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Morphology

It is difficult to use morphological criteria for distinguishing the three Chrysoperla (C. carnea, C. kolthoffi, C.lucasina). However, keys for recognizing adults do exist (Çaldumbide C., Faessel L., Travers M., Rat-Morris E., 2001 - Les chrysopes communes, auxiliaires polyvalents. Phytoma. La défense des végétaux, 540, 14-19)

Adult: wingspan 23-30 mm, body (and wing veins) green with a thin straw-yellow dorsal stripe on thorax and abdomen. The overwintering individuals under diapause take on a yellowish to reddish brown hue.

Eggs: green, supported by a long flexible peduncle, laid individually, generally on underside of leaves.

Larvae: from 2 mm at first stage (newly hatched) to 7-8 mm at third stage. Yellowish grey, with body fusiform; tubercles topped with well developed hairs on sides of thoracic and abdominal segments. Mouthparts longer than head, evenly arcuate.

Biology

The adults are active throughout the night, from sunset to sunrise, from spring to autumn. They are not predators. They feed on nectar, sugary liquid substances and honeydew from aphids, Psylla and Coccoidea. In spring they feed on pollen.

The females can reach high levels of fecundity, but that depends on the quality and quantity of food available; on average they can lay more than 20 eggs per day. Depending on the temperature, the eggs hatch after 4-10 days. The larvae are highly active predators and strongly polyphagous. The larva catches its prey by deploying its hooks, making any resistance or escape impossible. It injects venom followed by a highly enzyme-rich saliva. The final action is to suck out all the lysed tissues from the prey’s body. To complete its growth, a larva consumes 200-500 aphids. At the end of its development (8-18 days), it closes itself in a silky white cocoon of 3-4 mm diameter. Its metamorphosis is achieved in this cocoon and the emergence of the nymph which will give rise to the adult then follows.

The full cycle takes 22-60 days. There are two to three successive generations. In the autumn, when the photoperiod shortens and the temperature falls, the adults from the latest generations gather together under various shelters (piles of leaves, dark sheds and other buildings). They then change color and are able to withstand winter by undergoing diapause.

In spring, the adult renews with its green livery and its activity. It reproduces more or less early depending on weather conditions and the availability of food.

Habitat

Among the seven species of Chrysoperla known in western Europe, three of them are grouped together under ‘common green lacewing’, the common name, and occur in the crops. These twin species, difficult to separate by means of morphological criteria, are distinguished by their ecological and biogeographical demands:

Chrysoperla carnea is found everywhere in France where it is often however not abundant and assonated with the tree layer.

Chrysoperla kolthoffi is more common in the west and north than in the south-east and mainly present in the herbaceous layer.

Chysoperla lucasina is characteristic of the Mediterranean region where it often occurs in the herbaceous layer.