Utah Lepidopterist

Volume 12 - No. 1, March 2005 (November, 2006 Update)

The Challenge of Raising Northern Utah Orange Tips 

By Todd L. Stout

Introduction

The purpose of this paper is to review strategies in order to facilitate the lab rearing of two Northern Utah orange tips   Anthocharis stella browningi (utah stella orange tip) and Anthocharis sara thoosa (southwestern orange tip.)   In order to review effective strategies to rearing these butterflies in the lab, it will be necessary to overcome certain obstacles as well as learn certain tips helpful in the field. There is little doubt that this group--the Anthocharis sara complex--is one of the more difficult groups of pierids to raise.

Obtaining Ova From Hostplants

Like other pierids, there are basically two ways of finding eggs.   The first method is to harvest ova off of their hostplants, and the second method involves collecting live females and setting them up in a cage to oviposit.  Both methods can be productive with the latter probably being the more productive.

Females of Anthocharis sara thoosa and Anthocharis stella browningi prefer to oviposit on the inflorescens and siliques of spotty montane mustards such as Arabis sparsiflora var. subvillosa (sicklepod rockcress,) Arabis perennans (pretty rockcress,) Arabis holboellii  (holboell's rockcress,) Arabis microphylla (little-leaf rock cress,) and Descurainia pinnata (pinnate tansymustard.)  In fact, any species of Arabis serves as a suitable lab hostplant for the Anthocharis sara complex.  

With regards to the oviposition preference on Arabis spp., unlike females of Pieris sisymbri nigravenosa (dark-veined spring white) and Pieris sisymbri sisymbri (spring white,) which prefer to lay their eggs in quantities of 1 to 7+ on the young basal leaves just above the overwintering basal rosette leaves, females of the  Anthocharis sara complex usually lay their eggs as singletons on the top of the plant.  (See pictures and graphics below.)

The only other Northern Utah pierid that utilizes the same oviposition strategy as Anthocharis on Arabis is Euchloe ausonides coloradensis (large marble.)  Because  Anthocharis stella browningi and Euchloe ausonides coloradensis are sympatric and synchronic in the Wasatch Range, there is a chance that if you find an orange ova on the tip of an Arabis plant that it will be either species.  At the same time, if you find an ova on top of an Arabis plant in the Basin and Range Province while looking for immatures of Anthocharis sara thoosa, you more than likely have found a thoosa since Euchloe ausonides coloradensis flies sparingly there.  

It is true that Euchloe (hyantis) lotta (desert marble) also uses Arabis spp. and Descurainia pinnata; but they tend to fly roughly two weeks after A. sara thoosa.  Therefore, the best time to find A. sara thoosa ova, depending upon elevation and other seasonal factors, is probably the fourth week of April whereas the best time to find desert marble ova is likely the first or second week of May.  

The other larval hostplant that Northern Utah Anthocharis uses is Descurainia pinnata.  Similar to Arabis spp., female Anthocharis sara thoosa and Anthocharis stella browningi will oviposit towards the upper part of the plant on the upper leaflets or on flower heads (assuming flowerheads are available.)   Again, if you contrast orange tips to spring whites, females of Pieris sisymbri sisymbri and Pieris sisymbri nigravenosa tend to oviposit towards the bottom leaflets of the plant.  

However, sometimes the distinction of oviposition preference between spring whites and orange tips is not so cut and dry with Descurainia pinnata as it is with Arabis.   On pinnate tansymustard, sometimes you might find an orange pierid ova on leaflets right in the middle of the plant where they could be either P. sisymbri or A. sara/A. stella.   A tip that might help here, is that P. sisymbri ova tend to be more elongate than those of the A. sara complex (and there usually are more of them on a plant.)   But, this difference can be quite subtle to the naked eye.

Another field tip that might be helpful in distinguishing orange tip, marble, and spring white ova from each other is that newly laid ova of these species groups are of a different color--see graphic below.  For example, the color of a newly laid orange tip ova is white, whereas the color of a newly laid spring white, large marble, and desert marble is green, yellow and light bluish white, respectively.  (Note:  From the time of oviposition, it generally takes any of these ova about four days to hatch under room temperature lab conditions; five days in nature. )

Species Group	0-24 hours	1-3 days	4-5 days
A. sara complex
Pieris sisymbri
Euchloe ausonides
Euchloe hyantis

Graphic showing the change in general coloration of Utah Pierinae ova from oviposition to eclosion.  Usually around 24 hours before eclosing, orange ova become golden brown with a dark upper portion representing the head of the soon-to-hatch larva.  

