Twenty-spotted lady beetle

Description

Psyllobora vigintimaculata, the twenty-spotted lady beetle, is a species of lady beetle in the family Coccinellidae. It is found in North America. P. vigintimaculata is about 1.75-3.0 mm in length and has 4-5 distinctive dark spots on the pronotum in an "M" shape. The elytron have dark, orange or bicolored spots on a white background. Although sometimes confused with the Fourteen-Spotted Lady Beetle (Propylea quatuordecimpunctata) and the Asian Lady Beetle (Harmonia axyridis), its unique pattern helps to distinguish it from other Lady Beetle species found in North America. In a laboratory setting, it was found that P. vigintimaculata taedata, a subspecies of P. vigintimaculata, undergoes four larval instars, ecdysis and then pupation. The timing of life cycle was also found to vary according to rearing conditions. It was noted in the study that the first instar larvae had a white oval colored body with small hairs projecting from the thorax. the larvae of the second instar had a stripe and a much darker color that gradually turned lighter with each subsequent instar. Additionally, the larvae gradually grew larger each instar. During the end of the fourth instar, the larvae attached itself to a leaf or a petiole in order to molt. Pupa emerged with wing pads as well as black spots. When eggs were deposited in 20°C it took about 32 days for adults to emerge. Under conditions of 25°C egg deposition to adult emergence took about 20 days. It has been proposed that P. vigintimaculata could potentially be used in place of fungicides as a biological control. This is because of its ability to utilize olfactory cues to seek out and feed on plants infected with powdery mildew which is an agriculturally significant plant parasite. This could help solve problems associated with current control methods like resistance, effect on non target plants, and worker's safety. However, arthropod consumption of mildew and its potential for disease control is understudied. Some important considerations involved insect and mildew density, ability to locate food as well as seasonality of feeding. The fungal parasite Hesperomyces virescens Thaxter has been known to infect P. vigintimaculata. The level of harm that the parasite causes to its host is still unclear because research on the topic has unveiled conflicting results.