A long time ago, when I was on field expeditions, I often saw a cocoon, oblong-shaped, mesh-like, hard to pinch, very strong, it was not easy to tear it, and I wondered what kind of animal cocoon this was, so strange. Later, I learned that this was the cocoon of the Ginkgo giant silkworm moth.
Ginkgo biloba silkworm moth is a very common insect in the Qinba Mountains, it feeds on the leaves of the plant by larvae, although the name only carries the ginkgo biloba plant, but its diet is very mixed, not only harming the ginkgo biloba, but also harming walnut, maple poplar, sumac, plum tree, persimmon tree, willow, cherry and dozens of other plants, when the occurrence can eat all the leaves of the whole tree, seriously affecting tree growth and fruit yield. At present, the ginkgo giant silkworm moth has attracted much attention mainly because it is an important pest of walnut, and walnut is the main economic tree species that has been vigorously promoted and planted in the Qinba Mountains for a long time.
The Ginkgo giant silkworm moth occurs once a year in the Qinba Mountains, and after the eggs overwinter, they hatch into larvae from late April to early May, and the newly hatched larvae feed in clusters on the back of the leaves and slowly disperse as they age. Larvae in different ages of appearance and morphology is relatively large, especially the body color from all black to the back of the body black, and then to the back of the body white, off-white, not easy to identify, from the perspective of the several ages I shot, the larvae have two obvious common features, one is that the body surface is covered with white long hairs, and the other is that the body side has obvious blue spots, this blue is more special, easy to identify.
From late June to early July, the old mature larvae begin to form cocoons between the host branches and leaves or in the shrub weeds, with the largest number of shrub weeds under the canopy, and the cocoons are often wrapped in leaves, which have good concealment. The cocoon of the Ginkgo giant silkworm moth is very special, the whole is oblong-oval, about 5 cm long, brown, hollowed out in a net, and the texture is relatively strong. The larva pupates inside the cocoon, and through the holes in the cocoon, the process of pupal pupalization and the morphology of the pupa can be clearly seen from the outside.
Pupae feather from mid-August to September. Adults are more likely to feather at night, and after feathering, they crawl out of one end of the cocoon, and then gradually extend their wings and become dry. The feathered empty cocoon, although discarded and unused, is still very strong and can be retained on the branches for a long time. The adult of the Ginkgo silkworm moth is larger, with a wingspan of 12-13 cm, dense hairs all over the body, an inconspicuous oval transparent spot in the middle of the forewing, an obvious eye-like spot on the hindwing, the difference between male and female is obvious, the male moth is smaller, the antennae are wider, dark brown, while the female moth is larger, the antennae are narrower, reddish brown. Adult insects have phototropism, once I happened to encounter an outbreak of ginkgo large silkworm moths, and at night under the lights, its adult insects flew in groups, and there were several steps on the road, and the number was very large.
■ Ronghai