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Chilocorus stigma, commonly known as the twice-stabbed lady beetle, is a native resident of the United States and Canada but does not live west of the Sierra Nevada. The two-stabbed lady beetle Chilocorus orbus is found widespread in California. It also lives in Oceania and has been introduced to Hawaii. It is shiny black in color, and there is one red spot on each elytron. The remainder of the body is black as well, but the abdomen is either yellow or red in color.
Habitat and pests eaten
C. stigma mainly lives within terrestrial/arboreal habitats, primarily feeding of aphids found in these habitats as well as scales (such as pine needle scale, beech bark scale and Florida red scale) and mealybugs. It is a beneficial insect, and is useful in both natural wood stands and commercial forests such as orchards and citrus groves. It is beneficial against non native species. An introduced Hemlock pest, the elongate hemlock scale (Fiorinia externa Ferris), which has been doing considerable damage to Hemlock trees throughout North America, can be moderately controlled by the presence of C. stigma. C. stigma is currently not a lady beetle that can be sold for commercial use in orchards or on farms.
Life cycle and issues
C. stigma usually completes two lifecycles a year in Canada and the North United States but may complete several lifecycles a year further down South. They overwinter in ground litter during the colder months. C. stigma has been shown, like other ladybeetles, to be susceptible to the use of insecticides diminishing its population in the wild. In order to preserve the benefits of this insect, pesticide users are encouraged to use natural alternatives to pesticide in order to curb the decline of C. stigma.
The chromosomes (karyotype) of Chilocorus stigma vary from one individual to another, in both the number of chromosomes (aneuploidy) and their structure (chromosomal polymorphism). The variability occurs as a result of chromosome fusions or disassociations.
- Jerry A. Powell and Charles L. Hogue (1980). California Insects. University of California Press. ISBN 9780520037823. p. 299
- "Chilocorus stigma". Integrated Taxonomic Information System. Retrieved 30 April 2006.
- United States Department of Agriculture. "Elongate hemlock scale". Retrieved 30 April 2006.
- Smith, S.G. (1956). "Extreme chromosomal polymorphism in a coccinellid beetle". Experientia. 12 (2): 52–53. doi:10.1007/bf02164672.
- Smith, S.G. (1962). "Tempero-Spatial Sequentiality of Chromosomal Polymorphism in Chilocorus stigma Say (Coleoptera : Coccinellidae)". Nature. 193 (4821): 1210–1211. doi:10.1038/1931210a0.
- White M.J.D. 1973. The chromosomes. Chapman & Hall, London. p169