April’s Butterfly of the Month is Danaus plexippus, the Monarch.
Range: North America- from southern Canada to Mexico 
How to Attract them to Your Backyard: Ann recommends milkweed and lots of it! If you aren’t a fan of common milkweed, check out butterfly weed. It’s attractive, and the monarchs will love it. She also recommends planting the milkweed in patches, not just single plantings. In addition to milkweed, have lots of colored flowers available…zinnias are a wonderful nectar source.
May be confused with: Viceroy (we’ll do a post on them soon!)
Size: ~3.5″ to 5″
Season: End of May through September in Massachusetts; In fact, you may see even more in September as the individuals in Canada begin their migration.
Female vs. Male: Difficult to distinguish; but you can look for small black dots on the lower wings which are scent glands only found on the male 
Life Cycle: Monarchs lay single eggs on the underside of milkweed leaves. After hatching, the monarch caterpillar devours the milkweed. When they’ve eaten enough, they hang upside-down to form their chrysalis. The green chrysalis have a row of tiny golden beads- it looks like actual gold! The final generation of the season (generation 3 in our area) will migrate to a warmer area for the winter. West coast monarchs head to southern California, while east coast monarchs head to Mexico. The population overwinters in Mexico before returning north in the spring. 
- They are the only butterfly in the world to have a true migration. We’ll discuss this migration in greater depth this fall!
- A compound they ingest from the milkweed makes them slightly poisonous to birds and other predators- a great defense mechanism
In Our Habitat: The monarchs are a pleasure to have in our habitat! They are very social butterflies and interested in people. They love the sun and warm temperatures, so tend to be more active in the afternoon on sunny days (~11am to 4pm), particularly when temperatures are in the 70s. You can often find them enjoying the sun by hanging on the screens, or eating from brilliantly colored flowers. They get pretty engrossed in eating, so are easy to photograph. Ann has placed zinnias both in hanging baskets, and close to the floor, so there are plenty of opportunities for viewing!
Be sure to stop by to see our monarchs starting in May!
- Burris, Judy, and Wayne Richards. The Life Cycles of Butterflies: From Egg to Maturity, a Visual Guide to 23 Common Garden Butterflies. North Adams, MA: Storey Pub., 2006. Print.