Obtaining ova from Wild-collected Females

In spite of the complexity of locating ova of the A. sara complex out in the field, likely, the more productive way to accomplish this is to collect a few females in the wild and set up a cage with hostplant in order to induce oviposition.

Since females of the A. sara complex lay their eggs quite quickly in nature, it is advisable to collect a female that is relatively fresh.  Orange tip females seem to start flying about 5-7 days after the males have started their main flight.  In order to set up a oviposition cage, please see instructions in the pictures below.

Regardless of the method, once eggs have been harvested, it is absolutely critical that they be separated from each other and placed individually into small containers such as solo cups for a few days until they hatch.  The reason for this is that first instar orange tip larvae (as well as most all other Pierinae larvae) are highly cannibalistic and will feed on other ova if it finds them.  Once newly hatched first instar larvae are gently placed onto the hostplant at a reasonable distance from the next larva on another flowerhead, one's concerns with cannibalism should be alleviated.

Always remember to check your solo cups for hatched ova regularly.

Recently-hatched first instar larvae should be gently placed on a flower head of Arabis spp. such as A. sparsiflora (left) or Descurainia pinnata (right.)  Most of the time, first instar larvae will burrow into the flower head for a day or so; after which it will crawl down the plant a short distance to find a silique to feed on.  When using pinnate tansymustard, if Anthocharis new hatchlings can't find flowers, they will, somewhat reluctantly, start feeding on the leaflets.

In order to obtain ova from wild-collected females, consider a setup like above where plant stalks are placed inside a cage adjacent to the side receiving sunlight.  (Venetian blinds are helpful in filtering direct sunlight.)  Place wild-collected females inside the cage.   Anthocharis females also use Arabis as a nectar source and can stay fed on the same plant while laying eggs.  (This picture shows A. cethura pima females ovipositing on Caulanthus lasiophyllum var. utahensis.)

 Setting up your rearing apparatus

Experience has shown that the open aquarium method, with a screen top, is an effective strategy for rearing all Utah Pierinae including orange tips.  The idea behind the open aquarium method is that the top is composed of a screen lid so that the setup has free air flow allowing caterpillar frass to dry.  Like caterpillars of the P. indra complex, Utah pierid larvae can get sick if overexposed to its own undried frass in a high humid microenvironment.   It's simply a situation that they're not accustomed to under natural conditions.  

At the same time, using a closed container method for rearing larger caterpillars is only advisable if one is willing to replace the hostplant daily as well as remove frass two to three times a day.  The only situation where using a closed container method might be recommended is if you are only raising one or two caterpillars, or if you're separating out mature larvae that are close to pupation. 

If setup correctly, the open aquarium method for pierids should last for about 6-7 days before the hostplant needs to be replaced.  In order to prepare hostplant to be placed inside a water bottle similar to what is shown in the picture above, it is best to prune the bottom portion of your mustard stalk as well as remove the lower one third to one half of all basal leaves.  This is advisable because the lower basal leaves, after a few days, are always the first to turn yellow making them unusable.   

The idea behind the open aquarium method is that the top is composed of screen so that the setup has free air flow allowing caterpillar frass to dry.   A single 10 gallon terrarium setup should be fine.  This particular setup consists of two 10 gallon terrariums taped together (the bottom glass hammered out of one) in order to accommodate taller growing larval foodplants. Mature larvae crawl off of the plant onto the paper towel in order to pupate.

"The Open Tub Method" Since Anthocharis larvae do not generally wander off the plant while feeding, using this setup works for rearing quite a few A. stella browningi larvae.  (Since this tub was not being used for normal purposes anyway.)   However, it is necessary to remove mature 5th instar larvae to an open aquarium setup or a closed container setup so that they can't escape as they tend to wander before they pupate.  (See left photo.)

Selecting the proper mustard to feed orange tip caterpillars

The key to the successful rearing of orange tip larvae to adults is to only feed them on the Northern Utah natural native mustards already mentioned.  Period.  If you understand that, the next few paragraphs, for all intents and purposes, are moot. 

In terms of larval hostplant preference, Northern Utah orange tips are not the generalists that their marble and white relatives mentioned above are.  For example, in addition to rockcresses and tansymustard, larvae of Pieris sisymbri, Euchloe hyantis, and Euchloe ausonides will also readily accept (as well as use in nature) other common valley floor and montane mustards such as Isatis tinctoria (dyar's woad,)  Streptanthus cordatus (heartleaf twistflower,) and Sisymbrium altissimum (tumble mustard) whereas orange tip larvae perish using these mustards under lab conditions*.   This gives those who wish to raise these aforementioned whites and marbles a much easier task in finding suitable lab hostplant than those wishing to raise orange tips.  

