Galapagos Species Database

The Galapagos Species Database shares the information about the species from our Natural History Collections.

Icerya purchasi (Maskell, 1878)

Escama algonodosa, Cottony cushion scale

Cottony cushion scale (Icerya purchasi) infestation. Photo: H. Rogg, CDF.
Cottony cushion scale (Icerya purchasi) infestation. Photo: H. Rogg, CDF.

The Cottony Cushion Scale is a self-fertile hermaphrodite (has both male and female organs). The brownish adult (3 mm long) produces a white ridged cottony egg sack that is attached to her rear (6 mm long). 600-800 eggs are extruded into the sack and stay there during development to emerge as small crawlers that disperse. The crawler moults 3 times before becoming an adult. The final instar and adult stage are sedentary and feed on sap. They form large colonies along the branches and stems of plants and are often protected from predators by ants which, along with a black sooty mould, feed off a sugary honey waste produced by the scale.












Taxon category: Accepted

Taxon origin: Introduced - established


Preference for an altitude zone in Galapagos: Coastal zone - high altitude dry zone

Substrate or host preferences: 80 plant species

Feeding type: Phloemivorous

Feeding preferences: Highly polyphagous, feeds on a wide variety of plant species.

Trophic role: Parasite

Reproductive biology: Cottony cushion scales have four ('female') or five (male) stages. As with all scale insects, the females do not produce wings and look similar to the immature stages. The males possess a single pair of dusky wings. However the 'females' are actually hermaphrodites with fertilization occurring between the eggs and the sperm of the same individual. Sexually functional males are occasionally produced from unfertilized eggs. Adult females produce 500-2000 bright-red, oblong eggs over a period of 2-3 months. The number of eggs produced depends on the size of the body, condition of the host and climatic conditions. After leaving the egg sac, the crawlers settle along the midribs and veins of the leaves. The next two instars migrate to the larger twigs and branches and eventually moult into the adult 'female'. There are 2-4 generations each year.

Distribution origin: Australia

Dispersal propagule: Los "crawlers", como otras escamas pueden ser distribuídas por el viento, insectos voladores y pájaros.

Natural enemies: Rodolia cardinalis

Associated species in Galapagos: No


Mode of introduction: Accidental

Introduction Pathway: Contaminant

Subpathway: Contaminant on plants (inc. seeds and plant associated material)

Introduced status: Naturalized

Invasive status: Invasive

Invasion risk score: Extreme risk

Impact in Galapagos: In Galapagos the species has been recorded to feed on 80 plant species, of which 31 are endemic, causing a decline in their populations, and affecting the food source of endemic herbivores. Its impact on mangroves was sufficiently intense to cause concern about losing this unique habitat.

Impact elsewhere: Weakens plants by sucking sap, which impacts agricultural crops and threatened species.

Control History in Galapagos: A multi-agency review concluded that biological control was the only feasible option to manage this species. The vedalia beetle (Rodolia cardinalis) was chosen because of its proven success and high specificity to Icerya purchasi. Extensive trials were carried out in quarantine in 1999 to ensure its specificity, and to quantify the impact of the scale on native plants. Following approval by the National Park Service R. cardinalis was released onto 11 different islands between 2002-2005. Monitoring was carried out soon after release, and again from 2009 -2011. Results indicate the the beetle is effectively controlling the scale and low levels, and also maintaining its own population. Five yearly monitoring programs will continue to be necessary to ensure that the species is being effective.

Control methods elsewhere: Simple control methods include spraying with detergent mixture or using insecticides. Preventing ants from protecting the colonies allows natural predators to remove the scale. Biological control is also commonly used throughout the world.

Year of first record: 1982


Map of specimen collection localities or observation records for this species in our collections database.

Distribution: Widely distributed across the archipelago, including the islands of Baltra, Floreana, Isabela, San Cristóbal, Santa Cruz, Seymour Norte, Santiago, Fernandina, Santa Fé, Marchena, Pinta, Pinzon, Rabida, Genovesa, and Champion. Originally from Australia. First recorded in Galapagos on San Cristobal in 1982.


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You are welcome to download and use the information found in this page, acknowledging the origin of the data.
This page should be cited as follows:
"Galapagos Species Database, Icerya purchasi", dataZone. Charles Darwin Foundation, Accessed 28 May 2024.