What are the two functions of the bacterial secretion produced by the female beewolf (Philanthus triangulum)?

• A. It accelerates pupation and enhances flight.
• B. It marks the nest and helps in navigation.
• C. It provides a cue for larval cocoon orientation and inhibits microbial infection during overwintering.
• D. It acts as a nutrient source for larvae and repels parasitoids.

Answer: (C)

Beewolf females rely on a symbiotic bacteria that they carry and deposit in the brood cell walls. The main idea being tested is that this bacterial secretion serves a dual role in protecting developing offspring and guiding cocoon formation.

First, the bacteria produce antimicrobial compounds that inhibit microbial and fungal infections during the pupal stage, especially during overwintering when the larva is enclosed in a cocoon and vulnerable to pathogens. This protective effect helps ensure the pupa can complete development without being spoiled by fungi.

Second, the secretion leaves a chemical cue that the larva uses to orient its cocoon properly within the cell. This orientation cue helps the cocoon develop and position correctly for metamorphosis, which can be important for successful emergence and access to resources later on.

So, the two functions are antimicrobial protection during overwintering and a cue that guides cocoon orientation. Other proposed roles, like accelerating pupation or marking the nest for navigation or providing nutrients, aren’t supported by the same combination of observed effects and the biology of this symbiosis.