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Stabilizing mechanism in population of Malacosoma neustria testaceawas investigated in a central part of Japan based on eight year survey. Population fluctuation in each developmental stage in the experimental field was rather small, i.e., 5.9 times in egg and 85.0 times in female adult. Pupal weight negatively correlated with the densities of 5th instar larvae and prepupae (cocoons) and correlation coefficient was highly significant in females. Population density was stabilized by density-dependent dispersal of female moths in preovipositional period. Comparison between fecundity of emerged moths and that of actually oviposited ones in the experimental field suggested that density-dependent dispersal took place as the result of density-dependent size variation, i.e., small-sized female months have higher flying ability. This hypothesis was supported by the experiment in which flying ability of newly emerged female moth was measured. Similar stabilizing mechanism is expected to occur in semelparous or pro-ovigenic insects.

Stabilizing mechanism in population of Malacosoma neustria testaceawas investigated in a central part of Japan based on eight year survey. Population fluctuation in each developmental stage in the experimental field was rather small, i.e., 5.9 times in egg and 85.0 times in female adult. Pupal weight negatively correlated with the densities of 5th instar larvae and prepupae (cocoons) and correlation coefficient was highly significant in females. Population density was stabilized by density-dependent dispersal of female moths in preovipositional period. Comparison between fecundity of emerged moths and that of actually oviposited ones in the experimental field suggested that density-dependent dispersal took place as the result of density-dependent size variation, i. e., small-sized female moths have higher flying ability. This hypothesis was supported by the experiment in which flying ability of newly emerged female moth was measured. Similar stabilizing mechanism is expected to occur in semelparous or pro-ovigenic insects.

Intraspecies competition in a field population of Gregopimpla himalayensis(Hym.: Ichneumonidae) parasitic on the prepupae of Malacosoma neustria testacea(Lep.: Lasiocampidae) was investigated. The parasite oviposits the sufficient number of progeny (5 individuals/0.1 g dry weight of host) to exhaust a single host in a single attack. However, at the intensity less than 22–26 individuals/0.1 g d.w. of host, all individuals can emerge, i.e. density-dependent mortality does not occur. Within this range of intensity, survival of parasite larvae is guaranteed by diminution in body size and decreasing sex ratio. In contrast, total biomass of parasites showed a peak at 5 individuals/0.1 g d.w. of host at which a single host is exhausted. Above the intensity of 22–26, extraordinary minute individuals appeared and they died before maturation. If intraspecies competition play a role in regulation of G. himalayensispopulation in the field, the process is usually not through density-dependent mortality but through decreasing reproductive rate caused by decrease in the sex ratio, adult longevity and fecundity.

Summary: Some preliminary experiments with E 58 powder, derived from the strain E 58 ofBacillus thuringiensis were done with tent caterpillars (Malacosoma neustria L.). Sprays with 0,25 and 0,5% powder gave 80–90% mortality after 10 to 13 days of the second, third and fourth larval stages. These results were obtained after feeding with sprayed food, less effect was obtained by spraying the caterpillars only. The same effect, however, with a 0,5% spray only, was found in an outdoor experiment in large cages round about small apple trees. The main practical importance of these experiments follows from the fact that the used preparate proved to be highly specific, i. e. toxic to some caterpillars, however, non-toxic to other beings.

Summary: Two types of larvae ofMalacosoma neustria (L.) different in their behaviour as well as in their activity, produce also layers of hemocytes of different thickness after parasitization by the tachinidMericia ampelus wilk. A nuclear polyhedrosis that occurred simultaneously killed both larval types at different speed. The possibility is discussed that the quality of the hemocyte reaction to parasitization depends not only directly on the larval type, but also indirectly through the polyhedrosis.

The crystalline material covering the cocoon of Malacosoma neustria testacea(Lasiocampidae, Lepidoptera) was analyzed physically and chemically. The mean component was identified as calcium oxalate monohydrate, and the crystals were found to be whewellite in form.

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This paper reviews the studies and research on climate change impacts on the forest ecosystems in Northeast China. The results show that in the context of global and regional warming, the growing season of coniferous forests has been increasing at an average rate of 3.9 d per decade. Regional warming favors the growth of temperate broad-leaved forests and has a detrimental effect on the growth of boreal coniferous forests. Over the past hundred years, the forest edge of the cool temperate zone in the southern Daxing’anling region has retreated 140 km northward. From 1896 to 1986, the northern boundary of broad-leaved forests in Heilongjiang province has extended northwestward about 290 km. Future climatic changes (until 2060) may lead to the northern deciduous needle forests moving out of China’s territory altogether. The occurrence cycles of pests and diseases have shortened; their distribution ranges have expanded. The life cycle of tent caterpillars (Malacosoma neustria testaceaMotschulsky) has shortened from 14–15 years in the past to 8–10 years now. The pine caterpillar (Dendrolimus tabulaeformisTsai et Liu), which has spread within western Liaoning province and the nearby areas, can now be found in the north and west. Lightning fires in the Daxing’anling region have significantly increased since 1987, and August has become the month when lightning fires occur most frequently. Overall, the net primary productivity (NPP) of forest in Northeast China has increased. The NPP in 1981 was around 0.27 Pg C, and increased to approximately 0.40 Pg C in 2002. With the current climate, the broad-leaved Korean pine forest ecosystem acts as a carbon sink, with a carbon sink capacity of 2.7 Mg C hm–2. Although the carbon sink capacity of the forest ecosystems in Northeast China has been weakened since 2003, the total carbon absorption will still increase. The forest ecosystems in Northeast China are likely to remain a significant carbon sink, and will play a positive role in the mitigation of climate change.

