Since several different species of bugs feed on the milkweed plant it may be difficult at first to distinguish the interesting little creature known as the large milkweed bug. Most will appear during late spring or early summer and can be found on the underside of the milkweed plant leaves or within the flowers. But if you live in the northern half of the country you may not find a trace of the large milkweed bug until around mid July.
Many of the adults that appear in the southern regions make a long migration north causing their later appearance in these areas. This is a shy little insect no more than one half inches long. Move cautiously when you approach the milkweed plant since the large milkweed bug is known to drop from the plant to the ground when it is bothered. This tiny insect will be black on the top and bottom part of its body with two distinct red bands running across its body. With both the large and the small milkweed bug there is also a triangular shape in the area where the wings meet.
One of the more interesting aspects of insects that feed on the milkweed plant is that most of them tend to maintain a consistent coloration of red and black. Studies have suggested that the possible cause for this is a poisonous resin compound that is found in certain varieties of milkweed to which the insects that live and feed on these plants have built immunity. It is also believed that the coloration of these insects could be a form of warning predators to stay away. Interestingly the beautiful Monarch butterfly, which takes on the black and red coloration, is known to feed on the milkweed plant as larvae.
When you observe the large milkweed bug as it munches on the milkweed plant, usually attacking the seeds or pods, you may notice two that are attached but facing opposite directions. In some cases it may even appear that the female is dragging the male along behind her. This behavior is part of the mating ritual and when the weather is warmer can last for up to half an hour. If the weather is cooler this mating behavior has been known to last for a full day or longer. Once the mating is complete the female will lay her eggs in small clutches that are comprised of around fifteen eggs on the bottom side of the milkweed plants leaves.
The young nymphs can be observed feeding in groups on the plant within three to five days. Since the large milkweed bug is from the Hemiptera order or order of true bugs, the nymphs gradually go through metamorphosis and five different molts can be observed within the next month to six weeks. After the final molt the nymphs have become adults and can fly. In most cases the adult females will produce around three broods during one mating season with the average life expectancy of the adults being around six weeks.
As the colder months approach many of the large milkweed bugs in the northern areas migrate by flying to the warmer southern areas. Those that stay behind, including the eggs and nymphs, die as the cold moves in. In warmer climates this insect will hibernate as an adult during the winter months and then reappear to feed, mate or migrate north the following summer. One of the more interesting characteristics of this insect is its ability to fall to the ground and remain completely still for minutes at a time when it is startled.
Studies suggest that this is possibly a form of protection that gives this insect the appearance of being dead. It is not uncommon to see several large milkweed bugs dropping from the same plant onto the ground. There they remain motionless until it is felt that the danger has passed. Then, just as suddenly as they have fallen from their perch, they will all begin moving at once as they scurry back up the stem of the milkweed plant.
The large milkweed bug is in the Lygaeidae family, as is the small milkweed bug, and from a species known as Ocopeltus fasciatus. While the small milkweed bug resembles its larger counterpart there are distinctive differences in the size of these two insects that aid with their identification.