Chilocorus stigma (Say)
by Kirsten Fondren, Department of Entomology, Michigan State University, East Lansing, MI 48823
Nearly all species in the genus Chilocorus are predaceous on scale insects, although some will accept aphids or adelgids as prey (Gordon 1985). Most species are tropical, but seven species of Chilocorus are native to the United States. Two species, C. kuwanae and C. bipustulatus, have been introduced for biological control. However, the native Chilocorus stigma is the only one that occurs in most of the United States. It does not occur west of the Sierra Nevada. C. stigma is synonymous with C. bivulnerus Mulsant.
C. stigma adults appear shiny black with a large red spot in the center of each elytron. Adults average 3.75-5.0 mm in length. The body is completely black except for the abdomen, which is yellow or red. A few other native Chilocorus species closely resemble C. stigma, but for the most part they are found in California where C. stigma does not occur (Gordon 1985). The introduced species C. kuwanae appears similar but can be distinguished by the appearance of the spot on its wings (see page on C. kuwanae). Larvae are black or grey and spiny in appearance. Eggs are small (about 1.1 mm long), orange, and laid on their sides either singly or in small groups (Muma 1955).
Chilocorus species typically prefer arboreal habitats. They have been identified as beneficial natural enemies in orchards, tree plantations, and forests. In Michigan, C. stigma is often found in Christmas tree plantations, and forests where scale insect infestations are found.
The genus Chilocorus consists mostly of armored scale insect predators. C. stigma is an omnivorous predator of several scale insects, aphids, and mealybugs (Muma 1955). It has been reported often as a predator of the pine needle scale (Chionaspis pinifoliae) (Cumming 1953, Neilsen and Johnson 1973, DeBoo and Weidhaas 1976). It has been observed attacking beech bark scale (Cryptococcus fagisuga) in Michigan. Muma (1955) found it associated with the Florida red scale (Chrysomphalus aonidum) in citrus groves.
C. stigma completes two generations in the northern U.S. (DeBoo and Weidhaas 1976). In Florida, it can complete several generations a year (Muma 1955). In cold areas, overwintering adults become active in early spring (April or May). Mating begins shortly and continues for about three weeks. Eggs are laid soon afterwards. Larvae emerge in late May and undergo four instars before pupating (Muma 1955). DeBoo and Weidhaas (1976) observed that in New York State, the overwintering adults continue to feed through June and early July, after first generation larvae have hatched. First generation adults mature in early to mid July. Mating and oviposition continue as before, and second generation larvae are observed beginning in mid July through early August. Adults emerge in midsummer and overwinter in ground litter.
Some workers report that C. stigma can be a highly effective predator of pine needle scale (DeBoo and Weidhaas 1976). Cumming (1953) states that C. stigma greatly reduced populations of pine needle scale in localized areas of Saskatchewan. Others dispute the claim that it is important in the absence of other predators (Muma 1955). Cooper and Crenshaw (1999) found it only rarely associated with the pine needle scale in north central Colorado. Its impact on the beech bark scale in Michigan is not yet known.
Like most beneficial insects, C. stigma is susceptible to broad-spectrum insecticides. Using alternative control treatments such as dormant or horticultural oils may be less harmful to the lady beetles.
Avoiding or reducing the use of broad-spectrum insecticides will help conserve beneficial natural enemies such as C. stigma. Preserving refuges such as windbreaks or forested edges will give C. stigma a place to survive and recolonize scale-infested fields or orchards after disturbances. In Christmas tree plantations, selective spraying of the most severely infested individual trees near market, when possible, is one way to conserve natural enemies (DeBoo and Weidhaas 1976).
Currently C. stigma is not commercially available in the United States. Developing an efficient and productive rearing method for C. stigma could be an important contribution to biological control or integrated pest management programs.
Cooper, D.D. and W.S. Crenshaw. 1999. The natural enemy complex associated with the pine needle scale, Chionaspis pinifoliae (Fitch) (Homoptera; Diaspididae), in North Central Colorado. J. Kan. Ent. Soc. 72(1):131-133.
Cumming, M.E.P. 1953. Notes on the life history and seasonal development of the pine needle scale, Phenacaspis pinifoliae (Fitch). Can. Entomol. 89(9): 347-352
DeBoo, R.F. and J.A. Weidhaas, Jr. 1976. Studies on the predation of pine needle scale, Phenacaspis pinifoliae Fitch, by the coccinellid, Chilocorus stigma Say. Plantation research: XIV. Report CC-X-119. Chemical Control Research Institute, Canadian Forestry Service, Department of the Environment, Ottawa, Ontario.
Gordon, R.D. 1985. The Coccinellidae (Coleoptera) of America North of Mexico. J. New York Ent. Soc. 93(1).
Muma, M.H. 1955. Some ecological studies on the twice-stabbed lady beetle Chilocorus stigma (Say). Ann. Ent. Soc. Am. 48:493-498.
Nielsen, D.G. and N.E. Johnson 1973. Contribution to the life history and dynamics of the pine needle scale, Phenacaspis pinifoliae, in central New York. Ann. Ent. Soc. Am. 66: 34-43