A new species of genus Rhinotorus Förster (Ichneumonidae, Ctenopelmatinae) parasitizing Pristiphora erichsonii (Hymenoptera, Tenthredinidae) and a key to Eastern Palaearctic species

A new species of Ctenopelmatinae, Rhinotorus nigrus Sheng, Li & Sun, sp. nov. reared from cocoons of Pristiphora erichsonii (Hartig) in Jilin Province, China, is described and illustrated. A key to Eastern Palaearctic species of Rhinotorus is provided.

A new species of genus Endasys Förster (Ichneumonidae, Cryptinae) parasitizing Pristiphora (Tenthredinidae) and a key to species from China

A new species of Cryptinae, Endasys pristiphorae Sheng, sp.n. reared from cocoons of the tenthredinid sawflies Pristiphora erichsonii (Hartig), P. xibei Wei & Xia and P. (Stauronematus) compresicornis (Hartig) in Ningxia, Shandong and Shan’xi, China, is described and illustrated. A key to species of Endasys known from China is provided.

Dynamics of eastern larch stands and its relationships with larch sawfly outbreaks in the northern Clay Belt of Quebec

Climate change, fires, and insects outbreaks can affect eastern larch (Larix laricina (Du Roi) K. Koch) stand dynamics. To determine which of these factors had the greatest influence on stand dynamics, we sampled four wetlands dominated by larch on the margin of Lake Duparquet in the northern Clay Belt of Quebec. The ages of seedlings, saplings, and trees were determined in twelve 400-m2 plots. Increment cores were taken at breast height to determine past disturbance episodes related, among others, to larch sawfly (Pristiphora erichsonii (Hartig)) activity. Stem analysis was conducted using larch and black spruce (Picea mariana (Mill.) BSP) for identification of post-disturbance releases in height growth. Analyses at the stand and cluster levels showed that larch age structures were characterized by many unsynchronized establishment periods. In addition, a seedlings bank not much older than 10 years characterized many plots. Two larch sawfly outbreak episodes (1895–1912 and 1955–1962) identified by tree-ring and stem analysis were associated with larch establishment. A smaller outbreak in the late 1970s could also have contributed to the initiation of establishment in one stand. Our results suggest that the length (severity) of an outbreak may be a critical factor in explaining the different patterns of establishment observed in these stands. During a severe outbreak, larch establishment may occur mainly from surviving stems (increased seed production), whereas during a mild outbreak, larch establishment may occur from increased survival of pre-established seedlings and saplings. Further studies on the distribution of gaps within larch stands may provide better information on the pattern of mortality (gap dynamics) during an outbreak and may help to better understand larch establishment in these stands.

RECENT OUTBREAK OF THE LARCH SAWFLY, PRISTIPHORA ERICHSONII (HARTIG), IN SUBARCTIC QUÉBEC

Larch sawfly oviposition activity as revealed by scarring of long shoots of eastern larch, Larix laricina (DuRoi) K. Koch, was measured at various locations in the high boreal forest and forest tundra in Québec in 1988 and 1989. The data show that larch sawfly is established up to the tree line, even on isolated larch growing under climatic conditions that are extreme for this tree. Frequency distributions of scarred shoots as a function of time suggest thai larch sawfly populations reached outbreak levels in the 1980s, with peak numbers in 1981 for the high boreal, and in 1985 for the subarctic regions sampled. Trends in long shoot production by larch trees started to fluctuate simultaneously with the sudden increase in larch sawfly populations along the Grande Rivière de la Baleine in 1984. In this region in 1985, the proportion of long shoots used by Pristiphora erichsonii averaged 20–35%, which may have limited further population increase. Although foliage reduction and branch mortality were observed, mortality of whole trees was not a general characteristic of this outbreak.