The husbandry methods detailed here provide a straightforward, reproducible framework for maintaining laboratory populations of C. morosus. Although C. morosus has long been kept in laboratories or as domestic pets, laboratory research husbandry protocols have varied across studies6,9,10,11,12. Ensuring consistent environmental conditions and feeding practices is important for making C. morosus a reliable laboratory model organism for developmental, physiological, and evolutionary research.
Developmental timing in C. morosus relative to other model insects
Compared to holometabolous insects such as the fruit fly Drosophila melanogaster, C. morosus exhibits slower developmental rates and a more prolonged juvenile phase. Whereas D. melanogaster completes embryogenesis in ~24 h and reaches reproductive maturity within 10–12 days at 25 °C13, under our rearing conditions, C. morosus requires 74–80 days for embryogenesis and approximately 135–139 days after hatching to reach reproductive maturity, corresponding to approximately 200 days from egg laying to reproductive maturity at 23 °C (data not shown). This extended timeline reflects fundamental physiological and evolutionary differences between hemimetabolous and holometabolous insects14,15 and is repeatedly found across the Phasmatodea16,17,18. While other hemimetabolous insects, such as the cricket Gryllus bimaculatus, complete embryogenesis and reach sexual maturity in a shorter timeframe (ten days and six weeks, respectively, at 29 °C19), the slower development of C. morosus provides a unique opportunity for reproducible research and detailed, longitudinal studies of embryogenesis and juvenile development.
Foliage source and feeding practices
In this protocol, we report using ivy (Hedera helix) as the primary food source for our C. morosus colony, with foliage collected from a consistent on-campus location year-round. While ivy may not be accessible to all laboratories, several alternative plant food sources have been reported to be suitable to maintain C. morosus colonies, including bramble (Rubus spp.), privet (Ligustrum spp.), firethorn (Pyracantha spp.), rose (Rosa spp.), hawthorn (Crataegus monogyna), oak (Quercus spp.), and hazel (Corylus spp.)20. One important consideration when using foliage collected from outside sources is that nutritional content is less controlled than in laboratory systems that rely on standardized diets (e.g., Drosophila melanogaster), potentially introducing nutritional variability. To help limit this, we used the same plant species from the same location across all seasons and provided foliage to all cages once per week during routine cage maintenance. Branches of ivy used for feeding typically had a mix of sprouting and mature leaves; we did not select branches for a specific leaf development stage. All leaves were washed prior to being added to cages. Our weekly replacement schedule, which removed all foliage and replaced it on the same day, was implemented for consistency and to manage the scale of the colony. Cut ivy foliage was kept in water-filled vessels within the cages to maintain hydration over the week. In most cases, the leaves remained in good condition for the full week, although occasional drying or depletion could occur, in which case we would replace the foliage earlier than 1 week.
Colony size, survival rates, and adult reproduction
Proper colony setup and careful management of population density were key to keeping the stocks healthy. Maintaining a maximum of approximately 500 hatchlings or 50 adults per 61 cm x 61 cm x 91.5 cm enclosure supported stable conditions, colony maintenance, and reproducible developmental observations.
Comparing average daily mortality with the number of founding adults in a cage (Figure 4A and Table 1) revealed no predictable relationship between these two parameters. Similarly, there was not a strong predictive relationship between the total number of founding adults and total egg production (Figure 4B, Table 1, and Table 2). Instead, cages with lower average daily adult mortality showed a mild tendency to have higher average daily egg output (Figure 4C). However, differences among cages suggest that egg production varied among adults (Table 1 and Table 2), which could mean that factors beyond adult survival contribute to fecundity patterns, and that individual females may also vary in how many eggs they lay each day.
Egg production in all monitored cages generally declined over the course of the experiment (Figure 2). Most cages had the highest daily egg-laying rates early in the reproductive period (first 50 days), after which production gradually tapered off (Figure 2). This pattern is consistent with our observation that individuals typically reach sexual maturity and begin laying eggs at approximately 135 days post-hatching, and that mortality begins approximately 90 days later (~225 days post hatching; data not shown).
