The experiments in space with this species have been mainly focused on the impact of microgravity (µG) on cellular processes. Acheta domesticus was used as model species within the project “Crickets in Space” (CRISP) and the potential gravity sensitive neuronal system was studied during several years (see Horn et al., 2007). Eggs, different larval stages and adults flew within spacecraft for different time periods, not exceeding 16 days (Förster et al., 1999; Horn et al., 2001; 2002; 2003; 2007; Kirschnik et al., 2002; Kirschnick and Horn, 2006). In-flight fertilization (after 7 days of space flight) occurred in orbit; after landing, flight eggs hatched 1.5 days earlier than the ground controls (Kirschnick and Horn, 2006; Horn et al., 2007). Morphological features of sensory cells and neurons of the newborn larvae were rarely seen to be affected by µG (Horn et al., 2007). Crickets of four developmental stages (eggs, I-, IV-, and, VI-larval stage), that flew in space for 16 days, showed a low susceptibility in their behavioural response to µG. However, the position-sensitive interneurons (related to movement coordination) activity revealed a significant sensitivity (Horn et al., 2003). Overall, microgravity seemed to rarely affect the morphological features of sensory cells and neurons development while the physiology of the position sensitive neuro system was significantly affected and their sensitivity reduced (Kirschnik et al., 2002; Horn et al., 2001; 2002; 2003; 2007). A change was seen, after 13 days of space flight, when the crickets appeared to be capable of normalising the development of their multi-channel gravity sensory system to their new gravitational environment (Förster et al., 1999). Microgravity is an environmental factor known to induce muscular atrophy in different species (Leonard and Albury, 2015). During simulated µG by clinorotation, a significant loss in muscle mass and enzymatic function was found in individuals of the species from day 1. Therefore, the natural histolysis of flight muscle that occurs in the house cricket development appears to happen sooner (Leonard and Albury, 2015). In general, the responses seen in A. domesticus to gravity reduction are likely to be adaptations related to physiological modifications and permanent changes (Horn et al., 2007). Short term µG conditions have not been found to impact development of a stable nervous function, as readaptation took place in individuals (Horn et al., 2007).

Although T. molitor has been suggested as a food source for space travelers (Li et al., 2016; Jones, 2015), no experiments in orbit have involved this species. To elucidate the effects of low gravity on the larvae stage in the life cycle, mealworms were subject to a short duration experiment at approximately 0 G during parabolic flight. This treatment led to a 30% reduction of metamorphosed larvae (Davis, 1999), probably due to larvae dying.

Other tenebrionids have been used in space experiments, namely, the desert beetle (Trigonoscelis gigas Reitter, 1893), the red flour beetle (Tribolium castaneum Herbst, 1797), and the confused flour beetle (Tribolium confusum Du Val, 1863). The former one was used in several space flights and simulated gravity experiments to test if its activity rhythm and circadian functions were altered by µG (Alpatov, 1991; Alpatov et al., 1994; 1998; 2000; Hoban-Higgins et al., 1997; 2000; 2003). Both basic features of circadian rhythms and the expression of the clock responsible for these rhythms were found to be altered (Alpatov et al., 1994; Hoban-Higgins et al., 2003). In particular, the free-running period (i.e., animal is said to be free-running in an environment without time cues, the length of an animal’s day is determined by the period of its internal pacemaker) was significantly affected by both the µG and ambient light intensity, but with contrasting results: this period resulted in a longer time period according to Alpatov et al. (1998) and a shorter one in Hoban-Higgins et al. (2003).

The red flour beetle was used to study the occurrence of gravity-sensitive steps during oogenesis and embryogenesis. The results from two space flights of 6 and 10 days indicated that several aspects of the development and function of the reproductive system of females were not sensitive to microgravity (Bennett et al., 1994). In particular, μG did not affect the development of the female reproductive system, the viability of embryos, and inseminated females continued to lay fertile eggs, when back on land (i.e., there was no depletion of stored sperms) (Bennett et al., 1994).

For T. confusum, the experiments in µG (in orbit or simulated by fast-rotating clinorotation) suggested that embryogenesis was not gravity-sensitive, although some aspects of adult development could be (Cogoli, 1992; Bennett et al., 1994). The confused flour beetle successfully completed a full generation in space, although no precise quantitative data were obtained on mating competence and various aspects of development in this study (Miquel, 1984).

Only three experiments have been performed with A. mellifera (Nelson and Peterson 1982; Vandenberg et al., 1985; Smith et al. (2021). During space flights, the bee flights were very brief without wingbeat (resulting in floating) and without control of attitude in any body axis. The control of their orientations for landing and movements prior to a rest period on a surface were very difficult (Nelson and Peterson, 1982). The post flight eggs hatchability showed contrasting results. According to Vandenberg et al. (1985), the eggs laid by the queen of a mature hive sent in space for 7 days failed to hatch after the mission’s return. By contrast, according to Smith et al. (2021), a queen was able to lay viable eggs after a shorter space flight and all observed eggs hatched into healthy offspring in the experiment.

