A January 2014 report from the monarchs’ overwintering forest areas in Mexico indicated that only 1.65 acres were occupied by monarchs this winter. That makes this the third straight year of steep declines. The overwintering areas have been monitored since 1993 and the largest occupied area was 45 acres in 1996.
A number of factors have contributed to the decline of the monarch population in recent years. Unusually hot weather in the spring of 2012, unusually cold weather last spring, and the loss of habitat throughout the Great Plains have combined to create hardships for the insects. Higher grain prices in recent years have resulted in more land being cultivated for crops and more weed-free farming techniques have reduced the number of milkweed plants in most agricultural fields. Several milkweed species are still common in Missouri, but in highly agricultural areas the plants can be too scarce to support migrating monarchs.
Monarchs lay their eggs on milkweed plants. Missouri has 17 native species of the plants. Caterpillars emerge from the eggs and feed on the leaves and stems. After feeding and growing for about two weeks, the caterpillar forms a chrysalis and pupates (transforms from caterpillar to adult butterfly). The adult butterfly emerges from the chrysalis after about 10 days. Adults live from 2 to 6 weeks and die after mating and laying eggs. The entire life cycle of the first three generations lasts 6 to 8 weeks each and four generations occur each year. The adult butterflies of the fourth generation migrate to Mexico and live until they lay eggs on their way back north the following spring. So the monarchs that you see moving south in the fall are four generations removed from the ones that headed north in the spring.
Planting milkweeds, especially in areas where they are currently scarce, can help monarchs be more successful in rearing new generations. Milkweeds are appropriate for use in home landscape plantings and several species are popularly used, especially by gardeners who enjoy helping monarch butterflies. Several milkweed varieties grow well in Missouri and range from 2 to 6 feet tall in a variety of colors. These include marsh milkweed, purple milkweed, common milkweed, and butterfly weed.
- Copyright Schurz Communications 2014