Male dimorphism in insects is often accompanied by alternative mating tactics, which may, together with morphological traits, determine fitness of the different male morphs. Fitness consequences of male head horn size, male-male competition and male nest-staying behaviour were experimentally assessed in Copris acutidens, in which major and minor males can co-occur in nests. Possible differences in their reproductive behaviour and breeding success were assayed in a breeding experiment, in which females were paired with one major male, one minor male, or a pair of major and minor males. The advantage of major males staying in a nest along with a rival male is that major males are reproductively more successful than minor males in this species. The weight of dung transported into nests was significantly less in rearing containers containing two males than in those with a single male of either morph, although it did not differ between major and minor males when kept alone. The results indicate that the presence of a rival male negatively affects male provisioning due to interference from rival males. In contrast, in the present study, an increased incidence of male nest-staying behaviour was recorded in the two- male and one minor male treatment than in the one major male treatment. These results indicate that because of the risk of sperm competition, major males stay longer in nests if a rival male is present. Furthermore, minor males (which are subject to a higher risk of sperm competition) stay longer than major males in nests without a rival male. In other words, the present study revealed an alternative behaviour during the post-copulatory stage associated with horn dimorphism and the presence or absence of a rival male., Mayumi Akamine., and Obsahuje bibliografii
The ongoing process of climate change will result in higher temperatures during winter and therefore might increase the survival of overwintering invertebrates. However, the process may also lead to a reduction in snow cover and expose overwintering invertebrates to lower temperatures, which could result in higher mortality. During a field experiment, I investigated the effects of a reduction in snow cover on the survival of the ant Temnothorax crassispinus, which overwinters in nests located on the ground. Ant colonies differed in the survival rate of the workers in the experimental (from which snow cover was removed) and control group. In the control group, the survival rate was unrelated to colony size. However, in the experimental group, from which snow was removed after each heavy snowfall, worker survival was lower in small colonies. Such colony size related mortality may affect the fusion of colonies before winter. and Sławomir Mitrus.
Sjezdy různých spolků, organizací či politických stran tradičně nebývají považovány za zvláště vzrušující události. Často se konají především proto, že je to tak napsáno ve stanovách - sjezd bývá nejvyšším "orgánem" spolku, který směruje vývoj na období do dalšího sjezdu. Tím spíše by se dala očekávat nezáživnost takové akce u spolku, který má v názvu matematiku a fyziku a vyčpělé slovo jednota. Sjedou se tam nejspíše postarší pánové a několik málo dam a vše jednotně odkývají prošedivělými kšticemi. Bylo tomu tak i letos v Ostravě na 19. sjezdu JČMF? and Jan Valenta.
The rock architecture that forms part of the folk architecture has up to now been only inadequately studied. The present study is based primarily on the field researches that have been realized ince the 1950s by the Ethnological Institute of the Czech Academy of Sciences (up to the year 1999, Institute for Ethnography and Folklore Studes of the Czech Academy of Sciences), researches that cannot be thought of without mentioning the name of Emanuel Baláš. The author of the present study himself realized the researches in the second half of the 1990s. The study aims to present, in historical perspective, the special type of primarily provisional dwellings that were being hollowed out primarily in the sandstone rocks. Beside the living quarters, the attention is dedicated also to other types–for example, to the out-buildings (such as barns, cellars) and technical buildings (water mills, blacksmith shops, drying-rooms) that are found in greatest number in the regions of Mělník, Mladá Boleslav, Děčín, Česká Lípa and Semily. According to the datation, the majority of the rock dwellings had been excavated since the second half of the eighteenth century and especially during the whole nineteenth century. But it is beyond doubt that such objects had existed also before, probably already in the Middle Ages, when they had especially the function of temporary refuges. The making of a rock dwelling was in the majority of the cases conditioned by the social status of the „builders“ that belonged among the poor classes. This was especially the case of the local agriculture workers (for example in the region of Mělník) and also of the seasonal workers from Slovakia that were coming especially after the founding of Czechoslovakia. There are many diferences in the disposition, extent and arrangement of the rock dwellings, even though from the point of view of typology this dwelling stems from the three-part chamber house. The incomplete character of the rock dwelling that often was reduced to a hall with a room was caused on the one hand by the economic situation o f the owners, but primarily by the natural conditions (the shape and size of the sandstone massive). The process of the rapid extinguishment of the rock dwellings started after the year 1945 when many of their inhabitants moved out during the settlement of the frontier regions. Minor part of the objects has up to now been used as barns or cellars.