This is on the scientific side of popular science: entertainingly written, and explains everything it's talking about, but does assume you're comfortable with scientific terminology and with learning more scientific terminology. Very much university-level - but I'm still going to lend it to my eight-year-old friends' son, who's currently nurturing a swanplant and monarch caterpillars, if only for the amusement value of watching how well he copes (or doesn't).

Anyway so monarchs! and milkweed, because apparently the term "swan plant" (that we use in New Zealand) hasn't caught on in the US despite the seed pods looking exactly like swans! Short version: monarchs are terrible pollinators and milkweed would rather not be eaten by its caterpillars. So it makes itself super poisonous via cardenolides. So monarchs (and a few other species specialising in other parts of the plant) have mutated themselves so they can nom the plant anyway and become poisonous themselves, a fact that they advertise to potential predators via bright colouring. In fact if a butterfly has been infected with parasites she might lay her eggs on an even more poisonous variety which is a bit harder for the caterpillars to eat but kills off the parasites: that's right, butterflies self-medicate. Sadly some predators have worked out which parts of the caterpillar and/or butterfly they can safely eat - and indeed the plant can send out pheromones to attract such predators - and thus the circle of life continues.

In the US, monarchs also migrate the heck out of the continent and literally weigh down trees as they overwinter; however they have different behaviour in New Zealand (and other areas they're not native to) which sadly the book doesn't get into. It discusses the declining North American population and various hypotheses for why; it seems to treat fairly even the hypotheses the author doesn't agree with.

Fantastic state-of-current-knowledge of a specialised but accessible field, well worth the read. ( )

Very interesting and informative. A scientific presentation about the life of Monarchs, Milkweeds and their interactions. Stick with it and there is a really interesting analysis of the current status of Monarch Butterflys and their future. He challenges a lot of quick guesses about what is affecting their populations. ( )

A white, yellow, and black-striped caterpillar is transformed into a beautiful black, orange, and multi-colored butterfly. The author traces the migration and transformation from a caterpillar eating a milkweed leaf, to a chrysalis undergoing metamorphosis, to the emerging butterfly and its migration. Although the writing is at an eleventh grade level, the first person presentation is easy to follow and understand. Besides the general reader, the book is appropriate for general public, high school, and academic library collections. Color photographs suitable for framing and figures highlight key points. Extensive endnotes by chapter include page numbers, comments, and source material. A list of illustrations, acknowledgments, image credits, and an index are included. ( )

I suppose you know this means War

The Hundred Years War has nothing on the Monarchs and the Milkweed. They’ve been going at it for 350 million years now. Unlike the heart-warming mutualistic, symbiotic relationships we read about in nature stories, the monarch butterfly does nothing for the milkweed but destroy it. And the milkweed spends all its energy actively fighting off the monarchs. Nobody is ahead for long. But it reveals the marvels of both species as they coevolve. Monarchs and Milkweed examines them and this relationship in extraordinary detail. This is Anurag Agrawal’s life, and it is clearly fascinating as well as fulfilling.

Monarchs grow fast. Eggs hatch in a few days, caterpillars feed for up to two weeks. The chrysalis forms in minutes, hardens in a few hours, and butterflies emerge in one week. That new generation repeats the process further north, so that four generations are added every summer as the butterflies make their way north from Mexico. And then back, gliding on thermals several thousand feet up.

Milkweed has evolved to hide its firepower below ground in a fat root system. It has a gooey white latex poison in its veins (above ground), which hardens in seconds on invaders who pierce a leaf. It grows bothersome hairs on its leaves to keep the interlopers at bay, and regrows from its energy supply as needed. It uses volatile organic compounds to annoy pests and attract their enemies. Only 11 insects have mastered feeding off milkweed – and live to tell about it.

60% of monarchs die on their first bite into a milkweed leaf, as sticky, fast drying white latex gushes out and drowns them and/or glues their mouths shut. With all the other threats around, there’s a one in ten chance of a Monarch egg making it to reproductive maturity. The females deposit just one egg per plant, because the nascent Monarchs are cannibalistic, eating their own and any other egg shell until they’re ready to attack the milkweed.

It’s a remarkable and unexpected story, told in appreciative detail. Agrawal has peppered the book with absolutely marvelous illustrations by Frances Fawcett, and gorgeous macroscopic photos by Ellen Woods, who (deservedly) get photos in the Acknowledgements. Altogether, it is comprehensive, fast-moving and varied. Now if we could only get them to stop stripping out the forests in Mexico…

David Wineberg ( )