A preliminary report on the study of larch leaf wasp

1 Distribution and harm

Larix gmelinii is mainly distributed in Heilongjiang and Jilin provinces. It is a dangerous pest in the leaves of Larix gmelinii, the damage period is from June to September, and it mainly harms the 10 ~ 30-year-old larch. The insect spreads quickly and does serious harm. The occurrence area of the third generation larvae from Hailin Forestry Bureau in 1985 to 1986 reached 150000 mu, of which 67000 mu were seriously damaged, the highest population density was 21000 trees, and the average population density was 6026 per plant. The peak period of larch larva damage after Yiteng is the peak growth season of larch, and the seriously damaged stand looks like burning a piece of yellow, which seriously inhibits the growth and development of larch.

(2) morphological characteristics of silk leaf wasp after Yiteng

2.1Adult: female has body length 8~9.5mm, head width 2~2.5mm, wingspan 18~18.5mm, male body length 5.5~7mm, head width 1.5~2mm, wingspan 11.5~12mm, brown and glossy, compound eyes black, antennae filamentous brown, small black spots on the head, and the color of males is heavier than that of females. The foreleg segment, middle leg segment, posterior leg segment and diametral segment, middle chest and the lower half of the lateral plate of the female were black, while the anterior, middle and posterior feet of the male were brown, and the anterior, middle and posterior thoracic dorsal plate, scutellum and middle thoracic lateral plate were black.

2.2 eggs: long oval, long 1.3~1.5mm, wide (middle diameter) 0.5~0.55mm, the first egg is milky white, after 6-7 days, it turns into a gray water-like transparent body, there is a small black spot in the egg, and the mouth is the compound eye of the unhatched larvae in the egg.

2.3larvae: the length of the newly hatched larvae is 2.5mm to 2.8mm, and the head width is 0.50~0.55mm. The mature larvae are 10~18mm in body length, 1.8~2.2mm in head width, milky white in body, black in head, 2 rows of black spots on the back, black on the first segment of the abdomen, two rows of black spots on the outside of the base of the abdominal foot, chewable mouthparts, well-developed chest feet, black toe hooks, and underdeveloped abdominal feet with toe hook white.

2.4pupae: the naked pupa has a long 6~9mm, a white body, an orange head, a reddish brown compound eye, a long oval cocoon, a dark brown cocoon, a female cocoon length 8~12mm, a wide 4~6mm, a female cocoon length 5~7mm, and a wide 3~5mm. The cocoon is divided into two layers of skin, the outer cocoon skin is soft filiform herbaceous, and the inner layer is tough horny.

3Biological characteristics

3.1 Life history: the worm has 2-3 generations a year, the first generation adult Eclosion period is mid-June, the second generation adult Eclosion time is from mid-July to late July, the third generation adult Eclosion time is from mid-August to late August, the mature larvae begin to go down the tree as cocoons to overwinter in mid-September, the larvae are divided into 5 instars, the cycle is about 15 days, the egg period is about 9 days, and the pupa period is about 8 days.

3.2 Life habits: the worm pupated from late May to early June following the overwintering of the pupa, emerged in mid-June, the male first emerged, followed by the female Eclosion, the adult bit a small hole at the top of the cocoon during Eclosion, and the newly emerged adult was weak, first crawling back and forth on the litter layer or grass, and then flying for a short distance, the male was more active and had strong flying ability. Generally, the female flies round and round from 0.5 to 1m above the ground, and the highest flight is about 2m. After Eclosion, the female climbs to the litter layer or to the obvious place under the forest. The males come into contact with each other around the flight, and the mating time is about 2min. 1 the female can mate with different males many times, and then fly to the back of the old leaves of the larch branches to lay eggs, and when laying eggs, the females climb on the back of the leaves. Hold the abdomen of the leaf and stick it to the back of the leaf to lay 1 egg, then move forward to lay another egg or climb to the back of other leaves to continue to lay eggs, and continue to lay eggs on the second day after laying on the same day. Care here after laying (for example, it fights with other insects and female worms of the same species at this time). The maximum number of eggs laid by the female is 77 and the lowest is 44, with an average of 59. The adult has no false death. The life span of the adult is 4-5 days without supplementation and about 10 days when replenished.

The hatching rate of the egg is about 95%. Before hatching, the egg changes from milky white to gray and transparent on the surface. During hatching, the larvae in the egg can be seen. During hatching, the egg gradually becomes transparent from white to transparent, and the head changes from 1 to 2. In the egg, with the substance in the egg, the egg shell is broken by the head arch when the active larvae hatch, the newly hatched larvae are white and transparent, and the compound eyes are black. The mouthparts are reddish brown, and the color of chest, toe, head and back darkens after half an hour. After 2min, the mesophyll of spawning leaves is eaten, and then moves downwards. The whole leaf can be eaten after the 2nd instar, and the 3rd instar begins to disperse the harm. The larvae are easy to feed on the old leaves with weak photosynthesis, and in special cases, they also feed on the new leaves. Each instar of larvae is 2-3 days. When peeling, the larvae peel from head to tail, the new peeling larvae are white, the markings on the posterior body of transparent 1min become darker, the head and feet are uniform and transparent, and the color of head and feet darkens after 50 minutes. When the larvae are alarmed, the tail swings back and forth.