Polymorphism in some nearctic halictine bees.

Area of Science:

• Entomology
• Ecology
• Evolutionary Biology

Background:

• Social insects exhibit significant size variation between castes, such as queens and workers.
• In Halictinae bees, size dimorphism is a key factor influencing reproductive roles and colony dynamics.
• Understanding the environmental factors driving this size variation is crucial for bee biology.

Purpose of the Study:

• To quantify the size difference between queens and workers in four common southern Ontario Halictinae species.
• To investigate the relationship between larval provisioning and the resulting adult bee size and caste determination.

Main Methods:

• Comparative analysis of adult queen and worker sizes across four Halictinae species.
• Measurement of larval provisions (in milligrams) for spring and summer broods.
• Correlation of provision amounts with observed adult size and caste.

Main Results:

• Average size difference between queens and workers ranged from 6% in Augochlorella striata to 15% in Evylaeus cinctipes.
• Spring larvae received an average of 33.9 mg of provisions, developing into smaller workers.
• Summer larvae consumed an average of 61.7 mg, developing into larger queens and males.

Conclusions:

• Larval nutrition is a primary determinant of caste and size in these social bees.
• Differential provisioning strategies directly influence the development of reproductive (queens) versus non-reproductive (workers) individuals.
• These findings highlight the ecological plasticity within Halictinae species in response to resource availability.