Timing and dynamics of hatching
Across the monitored egg batches, most hatching occurred within a consistent 12-day period following the onset of emergence (Figure 3D). Similarly, there was no correlation between batch size and the timing of 90% hatch completion (Figure 3A), and most batches reached 90% hatch completion between days 10 and 14 after the first hatchling emerged (Figure 3B). This predictable hatching period is a useful feature of C. morosus colony management because it allows hatchlings to be grouped into cohorts of similar age, improving developmental staging and reducing experimental variability. Knowing when bulk hatching will occur also allows for better planning of enclosure turnover and resource allocation, including the timely preparation of enclosures, foliage, and tracking materials, which is especially important for large-scale or long-term studies. Although both sexual and parthenogenetic Phasmatodea species have been studied, we know of no evidence that reproductive mode alone drives differences in embryogenesis timing. Instead, variation in development has been reported as being species-specific and influenced by environmental conditions2.
Egg handling and substrate considerations
Our egg-handling method involves collecting eggs directly from the enclosure floor and incubating them in ventilated Petri dishes. This approach makes eggs easily observable, unlike cricket systems that collect eggs in substrates such as coconut fiber or cotton wicks21. The hard exochorion of C. morosus eggs provides protection during handling and against desiccation, enabling safe incubation in Petri dishes without additional substrate under our culture conditions. Taken together, these standardized procedures provide a structured approach for maintaining healthy C. morosus populations for reproducible developmental, behavioral, genetic, or physiological research. Consistent environmental controls (23 °C, 70% RH, 12:12 LD), regular enclosure maintenance, and predictable developmental timelines make C. morosus an accessible and low-cost model system. Importantly, unlike some cricket systems where crowding, cannibalism, or pathogen load can rapidly destabilize colonies22, C. morosus are easy to maintain, making them well-suited for large-scale experiments and studies spanning multiple generations. As C. morosus becomes more widely adopted as a hemimetabolous model species, the use of standardized methods should promote reproducibility and comparability across studies in multiple areas of insect biology.
Survival from hatching to adulthood
Survival from hatchling to adulthood in our study (~13%) is substantially lower than that reported by another quantitative study of C. morosus nymph survival under controlled laboratory conditions, in which 68% of individuals survived to adulthood under caloric restriction and up to 87% under ab libitum feeding23. We speculate that the lower survival we observed in our colony (~13%) relative to the previous report is due to differences in how the animals were reared, which in turn reflect the different goals of our culture and that of the previous study. Our protocol was designed to maintain large, continuously reproducing colonies, rather than to maximize survival of individual groups. Thus, we kept animals at relatively high densities, in contrast to the previous study, which raised isolated animals from egg to adulthood in individual cages23. We speculate that the high-density culture method we describe here may increase mortality compared with rearing in isolation, especially during early nymphal stages, when individuals may be more sensitive to crowding or competition. In our larger cages, variation in plant quality may also have played a role, compared with the individual rearing approach, which fed individuals discs of controlled size cut from plant leaves23. However, despite its comparatively lower survival rate, our colony consistently produced large numbers of eggs and remained stable over time (Figure 1, Figure 3, Table 1, and Table 2). This suggests that the approach we describe here is effective for maintaining a long-term laboratory culture.
Factors influencing survival and protocol limitations
Several factors in this protocol are likely to influence survival and should be carefully controlled. Population density is an important parameter, as overcrowding may reduce survival, particularly during early instar stages. Another parameter that influences survival is adequate hydration, especially during early instar stages. All procedures and timing described in the protocol are based on the specific environmental conditions used in this study. However, changes in humidity, temperature, airflow, or plant type may affect the frequency of water misting, how often foliage needs to be replaced, egg hatching time, and overall survival. For example, in drier culture conditions, more frequent water misting and plant replacement may be needed to maintain hydration. Different plant species may also influence feeding and development. These factors should be adjusted depending on the rearing conditions and experimental goals. For applications requiring high juvenile survival, individual tracking, or behavioral assays, lower starting densities may be preferable.