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Contents:

1) Welcome!

2) Status of the Population

3) Degree Days and Monarchs

4) Good Years vs Poor Years

5) Raising Monarchs in the Summertime

6) Reminder: Order Your Tags Today!

7) 15% OFF Summer Reading Specials in Gulliver's Gift Shop!

8) CyberSurfari 2002

9) Adopt-a-Classroom

10) How to Unsubscribe from this Update

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1) Welcome to Monarch Watch's Update List!

You are receiving this email because you have provided Monarch Watch with your email address at some point and expressed interest in receiving updates from us. If you do not wish to receive these periodic (probably monthly) email updates or feel that you were subscribed in error, please see the unsubscribe information at the end of this message.

Have you somehow missed (or misplaced ;-) an update? Now you can find all of the updates archived online at

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If you know someone that you think might be interested in receiving these email updates from Monarch Watch with monarch news, special announcements, tips on raising monarchs in your classroom, monarch tagging information and a whole lot more, please send them on over to

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to join our new Monarch-Watch-Update email list - it's easy!

Monarch Watch (http://www.MonarchWatch.org) is a not-for-profit educational outreach program based at the University of Kansas. We run a Monarch tagging program and offer Monarch Rearing Kits, Monarch Tagging Kits, and other educational/promotional materials that allow you to actively experience the monarch life cycle and its spectacular fall migration.If you have any questions, please feel free to contact us anytime!

Your friends at Monarch Watch
http://www.MonarchWatch.org
monarch@ku.edu

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2) Status of the Population

by Chip Taylor

The first half of May was cold and rainy over much of the Midwest and these conditions certainly slowed the movement of first generation monarchs originating in the southern states, and Texas in particular, from moving into the northern states. However, reports over the last 10 days indicate that monarchs have reached the northern breeding areas. The arrivals are a bit later than last year but the timing is less important than the numbers of first generation monarchs reaching these milkweed-rich habitats. Judging from the numbers of sightings posted to Journey North (http://www.learner.org/jnorth/) for the period 10-30 May, the numbers reaching the northern states are about half those in these areas last year in this time period. Monarchs are still moving north and many breeding areas, especially those in the East, have not reported monarchs. It is still too early to predict the fall population but the surge of new monarchs that signaled the recovery of the population after the winter of 2000-2001 has not occurred this spring.

Last year at this time I was collecting 25 or more monarchs on two hour field trips for an orientation experiment being conducted by one of my students. In addition to monarchs, there was an extraordinary abundance of migrant butterflies of at least 10 other species that had moved north from Texas. These migrants are missing this spring and it would appear that the conditions in Texas were not as favorable for migrant butterflies, including monarchs, as they were last year. Much of Texas is experiencing drought conditions and recently Austin was 9 inches below normal for the year. Rainfall in Texas was well distributed and abundant in the winter of 2000-2001.

I have only seen 7 monarchs this spring and this is certainly my all time low for this far into the season. A number of eggs and larvae were found during the visit to prairies (23 May) by attendees at the monarch conference last year but we have found no eggs so far this season. Surely there are monarchs in eastern Kansas but the numbers are low.

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3) Degree Days and Monarchs

The developmental rate of monarchs is temperature dependent. Under optimal conditions monarchs can complete development from egg to eclosion (emergence of the adult from the pupa or chrysalis) in 25 days. Cool temperatures delay development and in the early spring monarchs can take 44 and perhaps up to 50 days to reach the adult stage in some cases.

