Hosts or Prey
Prickly pear cacti including Nopalea, Opuntia, and Platyopuntia spp. Depending on the situation, these cactus-feeding scales are beneficial as discussed here or cochineal scales are pests.
Identification
Dactylopius species can be recognized by the white wax that adult female scales and nymphs secrete covering their bodies where they feed on Nopalea, Opuntia, and Platyopuntia species cacti. At least 11 Dactylopius species of cochineal scales occur in California. Because of their similar appearance it may not be possible to reliably distinguish one cochineal scale species from another in the field. Expert preparation of specimens and examination of microscopic characters can be necessary to reliably distinguish the species.
The most common cochineal scales in California appear to be D. confusus, D. opuntiae, and D. tomentosus. In general
- California cochineal scale, D. confusus, females and settled nymphs are imbedded in more profuse white wax secretions than those of D. opuntiae and D. tomentosus.
- Opuntia cochineal scale, D. opuntiae, usually occurs in groups around the base of prickly pear spines. The white covers secreted by each female are usually separate.
- Tomentose cochineal scale, D. tomentosus, produces much less wax than the other two species. Its wax is more transparent and consists of relatively straight filaments. The red body of settled tomentose cochineal scales is usually visible through the wax filaments.
The bodies of all stages of these scales are deep red to slightly purplish (carmine). This may not be apparent because except for the crawler stage (mobile first instars) and adult males the bodies of cochineal scales are encased in sticky, white wax. The reddish coloration of their bodies becomes apparent when the scale covering is punctured causing the wax cover and surrounding areas to become stained carmine.
Adult females are oval and 1/12 to 1/5 inch (2–5 mm) long. The body has a wrinkly, segmented appearance and no obvious appendages. Eggs are bright red and oval. They occur beneath white wax secreted by the adult female scales. Eggs and crawlers are less that 1/25 inch (1 mm) long. The crawlers are oval with distinct legs and long filaments. Settled nymphs resemble adult females.
Adult males are not commonly seen. They are delicate, brownish insects with long antennae, whitish wings, and two long tail filaments.
Life Cycle
Cochineal scales develop through three life stages: egg, nymph, and adult. After hatching from an egg the female crawlers commonly walk upward on plants where they become dispersed by the wind. Male crawlers tend to remain on the plant where they hatched. Males commonly disperse when they mature into winged adults.
Adult females live about 2 months during which each produces several hundred eggs. Egg to reproductive adult development time is about 3 weeks when temperatures are warm. Dactylopius species have multiple generations per year.
Habitat
Nopalea, Opuntia, and Platyopuntia species cacti occur throughout much of the world where they are native or have been introduced. They are serious ecological and economic weeds in some situations. In other situations, prickly pear are aesthetically, ecologically, and economically valuable plants. For example, D. coccus has been cultured for centuries because the scale bodies are the natural source of bright red carmine dye. Where desirable prickly pear cacti are being damaged by these scales, see Cochineal scales—Dactylopius spp. for management recommendations.
Of the Dactylopius species known to occur in California it was the deliberate introduction of the opuntia cochineal scale, D. opuntiae, from the mainland of California to Santa Cruz Island, California that provided successful classical biological control of weedy Opuntia species. The scale caused a tremendous reduction in cactus abundance and the land area they covered. This great reduction in cactus abundance allowed restoration of the island's vegetation for the ongoing ecological benefit of native wildlife. Biologically controlling the cacti also benefited commercial cattle ranching that occurred on this formerly private island until it was acquired by the National Park Service and Nature Conservancy.
Species
The 11 Dactylopius species known in California are: Dactylopius andersoni, D. confusus, D. coccus, D. dudleyi, D. indicus, D. mcnabiana, D. menabiarra, D. opuntiae, D. tomentosus, D. salinus, and D. sequoiae. All are commonly called cochineal scales. Cochineal insect is the official common name of D. coccus.
More Information
- Biological Control of Prickly Pear Cacti on Santa Cruz Island, California; UC Riverside, Hilgardia
- Cochineal Carmine: An Ancient Dye with a Modern Role, Endeavour
- Dactylopius Costa 1829 (Dactylopiidae), ScaleNet, United States Department of Agriculture
- Dactylopius opuntiae (Cockerell), Arthropoda Mexicana
- Insects Control Prickly Pear Cactus, UC Riverside, California Agriculture
- Life Cycle and Fecundity of Dactylopius opuntiae (Hemiptera: Dactylopiidae) in Opuntia ficus-indica (Caryophyllales: Cactaceae), Agrociencia
- Monarch, collections database, California Academy of Sciences
- The Scale Insects of California Part 2: The Minor Families (Homoptera: Coccoidea), California Department of Food and Agriculture
- On the Status and Identity of the Cochineal Insects (Homoptera: Coccoidea: Dactylopiidae), Journal of the Entomological Society of South Africa
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hemiptera
- Family: Dactylopiidae
