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Pimelia is a genus of darkling beetle in the subfamily Pimeliinae.[1] Many Pimelia species individuals are very conspicuous as they cross the dunes. The epicuticle is highly reflective, with numerous tubercles randomly spaced on a fused elytral covering. Directly beneath, the sub-elytral cavity is approximately 1.0 mm in depth. When not traversing the desert surface, Pimelia burrows into the dune to escape predators or seek refuge from the hot desert sun.[3]

Introduction

Pimelia is a genus of darkling beetle in the subfamily Pimeliinae. Many Pimelia species are very conspicuous as they cross the dunes. Arid adaptations and behavioral modifications have allowed these beetles to survive in the inhospitable dune area. Locomotion in this difficult terrain is facilitated by numerous tarsal setae that allow for rapid tumbling behavior [2] which is used frequently to change direction or travel down the dune incline. Mating A univoltine genus, Pimelia in North Africa emerge in January to begin mating, synchronously with floral bloom. Normally Pimelia are detrivores, but during mating season it may cannibalize other adults, developing larvae, and eggs. This behavior may be due to need for extra nutrients or simply to eliminate competitors. Following behavior and mating take place on the slip face of the dune. After mating, the female digs a shallow hole and deposits a single egg, which closely resembles a grain of white rice. As the temperatures rise above fifty degrees Celsius, mating ceases as the adult population dies off. Immature stages remain below the surface until reaching maturity. During the following winter, the adults emerge and the cycle repeats itself.

Arid AdaptationsBold text

Arid adaptations allow Pimelia to survive and reproduce in the inhospitable dunes. However, in spite of the considerable effort to determine the factors affecting tenebrionid abundance in desert habitats there is no agreement on the relative importance of abiotic and biotic factors in the respect. Environmental factors influencing these adaptations are extremes of temperature and humidity, excessive radiant energy, low, irregular rainfall, long periods of drought, strong winds, a soil surface of loose sand, plus sparse and specialized vegetation. Several morphological adaptations allow Pimelia to survive in the desert including impermeable lipid layers of the epicuticle, fused sclerites, the sub-elytral cavity, and surface texture. Much of the success of tenebrionid beetles in desert habitats is due to the development of highly impermeable cuticles. Desert tenebrionids tend to have fused sclerites, a morphological adaptation minimizing water loss. In tenebrionid beetles, the spiracles open into a humid sub-elytral cavity rather than directly to the atmosphere thus reducing water vapor loss due to transpiration. The effect on water retention by intact elytral covers appears greater at 0% than at 97% relative humidity. The size of the cavity is not important. Transpiration increases if the elytra are removed emphasizing the importance of the epicuticle and sub-elytral cavity. Pimelia have tubercles on the surface of their elytra which scatter and reflect incident energy. This creates a boundary layer for the beetles. These adaptations, plus behavioral modifications allows Pimelia to live in the inhospitable desert dune areas.

Behavioral Modifications:

Burrowing is probably the most important behavior for heat regulation of Pimelia because it permits access to a broad range of ambient temperatures (Hamilton, 1975). Pimelia inhabit the soft dune areas, which allows them to burrow easily into the sand. The beetles dig into the side of the dune, and then the slip face of the dune collapses over them. Pimelia are diurnal beetles. During the hot desert days, they stay below the sand. They emerge in the early morning and late evening hours

Conclusion:

Pimelia species do not appear to have either a positive or negative impact on the areas they inhabit. Both morphological and behavioral adaptations have allowed them to survive excessive heat and drought. Many species have yet to be identified.