Last month we introduced the term "developmental zero", that point (11.5 C, 52.70 F) at which it becomes so cold for the monarchs that all development ceases. Development will proceed at temperatures above this baseline. Using 11.5 as the baseline, we can establish the number of "degrees days" for each day in a monarch's life whether it is outdoors or indoors. To calculate the degree days for a given day all we have to know is the minimum and maximum temperatures for that day. These are added together and divided by 2. For example, if the temperature in the rearing area in the classroom reaches 25.56 C (78 F*) during the day but drops to 17.78 C (64 F) overnight the mean temperature is 21.67 C (71 F). To obtain the degree days above developmental zero, we subtract 11.5 from 21.67 and we get 10.17. Myron Zalucki (1982) determined that monarchs require 352 degree days to complete development. If we divide 10.17 into 352 this gives us the number of days (34.6) that it will take a monarch to develop at this mean temperature. Conversely, for a monarch that took 25 days to complete development in South Texas this spring, we can estimate the mean temperature this monarch must have experienced; 352/25 = 14.08 degree days/day +11.5 or 25.58 C (78 F). What might appear to be a relatively small difference in temperature to us makes a big difference to the monarchs. However, even though developmental rate increases with temperature, there are limits and as mean temperatures become higher than 26 C development begins to slow. Constant temperatures in the 30 degree range can kill monarch larvae. I will discuss lethal temperatures for monarch larvae at another time. These examples are simplifications but they illustrate the method. Your monarchs may develop faster or slower than Zalucki's degree day model. His experiments were conducted in growth chambers with constant temperatures and ideal host plant conditions. If the results differ from the predicted rates, the challenge is to determine why.

If you attempt to determine degree days outdoors, be sure that your temperature measurements are taken with thermometers that are shielded from the sun but placed close to the feeding larva.

* We should teach our students how to take these measurements in centigrade. Students should be taught how to make the conversions from F to C and the converse. However, the following web site will allow you to make these conversions rapidly and accurately so you can keep ahead of your students or check on their results.

http://www.chemie.fu-berlin.de/chemistry/general/units_en.html

Zalucki, M. P. 1982. Temperature and rate of development in Danaus plexippus L. and D. chrysippus L. (Lepidoptera: Nymphalidae). Journal of the Australian Entomological Society 21: 241-246.

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4) Good Years vs Poor Years

by Chip Taylor

What makes the difference between a good year and a poor year for monarchs? Our assessments of monarch numbers are based on what we can see and what we can measure. The "best" year for monarchs in recent years, and perhaps the best since the colonies were first known to science in 1975, was 1996. In that year Eligio Garcia and his colleagues measured 20.97 hectares of monarchs in all colonies. The "worst" year was 2000 when monarchs only occupied 2.83 hectares. The difference between this high and low is astonishing but not atypical for the kinds of ups and downs exhibited by many insect populations. Nevertheless, the year to year changes in the size of the monarch population beg for an explanation. Scientists studying monarchs are looking for biological and climatic patterns that might help explain these changes. The answer to this question will come from long term studies that detail the factors that regulate reproductive success in the breeding season and describe the death rates of adults during the migratory phase from August to April.

Reproductive success during the breeding season was clearly better in 1996 than it was in 2000, but why? Below are the temperature and rainfall data from two locations, Minneapolis, MN and San Antonio, TX. The former was selected as a representative site for the northern portion of the breeding range and the latter because it represents the conditions for central Texas for the production of the first generation of monarchs in March and April. For brevity, I've only listed average daily temperature and rainfall for these two locations. In Minnesota, the summer was cooler in 1996 with rainfall in the normal range early in the summer but with below average in July and August. Though warmer, rainfall was higher in all months in 2000. In San Antonio, the March temperatures, when the first generation of monarchs is getting started, were lower in '96 than in '00. However, rainfall was below the long term averages for all months in both years. What can we make of this? Did the cool conditions in Texas lead to a large first generation of monarchs that moved north in May and June to be favored by cool weather in the northern part of the breeding range? We don't know. Comparisons of this type will have to be made for entire regions over many years to determine the extent to which monarch populations are influenced by weather patterns.

