  The tiger swallowtails were formerly included in the
genus Pterourus. 

Many westerners recognize this
butterfly on sight - it’s large, distinctively colored and relative common. While
actually at home in riparian woodlands and stream sides, it’s not unusual to
see these butterflies in gardens and city parks.  One thing is certain: you’re more likely to
see them in places that have food for their larva (caterpillars): Willows,
Cottonwoods, California
Sycamore (Platanus racemosa) and ash (Fraxinus spp.).  That’s why
we have so many Tiger Swallowtails in Mother Nature’s Backyard.

 

Two other swallowtail species visit western Los
Angeles county gardens (see above).  The
Giant Swallowtail is a large black butterfly with a prominent yellow triangle
on its open wings.  The Anise Swallowtail,
common in some neighborhoods,  looks like
a large yellow butterfly wearing a set of heavy black shoulder-pads with 3 short
yellow stripes.  The Pale Swallowtail,
which has similar markings to the western tiger swallowtail, is black and white
(rather than black and yellow) and is rare in gardens.

Western Tiger Swallowtails are large
butterflies.  Their wingspan can be as
much as 2 ¾ to 4 inches (7 to 10 cm), making them one of the largest
butterflies in many western gardens. Females are larger than males, but otherwise
similar in appearance.  They are brightly
colored, predominantly yellow and black, with spots of blue and red/orange.  The wings are striped like a tiger – four
black stripes on yellow - on both the upper and under surface.  The margins of both fore- and hind wings are
edged in black with yellow dashes.

 

Western Tiger Swallowtail (Papilio rutulus)

 

The
hind-wings have ‘tails’ reminiscent of the tail of a swallow – hence the common
name ‘Swallowtail’. The lower inner margins of the hind-wings have a dot of
blue and orange (some individuals may have additional blue spots, particularly
on the underside of wings). The
head and body (thorax and abdomen) are striped yellow and black. The
antennae are knobbed (not hooked) at the tip. You can get a good look/photo of
these butterflies as they sun or nectar, often with their wings spread.      More excellent photos are available  at: http://www.butterfliesandmoths.org/species/Papilio-rutulus
and http://nathistoc.bio.uci.edu/lepidopt/papilio/tiger.htm
.

 

While
limited to summer in colder climates,  Tiger
Swallowtails fly from January through September/October (even all year) in warm
S. California sites.  You may note that
spring-flying individuals are slightly smaller and paler than their summer
counterparts.  But they still are
distinctively Tiger Swallowtails.

 

It’s
not uncommon to see males patrolling back and forth through the garden, searching for receptive females.
 In
the wild, males congregate at shallow pools or damp ground to drink and obtain
dissolved minerals. This behavior (termed ‘puddling’) is not often observed in
gardens, in large part due to a lack of suitable damp ground.  Males also feed on carrion and dung.  And both male and female adults visit a wide range of flowers to obtain nectar
(food). 

 

Females lay eggs on the leaves of host plants
(plants that provide larval food).  The
eggs, which are shiny, round and deep green, are laid singly on the undersides
of leaves. A female produces approximately 100 eggs in her lifetime.   If you are fortunate, you may witness a
female laying eggs.  She curves her
abdomen down, releases a sticky egg and deposits it on the leaf. The tiny
caterpillar (larva) emerges 4-5 days later.  Ah, the miracle of life!

 

Tiger Swallowtail larvae go through five life
stages (instars) before they pupate (form a chrysalis or
cocoon).  They molt between each stage,
growing an entirely new exoskeleton to fit the growing, changing caterpillar.  During the early stages, when the larvae are
small, they look like a bird dropping – a deterrent to birds and others that
might want to eat them.  For pictures of
Western Tiger Swallowtail larvae see: http://butterfliesofamerica.com/papilio_rutulus_immatures.htm
and http://www.wildutah.us/html/butterflies_moths/papilionidae/h_b_papilio_rutulus_immatures.html

 

Later
stage instars are bright green with a pair of large eyespots, resembling eyes,
at the tail end.   This protective
coloring also serves to camouflage and fool  predators. 
The larvae also possess another potent weapon.  They can raise a brightly colored (and foul
smelling) forked organ called the osmeterium (‘stink horn’) from behind the head.
The sight and smell of a raised osmeterium are enough to frighten off many
potential predators.  

