Larvae are white or yellowish, but after feeding for a day they begin to turn light purple or lavender. After emergence, larvae will immediately begin to feed either on the scale eggs sharing the space beneath the the armor.The larvae will continue to move from scale to scale feeding on males, females, and eggs, but will spend most of their time underneath a female armor. Larval development passes through three instars. The larvae feed for 9-10 days before entering a prepupal phase which lasts 2-3 days, during which time movement is slowed and feeding ceases.
Pupal chambers are often found at the junction of the vertical column of the leaf, leaf and leaflet. When larvae are not given access to scales they will form the pupal chamber with sand and other organic material, sometimes attaching to the leaf and sometimes dropping to the soil. The beetles remain in the pupal chamber for about 18 days before chewing an exit hole for emergence.
The preoviposition period lasts about 4 days with some females laying eggs as early as 2 days after emergence. Females generally lay 3 eggs per day and on average of 288 eggs in their lifetime. Adults begin feeding soon after emergence and can consume up to 4 scales per day, with females typically consuming more than the males. Adult females have an average lifespan of 110 days, while males average 89 days. With a total life cycle from egg to adult only taking about 40 days. There is a chance that 7-8 generations could be produced per year depending on conditions.
These predatory beetles have a long lifespan and can also be known to resist or protect themselves from pesticides. The larvae develop and feed under waxy covers that protect them from direct exposure to pesticides. Although, it is not suggested to use these predators in conjunction with pesticides.
While having the ability to persist at low scale densities, they also tend to stay on the infested tree or plant until the food source is exhausted, then leave and return when the scale population has increased.
The larvae will be hard to find. If a bright light is shone on a larvae it will immediately move underneath a scale armor or debris. Once disturbed the larvae will raise its head and body away form the leaf surface, arching the body into a C-shape while holding onto the surface with its lower body.This threat posture is similar to that used by the larvae when extracting themselves from old scale armor.
You can always try tapping branches while holding a white sheet of paper under the branches to try and catch the adult predators.
AdvisoriesGrowers and homeowners should follow proper sanitation practices in pruning infested plants. In many cases, the crawler stage of the scale pest can be spread from plant to plant by pruning equipment or by infested clippings that are not discarded properly. A good practice is to clean pruning equipment before moving to new plants and to destroy infested clippings to eliminate them as potential sources of further infestations.
Ants, if present, should be controlled. They will defend C. nipponicus from predators and parasites to protect their honeydew/excrement food! Use barrier products or boric acid products to control the ants.