|scientific name Perillus bioculatus |
common name Two-Spotted Stink Bug
Habitat is unknown.
Strickland Museum collections range from May to December; McPherson (1982) notes Illinois records between January and October.
This species has both a red and yellow form, and both are slightly more robust around the pronotum and posterior abdomen thus giving them a very subtle hourglass shape as opposed to P. exaptus' distinct oval shape. The colouring of the red form is primarily in the pronotum and scutellum. In these structures the colouring appears only around the margins, except that in the pronotum a medial red strip separates two large black spots, and on the scutellum the basal margin remains black. The characteristic black spots on the pronotum also aid in distinguishing this species from P. exaptus. The margins of the connexivum and basal portions of the hemelytra are also red coloured. In the yellow form, slight differences occur in the location of the colouring. The pronotum still has a thick red bar along its posterior margin; however the black spots are surrounded by yellow. Additionally, the margins of both the corium and scutellum are completely lined with yellow enclosing blackened regions in the centres of these structures. As in the red form, the margins of the connexivum and basal portions of the hemelytra are yellow as well. The fore-femora of both forms have a ventral, elongated spine contrasting the stubby tubercle present in P. exaptus. This species is much larger in size than P. exaptus; length 8.5 to 11.5 mm (Blatchley 1926; McPherson 1982).
The species has 2 to 3 generations per year, with the final generation hibernating over the winter months. Eggs are laid in early spring in batches of 10 to 25. After roughly 5 to 8 days of incubating at temperatures between 20° C and 25° C the eggs hatch. The first four nymphal instars are gregarious with phytophagous feeding which is unlike that of species of the genus Podisus. Their predatory behaviour only appears after the first molt. Immatures require about 3 weeks to fully mature into adults. Once mated females can deposit between 100 and 200 eggs (De Clercq 2000).
This species has apparently been mass-reared for biological control of the Colorado potato beetle (McPherson 1982).
The species is a significant predator of larvae of Coleoptera, especially that of the Colorado potato beetle, Leptinotarsa decemlineata (Chrysomelidae) (De Clercq 2000). It has also been observed feeding on the leaves of potato plants despite its typical predatory feeding habits (McPherson 1982).
This species is widespread across North America including Mexico, ranging from coast to coast and north to but not including the Canadian Territories (Henry and Froeschner 1988; Maw et al. 2000). It has also been introduced into Europe as it is a significant predator of economically important pests (Henry and Froeschner 1988). The north-south range of this species in Alberta lies between Edmonton and Lethbridge. From east-west, it has been collected from Medicine Hat to the eastern front of the Rocky Mountains.
Reproduction and development is highly dependent on temperature, prey species and the host on which the prey is feeding. This is particularly evident when considering the two very different looking forms of the species. Traditionally, the yellow form, P. bioculatus var. clanda (Say) had been elevated to species level status but after thorough investigation of the causes of pigmentation variation has been described as merely a colour variation of P. bioculatus. These studies revealed that the red pigments inherent in the red form are actually dependent on pigments consumed from their diet on L. decemlineata and that these are further dependent on the temperatures of their surroundings (McPherson 1982).
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