The thesis aims to optimize the methods of laboratory culture and to fill in the gaps in knowledge of D. virgifera virgifera ecophysiology. The experiments on embryology and development proved that the diapause of D. virgifera virgifera is of obligatory type and can be terminated by exposure to long-day conditions (20:4; photo : scotophase) and constant temperature of 25 °C. Approximately 10% of eggs completed the development to adults within 4 months. Besides numerous other environmental conditions that are discussed, temperature seems to be a key factor influencing longevity in this pest. Higher temperature of 25 °C prolonged survival by more than 20 days in 2015, compared to 22 °C in 2014.

Transgenesis of silkworms has great potential for the development of silk with new properties as well as for the preparation of recombinant proteins for the use in biomedicine. Zabelina et al. (2015a) showed that transgenesis of parthenogenetic silkworms facilitates the selection and maintenance of transgenic homozygotes with stabile transgene insertions. However, the efficiency of transgenesis was less than 2 % compared to 60 % in the standard, non-parthenogenetic silkworms. The purpose of the present research was to explore the cause of this difference. Since transgenesis is normally performed at 25 °C but in the parthenogenetic silkworms at 15 °C (3 days incubation at this temperature is part of the protocol for the induction of parthenogenetic development), we assumed that the eggs incubated at 15 °C might have been injected with the DNA construct at unsuitable time. The work was therefore focused on the rate of embryogenesis at 15 °C in the eggs treated in different ways. Intensive cleavage of the control eggs (strain K23) was observed at 12 h after oviposition at 25 °C and between 24 and 36 h at 15 °C. The transgenesis of parthenogenetic silkworms is also complicated by the embryonic diapause. In the current work, diapause was suppressed by implanting PK1 ovaries into the non-parthenogenetic male hosts K23. Parthenogenetic development was activated by the heat shock in the chorionated eggs dissected from the implants. No cleavage was detected at 12 h after the acti-vation and nearly complete blastoderm was found at 48 h. In respect to the course of cleavage at 15 °C, transgene injection 24 h after the activating heat shock can be recommended. The eggs from endogenous ovaries of the K23 females, which also contained the implants of the PK1 ovaries, acquired partial capacity of parthenogenesis. Low rate of embryogenesis was also found in the transgenic clone VTG1. Current results suggest that more research is needed to understand and possibly explore differences in the rate of silkworms exposed to different treatments.

The thesis describes the development and survival of immature Ips typographus specimens at low temperatures under laboratory and field conditions. Further, the focus was identifying and characterizing the digestive enzymes present in the gut of adult I. typographus, their location in the gut and enzymatic fluctuation over a full calendar year, with a specific focus on digestion of cellulose.

The hypothesis that experimental manipulations increasing life span correlate to reduced physical activity and reduced molecular oxidative damage was tested. We used three longevity phenotypes of males and females of Pyrrhocoris apterus, diapause insects, reproductive insects and insect with ablation of the corpus allatum, an endocrine gland producing juvenile hormone. Protein carbonyl content in thoracic muscles was used as an index of molecular oxidative modification.

Current models state that insect peripheral oscillators are directly responsive to light, while mammalian peripheral clock genes are coordinated by a master clock in the brain via intermediate factors, possibly hormonal. We show that the expression levels of two circadian clock genes, period (per) and Par Domain Protein 1 (Pdp1) in the peripheral tisue of an insect model species are inversely affected by contrasting photoperiods. The effect of photoperiod on per and Pdp1 mRNA levels was found to be mediated by the juvenile hormone. Our results provide the first experimental evidence for hormonal regulation of circadian clock gene expression in insects.

The thesis deals with characterisation and changes of energetic status in the spruce bark beetle, Ips typographus, during pre-diapause, diapause and post-diapause quiescence.

Diapause is often an adaptation for survival during periods of harsh environmental conditions. Some diapausing stages do not terminate the dormancy once the favourable conditions are restored. Such prolonged diapause may be enforced by environment if a diapausing stage cannot be reached by the cues inducing termination of dormancy. However, it may also be an advantageous bet-hedging strategy to allow only a fraction of dormant stages produced in any given season to hatch the next time conditions become favourable. I tested whether such strategy can be observed in hatching patterns of dormant eggs of Daphnia obtusa - a cladoceran occurring in small Central European temporary waters. I investigated the influence of intensity of illumination on hatching success, and effect of isolating the eggs encased in ephippia from the sediment. Fraction of eggs terminating diapause, fraction of embryos successfully leaving the egg membranes, and timing of the response were assessed at 15 ˚C under four intensities of illumination (100% = 35µmol.m2 .s-1 , 75%, 50%, 25%; photoperiod 12h light: 12h dark) and in complete darkness for 21 days. My results support previous suggestions that there is no genetically-fixed bet-hedging strategy in D. obtusa. I observed high proportion of eggs which terminated diapause in all...

Recently, the cold resistance becomes a common topic in scientific articles. If we focus on order Heteroptera, we can find a lot of studies dealing with the cold resistance or with the supercooling point (SCP) and also with the factors that influence them. According to the general rule, the acclimation at low temperatures increases the cold resistance. Therefore, the main goal of this thesis is to find out, whether the acclimation also increases the cold resistance of the water cricket Velia caprai Tamanini, 1947 (Veliidae), with the intention to measure SCP of the water crickets depending on the acclimation temperature and the length of exposure. Due to the high mortality (the 284 individuals remained alive of total 1300) and due to the technical difficulties in measuring of SCP (measured only 36 individuals) it was necessary to modify the original goal of the thesis. The new goal was to test the influence of acclimation (during one month vs. one week) and the influence of different temperatures (0°C, 5°C, 10°C) on SCP of V. caprai. The individuals used for this measurement were collected during the year 2010 and in March 2011. The results of this thesis did not confirm the hypothesis that the acclimation at low temperatures increases the cold resistance. The individuals who were acclimated at a higher temperature have the values of SCP demonstrably lower than the individuals who were acclimated at low temperatures. The individuals who overwinter for the first time have arguably higher cold resistance than the individuals who overwinter for the second time. Probable cause of these results is the fact that the water cricket V. caprai does not start with diapause in the fall but it overwinters in quiescence.

Trade-off between reproduction and longevity is a widely accepted fact, yet proximate mechanisms are scarcely understood. In this work I tested differences in lifespan between diapause and non-diapause males of a model insect, the linden bug Pyrrhocoris apterus. Also the role of juvenile hormone in regulation of longevity and immunity (measured by relative phenoloxidase activity) was assessed. In addition to that, I examined if juvenile hormone is the mediator of reduction in longevity induced by mating.