The hungry fly: Hydrodynamics of feeding in the common house fly

Authors: Manu Prakash, Miles Steele

Link: https://aip.scitation.org/doi/10.1063/1.3640023?cookieSet=1

DOI: https://doi.org/10.1063/1.3640023

Abstract: Many common insects including mosquitoes and flies primarily live on a liquid diet. Being small in size, pumping fluids poses a unique challenge insects need to solve. As the size of the creatures scales down to microscopic regimes, viscous forces dominate and it requires significant energy to pump fluids. For a given liquid diet such as nectar, viscosity of the fluid increases exponentially to the sugar concentration while the energy extracted from the solution only increases linearly with the amount of sugar present, presenting a severe constraint for pumping mechanism for insect feeding.1

Here, we directly visualize feeding in the common house fly, Musca domestica (Fig. 1(a)) via absorption X-ray microscopy. A starved fly is fed sugar solution of a known viscosity and sugar concentration, while fluid flow through the pump is observed in real time. A small amount of contrast agent is added to the feeding solution to provide a clear trace of fluid transport during a pumping cycle (Fig. 1(a) inset). Various X-ray imaging protocols were developed to allow for high resolution imaging using a simple table-top X-ray source. The pulsatile nature of the cibarial pump (Fig. 1(b)) in flies is depicted in Fig. 1(c). Via direct visualization of fluid flow during a single feeding stroke in flies, fluid-structure coupling of the pump geometry is revealed.

Additional Information:

The poem by William Oldys perfectly sums up this work which started as a curious inquiry into the nature of pumps in insects. Entomologists have long described the physical layout of mechnical machines we call insects, but the dynamics of how these machines work has never been seen before. Miles and I rigged up Xray microscopy setups to image insects in all the glory (in-vivo). From what we can tell, these are some really efficient pumps.

On a Fly Drinking Out of His Cup
Busy, curious, thirsty fly!
Drink with me and drink as I:
Freely welcome to my cup,
Couldst thou sip and sip it up:
Make the most of life you may,
Life is short and wears away...

By William Oldys (1696-1761)