A deceptive obstacle for individuals who have not reared Northern Utah orange tips, is the fact that first instar orange tip larvae normally will gladly accept and initiate feeding on common mustards such as Cardaria draba (white top,) Chorispora tenella (blue mustard,) Brassica nigra (black mustard,) as well as the previously mentioned dyar's woad and tumble mustard.  Not only will they start feeding on these mustards, but they will appear to thrive on them until they reach fourth or fifth instars where they will suddenly perish probably due to slow poison or some other chemical imbalance.

The worst deceptive obstacle in raising Northern Utah Anthocharis, is confusing the alien, invasive, poisonous and unfortunately-common flixweed (Descurainia sophia) with its less-common, localized, montane relative Descurainia pinnata (pinnate tansymustard.)   To make matters worse, finding pinnate tansymustard, which is the suitable lab hostplant, requires a challenge as the plant seeks shady refuge under Juniper and other canyon trees.    In Northern Utah, pinnate tansymustard, is more common during springs resulting from very wet winters.   (On the positive side, pinnate tansymustard is an annual which usually grows in clumps allowing for harvesting of more than one sprig of plant for lab rearing.  One should not harvest the plant until it shows flowers and/or siliques [seed pods] for the caterpillars to feed upon.)

Again, the problem with flixweed, which superficially looks similar to pinnate tansymustard, is that it is extremely common in Northern Utah's valley floors as it grows in disturbed areas, adjacent to freeway off ramps, and even in your yard.  Unlike other yellow junk mustards, which orange tip larvae initially accept and inevitably die on, flixweed will kill orange tip larvae relatively quickly.  (Nevertheless, for some reason, instead of refusing this poisonous plant, orange tip larvae, like other yellow mustards, will feed on this plant.)  It is likely the most poisonous mustard for not only orange tip larvae; but other pierid larvae as well.  Do not use it!!

Outside of habitat preference, a key way of separating D. pinnata from D. sophia is by looking closely at the siliques.  On D. sophia, the silique is generally only slightly thicker than the stem it is attached to.  Also, this same silique is usually about three times longer than this same stem with which it is attached.  

On the other hand, with D. pinnata, the silique is usually to 2-3 times thicker than the stem it is attached to; yet is also approximately the same length as its accompanying stem.  In other words, D. pinnata siliques are stouter and shorter than those of D. sophia.

Third instar larva of A. sara thoosa camouflaging itself as if it were a silique on Arabis sparsiflora var. "subvillosa."	Anthocharis sara thoosa fifth instar on common Southern Utah hostplant Streptanthella longirostris (Photo courtesy Jack L. Harry)

Finding enough proper mustard to push orange tip caterpillars through to pupae

In a nutshell, one of the biggest challenges in raising these Northern Utah orange tips is the task of finding sufficient quantity of viable hostplant to raise them through to pupae in the lab.  

Just as finding pinnate tansymustard growing in the wild can sometimes be a challenge to the less-experienced lepidopterist, finding enough rockcress (Arabis spp.,) can be just as, if not more difficult.   In Northern Utah, Arabis perennans, is one of the more common rockcresses.   It can be found growing in spots along rocky outcroppings of our Northern Utah Canyons.  Another rockcress, which grows in rocky and slate formations of Northern Utah Canyons, such as Big Cottonwood Canyon above 5000', is Arabis microphylla (little-leaf rock cress.)  Although this plant can be quite short and provide less food bulk per stalk, many individual plants can contain dozens of stalks that can be used for lab rearing.

Probably one of the more frustrating rockcresses to rely upon for rearing purposes is Arabis sparsiflora var. subvillosa (sicklepod rockcress.) Although this plant is considered a perennial, basal rosettes of this variety of rockcress only live for a few years. This can be frustrating as you hike diligently to find a few good spots where this mustard is growing one year only to find that most of it is gone and growing elsewhere another year.

A helpful tip in finding more rockcresses for lab rearing is that Arabis sparsiflora var. subvillosa and Arabis perennans do tend to grow more abundantly at higher elevations.  Since colonies of Anthocharis stella browningi fly later at these higher elevations, it may be more prudent to raise browningi in May or June as opposed to April when Arabis is more plentiful.  In Northern Utah, some good locations to find Arabis growing more plentifully at higher elevations is along Skyline Drive to Bountiful Peak as well as at Farmington Canyon past Sunset Campground.