 

Tiger
Swallowtail larvae eat leaves, grow and poop – that’s what caterpillars
do!  The larval food plants vary somewhat
from place to place but always include willows (Salix species), Cottonwoods and Aspen (Populus species) and Ash (Fraxinus
species).  In California, additional native
plant sources include the California Sycamore (Platanus
racemosa), plants in the Cherry Family (Prunus
species), Birches (Betula species) and
Alders (Alnus species).  The larvae usually live high in trees and
shrubs and are seldom seen by humans.

 

Western Tiger
Swallowtails have 2-3 broods in warm coastal S. California (only one in colder
areas).  Summer larvae progress through
their development rapidly – sometimes as quickly as 15-20 days from egg to
butterfly. Summer broods tend to be the largest.  Late (fall) broods over-winter in the
chrysalis in many areas.  As an aid to
camouflage, the summer chrysalids are bright green while the fall/winter ones
are brown to blend in with surrounding wood.  
Butterflies emerge from the winter chrysalids from January through
spring, depending on the ambient temperature.

 

Western Tiger Swallowtail (Papilio rutulus) sunning on Lemonadeberry (Rhus integrifolia)

 

Watching butterflies in
the garden is a fascinating hobby.  It’s inexpensive,
you don’t have to travel and you can learn a great deal about the natural world.
You may even discover something new about insect behavior!  All you really need are patience and a
comfortable place to sit; a camera and binoculars are also useful tools. 

 

Here are some simple things
you can do to make a home for Western Tiger Swallowtails

1. Plant their favored plants. 

Adult (nectar) plants (relatively simple to provide)

·       
California native plants: California buckeye (Aesculus
californica); native dogbanes (Apocynum
species); native Milkweeds (Asclepias fascicularis; A. eriocarpa; A. speciosa); native
Milkvetches (Astragalus species); Cobwebby
thistle (Cirsium occidentale); Yerba Santa (Eriodictyon spp.);    Dunn’s Lobelia (Lobelia
dunnii  var. serrata); perennial Mints (Monardella
lanceolata ; M. linoides; M. macrantha; M.  villosa); Penstemons; Salvias
(especially Purple Sage, Salvia
leucophylla, in our garden); Wooly blue-curls (Trichostema lanatum)

·       
Other garden plants:   abelia, agastache, butterfly bush (Buddleia), lilac, lillies, mints, zinnia

Larval (host) plants (require a little planning)

·      
California native plants: cottonwoods,
poplars and willows are too big and invasive for most yards.  Try instead native White alder (Alnus rhombifolia), native Prunus species
like Hollyleaf & Catalina Island cherries (Prunus ilicifolia), Desert Peach (Prunus andersonii), Desert Almond (Prunus fasciculata), Desert Apricot (Prunus fremontii), native plums and Western chokecherry (Prunus virginiana var. demissa) and California ash (Fraxinus dipetala).

·       
Other garden plants: anything in Prunus
family (cherries; plums; peaches; nectarines; apricots)

2. Use
   pesticides sparingly – or not at all. 
   Practicing Integrated Pest
   Management (IPM) is a safer, greener approach to managing garden
   pests.  Keep plants healthy, use
   simple preventive measures and use chemical pesticides only as a last
   resort.   To protect pollinators, never apply pesticides to blooming
   plants.  For more see: http://www.xerces.org/pesticides/ 




3. Provide
   a source of water.  This
   doesn’t need to be large or sophisticated. 
   We use glazed clay saucers (like you put under pots) filled with
   garden soil, gravel and water.  You’ll
   need to add water daily in warm weather. 
   If you’re clever, you could probably adapt a hose-fed birdbath
   dripper to provide water during the day.




4. Provide
   sunny, safe places for sunning.  Butterflies need warm, safe places to
   perch and warm themselves.  Tiger
   Swallowtails prefer to perch on leaves - 
   most shrubs with medium to large leaves are fine.  The area should be sunny and out of wind
   if possible.




5. Encourage
   your neighbors to follow butterfly-friendly practices in their yards. 

 








Western Tiger Swallowtail (Papilio rutulus) nectaring on Purple Sage (Salvia leucophylla)

             ___________________________________  

We encourage your comments below.   If you have questions about Western Tiger
Swallowtail or other gardening topics you can e-mail us at :  mothernaturesbackyard10@gmail.com