My intuition tells me that hot summers, even though they can lead to a greater number of monarch generations in some regions of the country, do not necessarily translate into greater fall populations. Cooler may be better provided that enough first generation monarchs arrive in the northern breeding areas from the southern states in May and June. An analysis of this type ignores biological factors and these may be extremely important in some years. Earwigs, fire ants, tachinid flies and perhaps other predators and parasites seem to be favored in seasons with normal and above normal rainfall and these organisms could have a major impact on critical portions of the monarch population in some years. There is also the matter of lag times in the populations of the predators/parasites that might confound interpretation. For example, fire ant populations (and those of other predatory insects) slowly decline when droughts are severe. This allows a measure of escape for the monarch larvae; however, adult longevity and egg laying rate are likely to be negatively affected by the drought as well so the net gain by the monarchs due to the reduction in predators/parasites might be low. However, when conditions improve rapidly due to rainfall, as may have been the case in the spring of 2001 in Texas, the fire ants and predatory insects require several generations and many months for their populations to recover. In this case, monarchs have reduced losses to predators/parasites and a much higher rate of reproductive success than we might have expected on the basis of climate alone.

It will take a number of years to establish the cause and effect relationships that govern monarch populations, yet it will be done. This kind of knowledge is essential for the conservation of the migration and to distinguish between natural and anthropogenic (caused by humans) effects on monarch populations.

* http://climate.umn.edu/hidradius/radius.asp
** http://www.srh.noaa.gov/ewx/html/cli/sat/sclidata.htm
*** http://lwf.ncdc.noaa.gov/oa/climate/online/ccd/nrmlprcp.html

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5) Raising Monarchs in the Summertime

Monarch Rearing Kits are currently available for summertime educational activities so if you'd like to raise monarchs this summer, place your order today via Gulliver's Gift Shop:

http://Shop.MonarchWatch.org

MonarchWatch@HomeEarth.com
3515 Silverside Road, Suite 203
Wilmington, DE 19810

toll-free phone - (800) 780-9986
toll-free fax - (866) 250-6065

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6) Reminder: Order Your Tags Today!

As we mentioned last month, we anticipate running out of tags later in the season as we have done in the past. Nearly half of the tags printed are now spoken for - if you would like to participate in our tagging program this fall, please be sure to get your order in soon so that you will be able to get the tags you'll need.

Head on over to Gulliver's Gift Shop and order your 2002 Tagging Membership and additional tags today!

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7) 15% OFF Summer Reading Specials in Gulliver's Gift Shop!

As you know, we've been adding lots of new products to Gulliver's Gift Shop. The Book and AV aisles have received most of our attention and there are nearly 2,500 titles for you to choose from! We have more than 50 books and 12 videos related to butterflies and moths. All of the books and audio/visual products we carry are nature titles and would be excellent additions to your library. For June you can get them all at 15% OFF!

Planning a trip? Check out the Field Guides Aisle where you will find more than 650 titles that cover almost anything you want to watch or identify. The Field Guides cover North America and beyond. If you need something to keep the kids busy while traveling the Children's Book Aisle has 155 activity books, field guides, and general reading titles that will keep them occupied in the car, hotel or plane.

For the month of June only all of the items in the Book Aisle are 15% OFF (sorry, the Curriculum Guides, Field Guide to Monarch Caterpillars, My Monarch Journal, Monarch Magic, and My Monarch Investigation are not included in this special). Each purchase from Gulliver's Gift Shop helps support the research and educational goals of Monarch Watch.

http://Shop.MonarchWatch.org

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8) CyberSurfari 2002

Monarch Watch has been involved with CyberSurfari, an educational internet treasure hunt, for several years now. We provide monarch-related clues to answers that appear on our website and when a player finds the answer they receive a treasure code and then it's on to the next CyberSurfari "outpost" for another clue. There are 4 or 5 "surfaris" throughout the year and the May/June 2002 CyberSurfari was launched on May 24th. If you'd like to participate or just get more information, head on over to

http://www.cybersurfari.org/

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9) Adopt-a-Classroom

Now that another school year has come to a close, please consider sending used (but not used up ;-) school supplies to us in support of our Adopt-a-Classroom program. We will organize these materials along with the new supplies and other donations we receive and take them to Mexico in January to be distributed to the rural schools within the Monarch Reserve.

For more information about this wonderful program, please visit

http://www.MonarchWatch.org/conserve/adopt.htm and

http://www.MonarchWatch.org/aac/2002/

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10) How to Unsubscribe from this Update

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Thanks!

Monarch Watch
http://www.MonarchWatch.org
monarch@ku.edu