Mechanism

What is it about aphid/ant mutualism that is so beneficial? What do the Aphids provide to the ants for sustenance?

 

Role and attractiveness of aphid honeydew varies depending on sugar composition

Aphids use honeydew (a sugary substance extruded from the aphid's anus) to both feed and attract ants. Some honeydew sugars serve only as nouishment to ants, while others elicit trail laying behavior in the ants, alerting the rest of the colony to exploit the aphid resource. The feeding preferences shown by Lasius niger for honeydew sugars are: melezitose = sucrose = raffinose > glucose = fructose > maltose = trehalose = melibiose = xylose (Detrain et al). Only raffinose, sucrose and melezitose elicit trail laying behavior in L. niger. Melezitose in particular seems to be a cue indicating a long lasting resource worthy of significant time and energy investment in the form of protection. A Higher proportion of melezitose in aphid honey dew correlates to a higher intensity of ant attendance (Fischer et al).

 

Increased concentration of nonessential amino acids in aphid honeydew correlates with higher ant attendance

In addition to sugars that ants can metabolize for energy, some aphid species have higher concentrations of amino acids in their honeydew, further supplementing the diet of the ants and decreasing the time needed for foraging away from the aphids. Asparagine, glutamine,glutamic acid and serine (all nonessential amino acids) were the predominant amino acids in the honeydew of all species (of the six they observed)(Woodring et al). The highest concentrations of amino acids and sugars are found in the the ant attended species of aphids, while the lowest concentrations of of amino acids and sugars are found in the the unattended species.