Lema cyanella

Linnaeus, 1758

Californian Thistle Leaf Beetle

Lema cyanella is a leaf beetle in the Chrysomelidae investigated as a agent for Canada thistle (Cirsium arvense). In Europe, it has been observed breeding primarily on C. arvense, though laboratory studies demonstrate broader feeding and reproductive capacity on Cirsium, Carduus, and Silybum . The was introduced to New Zealand in 1981 and evaluated for release in North America. Females lay an average of 1564 , with development from egg to taking approximately 17.6 days under controlled temperature conditions.

Lema cyanella by (c) janet graham, some rights reserved (CC BY). Used under a CC-BY license.

Lema cyanella by S.E. Thorpe. Used under a Public domain license.

Lema.cyanella.-.calwer.42.09 by Emil Hochdanz
. Used under a Public domain license.

Pronunciation

How to pronounce Lema cyanella: /ˈlɛmə saɪəˈnɛlə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Images

Distribution

Native to the Palearctic region, with records from Spain, France, the United Kingdom, Germany, Italy, the Czech Republic, Austria, Hungary, Serbia, Bosnia and Herzegovina, Denmark, Norway, Finland, Russia, and Lithuania. Also recorded in Asia (India, Taiwan, South Korea, China) and Oceania. Introduced to New Zealand in 1981, where establishment has been limited. Evaluated for introduction to North America as a agent.

Diet

and larvae feed on thistles in the Cirsium, Carduus, and Silybum. Cirsium arvense (Canada thistle) is the main in Europe.

Host Associations

Cirsium arvense - primary Main in Europe; target for
Cirsium drummondii - laboratory Preferred over C. arvense in laboratory choice tests
Carduus spp. - laboratory Supports feeding and in laboratory conditions
Silybum spp. - laboratory Supports feeding and in laboratory conditions

Life Cycle

Development from to takes 17.6 days at 25°C day/20°C night (average approximately 23°C). Females lay an average of 1564 eggs.

Behavior

Exhibits feeding and oviposition preference hierarchy, with flowering plants preferred over stunted conspecifics. In field cage tests, concentrated feeding and -laying on individual Cirsium drummondii plants that were thriving, even when other host plants were available.

Ecological Role

Candidate agent for Canada thistle (Cirsium arvense), a significant agricultural weed. Based on comparative evidence with other thistle-feeding insects, predicted to concentrate breeding on introduced Cirsium arvense without damaging native Cirsium in North America.

Human Relevance

Imported to New Zealand in 1981 and released in 1983 as a agent for thistles, with additional mass-rearing and distribution in the 1990s; establishment has been limited. Evaluated for release in North America to control Canada thistle in wheat fields. Field-collected colonies may carry , requiring -free stock for intentional releases. No economic plants are attacked.

More Details

Biological Control History

Initial introduction to New Zealand in 1981 used -free progeny released in 1983, which failed to prosper. A second introduction in 1990 with mass-rearing and distribution in the 1990s also had limited success, though some establishment appears to have occurred. This pattern paralleled experience in Canada.

Disease Risk

Field-collected beetles from Germany were found infected with , a microsporidian . Recommendations for North American release emphasize the need for -free colonies to avoid introducing alongside the control agent.