How do tiny bugs feed through thick barriers? 

For my dissertation research, I am studying mouthpart development and feeding behavior in juvenile leaf-footed bugs. These juvenile bugs, called 'nymphs', are essentially tiny versions of adults, which means that they have much smaller mouthparts than adults, but somehow still manage to feed on the same fruits and seeds. In the case of western leaf-footed bugs (Leptoglossus zonatus), both nymphs and adults can feed through the thick rinds of citrus fruits and the hard shells of pecans, among other tricky food sources. The mouthparts of these bugs are long thin tubes that must pierce through these barriers and reach all the way to the food inside it. So when the bugs eat food with thick barriers, mouthpart length really makes all the difference.

Photo by Tessa Ricker

I wanted to test whether nymphs might actually grow longer mouthparts when raised on food with thicker barriers, thus enabling them to optimize their mouthparts to the food they have available. To do this, I created agar gels (similar to gelatin) with sunflower seeds embedded either just below the surface, creating a thin barrier to feeding, or deep within the gel, creating a thick barrier. The photo to the left shows a nymph on one of the 'thick barrier' gels, which requires sticking its mouthparts all the way through the gel to reach the sunflower seeds underneath.

​As expected, the bugs raised with thick barriers on their food had longer mouthparts at adulthood than those with only thin feeding barriers. However, the bugs that had to feed through the thicker barriers also died in higher numbers. Overall, it seems likely that these bugs can flexibly adjust their mouthpart development to fit their environment, an ability called developmental plasticity. However, even with this plasticity, survival is still strongly limited by extreme feeding barriers.