Seed bugs are named because most species in their family eat seeds. Included in this group of true bugs are the colorful milkweed bugs but also a number of less exciting brownish bugs. Like many other true bugs in the suborder Heteroptera, members of this family have an X on their backs caused by the way the wings fold together.
Below are some commonly seen members of this family.
The small milkweed bug (Lygaeus kalmii) is a widespread species usually found in open, grassy areas where its principal food plants (milkweeds) are growing. They eat a variety of foods, however, including flower nectar, sap from milkweed seeds, and a variety of scavenged foods. They are also predators of caterpillars as well as the adults, larvae, and pupae of flies, bees, and beetles. Apparently, once milkweed seeds are maturing around midseason, small milkweed bugs mainly eat them.
The large milkweed bug (Oncopeltus fasciatus), with its bold black and orange pattern, is one of the most beautiful of the true bugs. It is one of several species in its genus, with all having similar coloration but different patterns. Females deposit eggs in or among the pods of milkweed plants in groups of about 30 eggs. A single female can deposit more than 2,000 eggs during her adult life, which is about one month. Large milkweed bugs overwinter as adults, and they usually don't survive Missouri winters. Northern populations, including those in Missouri, are migratory. Adults fly south in fall, and our state is gradually repopulated each spring and summer from populations that survive winters to our south.
The white-crossed seed bug, or ragwort seed bug (Neacoryphus bicrucis), is another attractive insect, with a prominent thin-lined white X dividing zones of red and black. Apparently, it can survive on a variety of host plants, but groundsels and ragworts (Senecio spp.; in the sunflower-daisy family), are a favorite. Like most other seed bugs, this insect usually is seen in open areas, where its food plants are abundant.
The sycamore seed bug (Belonochilus numenius) is an elongated, mottled brown bug with a proboscis (mouth tube) nearly as long as its body. It's named for its food and is widespread in the eastern United States.
Neortholomus scolopax (no common name) is another mottled brown seed bug with a widespread distribution. Common and sometimes abundant in dry grassy areas, apparently it is polyphagous (able to feed on a variety of plants).