# Comparative Study of Natural Fibres to Improve Insulation in Wooden Beehives Using Sensor Networks
## 1 Introduction  
The honey bee (_Apis mellifera_ [PERSON], 1758) is one of the most important organisms of the world due to its contribution to 75% of the pollination of vegetable crops, 35% of which depend directly on this mechanism, along with other pollinators [1]. The monetary value of this ecosystem service has been estimated at 351 billion $ (USD) per year [2]. In addition, 90% of wild plants have generalist animal pollination strategies [3]; therefore, the honeybee directly contributes to maintaining the biodiversity of flora. However, the honey bee is also one of the species most impacted by global change, being seriously affected by harmful agrochemicals [4] and the appearance of invasive species such as _Varrao destructor_ [PERSON], 2000 [5] or _Vespa velutina_ [PERSON], 1836 [6], and global warming [7; 8; 9; 10; 11], among other factors. The development of the beekeeping sector has standardised the internal dimensions of the hives to a regular frame size and are mainly made of softwoods, pine, and spruce in the majority [12; 13]. The most common beehives have movable frames [14], and there are several variants, such as Langstroth, Dadant, and Layens, depending on their dimensions and/or the position of their modules. The Langstroth hive, created in 1852, is the most widely used [15]. Wood has established itself as the most commonly used material for beekeeping due to its good mechanical properties, stability, ease of mechanisation, affordability, and satisfactory insulation properties. However, there are additional organic materials, such as cork or wood fibre panels, that could offer superior insulation properties. In recent decades, hives made of synthetic materials such as polystyrene and polyurethane have been developed and tested, yielding better results in cold climates [16; 17; 18]. However, the use of these synthetic materials is not always satisfactory due to their fragility and excessive impermeability and because they cannot be used for organic production due to European legislation. In contrast, conventional wooden hives do not exhibit these drawbacks. Historically, the construction of hives has been influenced by the availability of suitable materials, as noted by [19]. These materials ranged from terrestrial ones, such as sun-dried mud and baked clay, to plant-based materials, like hollow logs, cork bark, woven cylinders, splint stems, and wooden boards. In Mediterranean areas, cork bark cylinders were commonly used. Known for its superior insulating properties compared to wood, cork has traditionally played a significant role in hive construction. Although cork was one of the first materials used to make hives along with baked clay, wicker, or hollow logs [20], few publications are found with hives exploiting the incorporation of such natural fibre insulations in modern designs. [PERSON] et al. [16] analysed wooden hives with anagglomerated cork through field work in Sardinia (Italy) and evaluated the interior temperature thermoregulation of wooden hives and hives incorporating 3 cm of this natural fibre inside, achieving a more regular daily temperature pattern. Whereas there are research works that have analysed the interior temperature of the hive comparing wooden and plastic hives in field trials [16; 17; 18], there are hardly any results and investigations of standardised laboratory trials incorporating and comparing different natural fibres. Regarding polystyrene hives, they present higher thermal insulation compared to conventional ones but with significant disadvantages in relation to their higher price [21], lower durability [22], lower sustainability [12] and their prohibition for organic production [23]. Additionally, hives that are overly insulated from the external environment may encounter issues with internal overheating, which cannot always be efficiently mitigated by the bees' natural regulatory behaviours [24]. Research has also been carried out on the development of new materials, such as ferrocement [25], cement-vermiculite mortar [26; 27], or reinforced clay [28].