Les papiers sont des matériaux complexes qui sont constitués essentiellement de fibres cellulosiques. La nature des fibres, généralement issues de bois de feuillus ou de résineux, les opérations d'obtention et les traitements mécaniques, que celles-ci subissent, ont un impact très important sur les structures poreuses obtenues. La porosité des papiers peut ainsi varier de 1 % à 95 % selon les propriétés visées pour leur usage final. Leurs propriétés mécaniques vont en être affectées de manière très importante. En effet, leur résistance mécanique est liée à la qualité des fibres et des liaisons entre ces fibres. En outre, elle est très largement influencée par l'orientation des fibres et l'humidité. L'ensemble de ces facteurs engendre des problèmes de stabilité dimensionnelle (ou plutôt d'instabilité dimensionnelle) des papiers, qui peuvent s'avérer extrêmement problématiques lorsqu'ils sont transformés ou imprimés par exemple. En conséquence, il est important de mieux comprendre les modifications tant structurales que des propriétés mécaniques des papiers induites par des variations d'humidité. Des expériences ont été menées dans ce but sur un papierimpression-écriture. D'autres expériences, basées sur la microtomographie synchrotron, ont été effectuées à l'ESRF, "European Synchrotron Radiation Facility", afin de visualiser, à l'échelle microscopique, la structure fibreuse de ce papier et les évolutions de cette dernière lorsqu'il est placé dans un environnement où l'humidité relative varie.

Some aspects of the biology of Callosobruchus subinnotatus (Pic) were investigated at controlled conditions. Temperature and relative humidity were found to have effect on oviposition, development and longevity of adults. The best condition for oviposition was 30°C, 80% r.h. at which the mean number of eggs laid was 135.8 and the worst condition was 35°C, 50% r.h. at which 61.1 eggs were laid per female. Oviposition lasted very long at 25°C and was too short at 35°C. Relative humidity favoured oviposition at 30 and 35 but not at 25°C. The beetles were found to be positively phototactic as more eggs were laid at 12 hr light and 12 hr dark (105.1 eggs) and continuous light (98.6) than at continuous darkness (43.0).

Duration of development was shorter at 35°C than at other temperatures investigated. The shortest developmental period was at 35°C, 80 % r.h. (23.2 days) while longest was at 25°C, 50 % r.h. (42.6 days). While development was shorter at 35°C, more progenies were produced at 30°C and the rate of increase was better enhanced at 30°C. Adults were heavier when reared at lower temperatures and high humidities than at high temperatures and low humidities. Adults lived longer at lower temperatures and high humidities than at higher temperatures and lower humidities. The females were heavier and lived longer than the males.

Seasonal activity and environmental and hormonal regulation of development and diapause were studied in three different orders of tropical insects at Barro Colorado Island (9°N), Panama.

The seed bug, Jadera aeola, reproduces in the late dry season coincident with mass production of its food, seeds of Sapindaceae. Newly emerged adults enter diapause. Population density and food, but not photoperiod, appear to be involved in diapause regulation. Juvenile hormone analogue (JHA) stimulates sexual maturation in both sexes.

The fungus beetle, Stenotarsus rotundus, aggregates at the base of a palm tree where it remains in imaginal diapause for up to 10 months. In addition to daylength (Tanaka et al., 1987), humidity plays an important role in regulating diapause termination. Gonad and flight muscle development occur more rapidly at high humidity than at low humidity. Beetles treated with JHA initiate oocyte and flight muscle development but not testis development. 20-hydroxyecdysone has no effect on diapause termination.

Flesh flies (Sarcophagidae), when monitored with a meat-baited trap, show striking seasonal fluctuations in abundance. Yet, we found no evidence for diapause in three fly species reared in the laboratory under a range of photoperiod and temperature conditions.