Large milkweed bug

Description

Oncopeltus fasciatus, known as the large milkweed bug, is a medium-sized hemipteran (true bug) of the family Lygaeidae. It is distributed throughout North America, from Central America through Mexico and the Caribbean to southern areas in Canada. Costa Rica represents this insect's southern limit. It inhabits disturbed areas, roadsides, and open pastures. Due to this widespread geographic distribution, this insect exhibits varying life history trade-offs depending on the population location, including differences in wing length and other traits based on location. Adults can range from 11 to 12 mm in length and have a red/orange and black X-shaped pattern on their wings underneath the triangle that is typical to hemipterans. This feature makes the bug easily seen, acting as an aposematic warning to predators of distastefulness. O. fasciatus exhibits Müllerian mimicry and is noxious to predators. The ventral side of the fourth abdominal segment bears a black band in the male and two black spots in the female. Juveniles are born mostly red with black antennae and a few black spots, throughout growth the black spots are developed as well as wing pads. Eggs of this insect are bright orange and easily detectable. This large milkweed bug is a hemimetabolous insect, meaning it grows in stages called instars and goes through incomplete metamorphosis, exhibiting small changes throughout development such as coloration changes, development of wings and genitalia. O. fasciatus begins as an egg and experiences four nymphal stages over 28–30 days before moulting to adulthood. Females become sexually receptive within a few days of adulthood. Geographic location has a large effect on egg production rate and clutch size, although the intrinsic increase in reproduction depends on to what the individual is acclimated. For example, two close populations (60 km apart) residing on a sharp incline have differing optimal reproduction temperatures, where the cooler (higher) adapted population is at 23 °C and the warmer (lower) population is adapted to 27 °C. Highest clutch size occurs in Puerto Rico, Florida, and Texas populations at 30-50 eggs per clutch. Lowest clutch size was found in California at 25-30 eggs per clutch. Iowa and Maryland (northern populations) exhibited a clutch size in between the two extremes from 25 to 35 eggs per clutch.