Another tip to remember as you harvest hostplant from the wild, is that, because Pieris sisymbri females lay multiple ova on   Descurainia pinnata and Arabis spp., as you cut and bag these plants, you likely will be bringing home some small, unnoticeable spring white eggs and/or caterpillars that are there just for the ride.  As you use this same hostplant and change it out about a week or so later, you will probably find these darker caterpillars feeding with your orange tip caterpillars. Therefore, whether you planned it or not, you may be raising a batch of Pieris sisymbri with your Anthocharis.  If you intend to push these spring white larvae through, it will then be necessary to take good field notes of when and where you harvested your hostplant in order to have accurate data for your Pieris sisymbri.  (This potential nuisance just seems to be part of the price you pay for rearing Northern Utah Anthocharis.)

With regards to harvesting hostplants from the wild, remember that rockcresses are perennials sending up spring stalks year after year from the same taproots.  Therefore, it is wholly inappropriate as well as pointless to destroy them by pulling them up by the roots.  All that one need do is prune the plant above the basal leaves taking some stalks and leaving others.    Experience has shown that by leaving some stalks in tact, the plant has a better chance of surviving.   

The same precaution need not apply to Descurainia pinnata since they are annuals coming up from seed.  If one wants to make sure and conserve colonies of these mustards, it might be fruitful to make sure and leave some plants untouched; so that, when the plant goes to seed, it can produce more in the future.

Finding Caterpillars in the Wild 

Although finding ova is not particularly difficult, it seems that finding late instar larvae is.  This difficulty of finding larger caterpillars is probably caused by several factors including larval parasitism, predation, as well as competition with larvae of Pieris sisymbri.  (For some reason, almost exclusively, if you find an older pierid larva on rockcresses or pinnate tansymustard, you will invariably be finding a spring white larva.)

Another possible explanation for the author's difficulty in finding late instar orange tip larvae is that he has spent most of his time searching plants of Arabis sparsiflora var. subvillosa growing in canyon bottoms in association with scrub oak as opposed to hiking the steeper rock faces where A. sparsiflora and A. perennans grow more consistently.  It is possible that the mortality rate of Anthocharis immatures is much less in those more protected areas.

Extended Pupal Diapause

One thing to remember when rearing Northern Utah Anthocharis is that pupae may not necessarily emerge the next spring. In the Western U.S., some groups of overwintering papilionid and pierid pupae are especially sensitive to the aridity of the region from which they fly. This sensitivity can extend their pupal diapause a certain number of years proportional to the overall dryness of the region–even if pupae are exposed to ideal conditions of humidity. (This innate self-protection defense mechanism helps protect against population crashes.)

This is scenario is applicable to Northern Utah Anthocharis stella browningi and Anthocharis sara thoosa in differing magnitudes. Because of the significance of the average yearly rainfall in the Wasatch Mountains, pupae of A. s. browningi generally emerge after one to two winters of diapause--depending upon lab conditions. At the same time, because of the more arid nature of the Basin and Range Province, pupae of A. s. thoosa generally emerge after two to four winters of diapause. Within a certain margin of error, these same timeframes also apply to the other marble and checkered white species that fly in these same regions. Like A. s. browningi in the Wasatch Range, pupae of E. ausonides and P. s. sisymbri generally take 1-2 years to emerge whereas like A. s. thoosa in the Basin and Range Province, pupae of E. h. lotta and P. s. nigravenosa generally take 2-4 years to emerge.

Even more extreme examples of this general phenomenon are evident when comparing average lab emergence times of Mojave Desert populations of Anthocharis cethura pima (3-9 years) with Southern Ohio colonies of Anthocharis midea annickae (one year.) (That probably tells you how arid the Ohio desert is.)

Pupae and female emergee of Anthocharis sara thoosa taken from the Oquirrh Mts. behind Cedar Fort, Utah County, Utah.  The time frame between finding ova and emergence of adult was nearly three years.

*  Author's Update:  (27 Apr 2006)  During the spring of 2005, a utah stella orangetip (Anthocharis stella browningi) larva was raised from ova to to pupa utilizing dyar's woad (Isatis tinctoria).  Although this pupa did not emerge during the spring of 2006, it is still alive.  This plant may yet be proven as a viable lab host for some species in the A. sara complex.  25 Nov 2006 Update:  During May, 2006, several dozen Anthocharis stella browningi immatures as well as Anthocharis stella nr. stella and Anthocharis sara immatures from SW Oregon were successfully reared to pupa on dyar's woad (Isatis tinctoria). 

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