a-precise-autonomous-system-for-detection-insect-emergence

A Precise and Autonomous System for the Detection of Insect Emergence Patterns

Existing systems to measure insect emergence patterns have limitations; they are only partially automated and are limited in the maximum number of ...

North Dakota State University

Arizona State University

The alfalfa leafcutting bee, Megachile rotundata (F.), is a solitary, cavity-nesting bee and is the primary pollinator for alfalfa seed production. Bee management practices include cold storage during the prepupal stage. Fluctuating thermal regimes during cold storage increases survival of cold storage and allows a doubling of the cold storage period with no decrease in survival. However, survival, characterized as successful adult emergence, is not qualitative. In this study, we determined whether extended storage affects adult bee respiration or flight physiology. We overwintered bees for a single winter (current management protocol) or for 12 mo longer (extended storage). We used resting and tethered flight metabolic rates and resting critical PO2 (the oxygen partial pressure below which metabolism can no longer be sustained) as indices of adult bee quality. We found no significant differences in body mass, resting or flight metabolic rates, or critical PO2 between the two groups. Together these data indicate that extended storage of M. rotundata produces bees of similar respiratory capacity and flight ability. These findings could increase the use of M. rotundata as an alternative pollinator, allowing for extended storage to time adult emergence with early blooming crops.

Effects of extended prepupal storage duration on adult flight physiology of the alfalfa leafcutting bee (Hymenoptera: Megachilidae).

Metamorphosis is an important developmental stage for holometabolous insects, during which adult morphology and physiology are established. Proper development relies on optimal body temperatures, and natural ambient temperature (Ta) fluctuations, especially in spring or in northern latitudes, could result in interruptions to development. It is unclear how low-Ta exposure may affect insects that are actively developing. To understand how suboptimal Ta may affect metamorphosing insects, we used the alfalfa leafcutting bee, Megachile rotundata (Fabricius), a solitary, cavity-nesting bee that spends its juvenile and pupal stages within a brood cell. We characterized suites of physiological traits, rather than just using a singular parameter to determine effects of sublethal Ta stress. Metamorphosing M. rotundata were exposed to either constant or fluctuating low-Ta stress and compared to control bees allowed to develop normally. All bees survived and emerged as adults, but the constant low-Ta-stressed bees were affected most severely. Male constant low-Ta-stressed bees had decreased flight performance (lower metabolic rate, shorter flight bouts, decreased wing length), suggesting that the stress altered muscular or neurological development. Constant low-Ta-stressed bees also had altered activity levels, providing more support for the hypothesis that low-Ta stress causes long-term neurological defects. Exposure to fluctuating low Ta also delayed development time for both sexes; males had decreased adult life span, and both sexes had shortened wings. Together, these results provide evidence for a critical developmental window during metamorphosis and suggest that there may be severe implications for bees in the wild that are exposed to low-Ta stressors. 

Exposure to Suboptimal Temperatures during Metamorphosis Reveals a Critical Developmental Window in the Solitary Bee, Megachile rotundata.

Photoperiod is considered the universal zeitgeber, regulating physiological processes in numerous animals. However, for animals in light-restricted habitats (e.g. burrows or cavities), thermoperiod may be a more important cue. Our study tested this hypothesis in the alfalfa leafcutting bee, , which nests in cavities and undergoes development within a brood cell. We assessed the role of environmental cues (thermoperiod and photoperiod) on the process of adult emergence by examining: (1) whether those cues direct circadian rhythms, (2) which cue is more dominant and (3) how sensitive developing bees and emergence-ready adults are to cues. Although we found that 20% of light penetrates the brood cell, and bees respond to photoperiod by synchronizing emergence, thermoperiod is the dominant cue. When presented with a conflicting zeitgeber, bees entrained to the thermophase instead of the photophase. When temperature cues were removed, we observed free-running of emergence, indicating that underlying circadian mechanisms can be synchronized by daily fluctuations in temperature. We also found that emerging bees were highly sensitive to even small increases in temperature, entraining to a ramp speed of 0.33°C h The response and sensitivity to temperature cues suggest that  evolved a temperature-mediated clock to time emergence from light-restricted cavities.

Article	Year
Effects of extended prepupal storage duration on adult flight physiology of the alfalfa leafcutting bee (Hymenoptera: Megachilidae). Journal of economic entomology\| PubMed ID: 23865171	2013
Exposure to Suboptimal Temperatures during Metamorphosis Reveals a Critical Developmental Window in the Solitary Bee, Megachile rotundata. Physiological and biochemical zoology : PBZ\| PubMed ID: 26658248	2015
Cues for cavity nesters: investigating relevant zeitgebers for emerging leafcutting bees, . The Journal of experimental biology\| PubMed ID: 29636408	2018

Meghan M. Bennett

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