Other insects were used for space experiments. Another Apidae as the bumblebee (Bombus ignites) was studied in μG by parabolic flight, showing and altered flying behaviour (Yamashita et al., 2010). The lepidopteran velvet bean caterpillar moths (Anticarsia gemmatalis) and the dipteran common houseflies (Musca domestica) were studied by Nelson and Peterson (1982) in the same experiment with honeybees. In space conditions, moth flight activity was very uncontrolled and brief (less than 10 s), and the moths had some difficulty orienting themselves during landing. The uploaded moth pupae were able to successfully emergence to imago in space (Nelson and Peterson, 1982). Even the housefly flight activity was very brief (generally less than 1 s), but houseflies were capable of better controlling their pitch attitude, flight path, and landing process than moths and bees. From the preflight uploaded housefly pupae, the imago emerged successfully in space (Nelson and Peterson, 1982).

The hymenopteran pavement ants (Tetramorium caespitum) were studied to analyze how they performed collective search in µG (Countryman et al., 2015). Collective search is used by the ants to optimise the area covered by the group. In space conditions, the ants explored the surface less thoroughly with more convoluted routes, probably due to the difficulty in clinging to the surface. In fact, they often lost contact with the surface but showed a remarkable ability to regain it (Countryman et al., 2015). Between 2005–2010 the larvae of the chironomid Polypedilum vanderplanki Hinton, 1951 were utilized as a model organism in experiments on resistance of resting stages of invertebrates to space environment both inside and outside of ISS (Gusev et al., 2010a). The larvae in anhydrobiotic state survived after 18 months of direct exposure to outer space environments (Gusev et al., 2010b).

The stick insect Carausius morosus (Phasmatodea, Heteronemiidae) was used in different space missions as it was considered one of the classical models in developmental biology. Eggs at five different stages of development, representing different sensitivities to radiation and different capacities for regeneration, were tested. Eggs at five different stages flew for 7 days either at µG conditions or on the 1 G centrifuge to separate the effects of radiation and microgravity and to analyze the combined effects (Bücker et al., 1986). The early stages of development showed to be highly sensitive to radiations and to µG during development (e.g., µG reduced hatching rate). In some cases, the combined action of these factors amplified their negative effects and produce a high frequency of anormal larvae (Bücker et al., 1986). Eggs at different stages flew in other two missions for 9 and 13 days (Ushakov and Alpatov, 1992; Reitz et al., 1989; 1992). No significant changes in developmental time were detected although the hatching rate decreased, especially eggs with an age of 31 days (embryogenesis lasts 75–105 days) (Ushakov and Alpatov, 1992; Reitz et al., 1989; 1992). Six different ages of eggs further flew for 8 days (Reitz et al., 1995): a reduction of hatching rate was observed in agreement with previous studies, while morphological and developmental changes during embryo development were detected (in contrast with the previous missions), although some repair capacity seemed occur.

The insect most used in space experiments and the first animal survived in outer space (in a V-2 rocket in 1947; Beischer and Fregly, 1962) is the fruit fly Drosophila melanogaster. It represents a well-established spaceflight model organism: fruit flies have yielded significant information on the effects of microgravity in many different fields of physiology and behavioural and developmental sciences (for a review see Iyer et al., 2022). Overall, previous studies showed normal development of Drosophila melanogaster during flights, but evident structural and functional cardiac impairments, neurobehavioral deficits, suppression of immune system (with increase virulence for some pathogens; Gilbert et al., 2020), and alterations in gene expression profile were observed under spaceflight conditions (Iyer et al., 2022; Mhatre et al., 2022).

Drosophila melanogaster is the only insect for which it was tested the possibility to complete the life cycle and reproduction in space. Fruit flies were able to complete the life cycle (from zygote to mature adults) under space flight conditions, obtaining offsprings (Vernos et al., 1989; Ogneva et al., 2016; Marcu et al., 2011; Taylor et al., 2014). Size and number of eggs increased under microgravity conditions and life span decreased in males, but not in females (Marco et al., 1986; Vernos et al., 1989; Marthy, 2002). Still after 13 days of spaceflight, D. melanogaster maintained normal locomotor activity rhythm and sleep pattern (Ma et al., 2015), but circadian clock was affected. As the ability to keep a normal photoperiod may ease the effects of microgravity, a suitable photoperiod and lighting system (intensity, spectrum, and distribution) could offer powerful countermeasures for circadian and sleep disorders during spaces flights (Zhang et al., 2021).