Chemical trail marking and following by gregarious caterpillars,Malacosoma neustria L. (Lepidoptera: Lasiocampidae), was studied in the laboratory. As in other species ofMalacosoma, larvae deposit a trail pheromone from a sternal secretory site when searching the host for food. Larvae in the vanguard of foraging columns establish chemical trails as they explore new territory. Marking behavior diminishes as successive unfed foragers utilize the trail. These exploratory trails are subsequently overmarked by fed larvae returning to the tent. Other foragers follow the trails of fed larvae in preference to trails of unfed larvae. Thus, like the eastern tent caterpillar,M. americanum, successful foragers ofM. neustria recruit colony-mates to feeding sites. The chemical activity of both recruitment and exploratory trails degrades slowly, suggesting that the trail pheromone ofM. neustria is a nonvolatile substance. Caterpillars ofM. neustria readily follow the nonvolatile trail pheromone which has been identified fromM. americanum, 5ß-cholestane-3,24-dione.

Summary: The total forest area of Spain amounts to 26.5 Mill. hect. but only 12 Mill. hect. are stocked; 7 Mill. hect. by broad-leaved forest and 5 Mill. hect. by coniferous forest. The effective percentage of wooded land amounts, for the time being, to only 24.2 per cent. Between 1940 and 1945 1.8 Mill. hect. were forested with mainly 6 species of pine.About 80 per cent of the most important forest pests of Spain which belong to the most destructive enemies of the forest, are also to be found in central Europe. The most serious pests in stands of pine species are:Thaumetopoea pityocampa Schiff.,Lymantria monacha L. (onP. silvestris only),Diprion pini L., andNeodiprion sertifer Geoffr. The area attacked byTh. pityocampa, after the most recent evaluation, amounts to 1,750,000 hect., 600,000 of which exhibit serious damage of frass. The yearly loss of increment caused byTh. pityocampa is estimated upon 175,000 cubic metres volume and represents a value of 1.7 Mill. dollars. In reforestations of pine,Pissodes notatus F.,Blastophagus piniperda L., andRhyacionia buoliana Schiff., become harmful. As seed pests,Pissodes validirostris Gyll. andDioryctria mendacella Stgr. are economocally important, destroying the desired fruits ofPinus pinea L. or preventing their ripening. In contrast to the large number of pine pests that of other coniferous tree species play a little role. For silver fir, however, a serious pest arose by the regrettable introduction ofAdelges (Dreyfusia) nsslini C. B. into the Pyrenees;Pristiphoia erichsonii Htg., too, has to be considered a potential pest for the extended young crops of larch. It is remarkable that the possible Adelgids of larch withSacchiphantes viridis Ratz.,Adelges laricis Vall., andCholodkovskya viridana Chol. are complete although their host is not autochthonous in the Pyrenees.S. abietis L. was also recorded. Among the pests of broad-leaved trees, these of the oaks, especially ofQuercus ilex L. andQ. suber L, have the greatest importance, led on byTortrix viridana L.,Lymantria dispar L.,Malacosoma neustria L.,Catocala nymphagoga Esp., andC. (Ephesia) nymphaea Esp.T. viridana and its accompanying species formerly prevented the development on a large area, the “mast” ofQ. ilex which forms in many provinces the basic nutrition in comprehensive swine-breeding. Before an intensive chemical control was set up, yearly losses in swine mast amounted to 17 Mill. dollars. In poplar plantations serious damages are caused byCryptorrhynchus lapathi L.,Paranthrene tabaniformis Rott,Saperda carcharias L., andMelanophila picta Pall. The total yearly damage caused by forest pests in Spain amounts to approximately, 33 Mill. dollars.In Spain all duties of forest protection are managed by a central Institute the “Servicio de Plagas Forestales, Madrid”. The strong point of activities in forest protection lies so far in chemical control of forest pests. Between 1953 and 1965, 2,972,919 hect. of forests endangered by forest insects, were treated; 2,338,613 hect. of which were treated againstT. viridana. The control ofTh. pityocampa is well organised, methodically original and effective. Basic research in biological and integrated control is practised.