Episode 158 – Thorn Bug: Thorin Oaken-eater

“…and today we’re talking about a bug with a prickly personality. But more on that later.” 

The tropics are teaming with life. That means there’s an abundance of resources for you and your brood to enjoy. It also means that there’s plenty of competition looking to eat your food or eat you. Protecting yourself can mean developing one of several tactics. You could focus on defense, you could try to blend in, or you could try to go for both at once. The thorn bug has done just that. But with great tools, the next thing is to perfect their application in real Life, Death, and Taxonomy. 

Description of the Thorn Bug

  • These guys ain’t called thorn bugs for nothing. 
  • Start with a typical oblong cicada shape with those folded clearish wings
  • They have green heads with large, bright-red eyes and six legs coming out from underneath the body
  • Then add a giant thorn on top of its back – called the pronotal horn. From the crown of its head, the green thorn sticks up and curves slightly backward with a sharp reddish tip before cresting back down to the end of the abdomen
  • It goes without saying that the goal is to look as much like a thorn as possible. This deters predators (mainly birds) not only because they have sharp bodies but also because birds generally don’t want their toes poked

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words measure up into ldtaxonomy at gmail dot com. We don’t have a Measure Up intro this week, which means we get to hear from an animal and Carlos has to guess what it is.

  1. Gibbon
  2. Lemur
  3. Marmot
  4. Baboon


  • 10 millimetres (0.39 in)
  • How many thorn bugs go into the length of the average thorn from a honey locust tree?
  • Hint: The tree is a deciduous tree that’s native to North America, especially states around the Mississippi River. 
  • 10 thorn bugs. Thorns can be 3–10 cm (1.2–3.9 in) long.

Egg Cluster Size

  • 100
  • How many thorn bug egg clusters go into the largest group of passenger pigeons ever recorded?
  • Hint: Passenger pigeons are a now extinct species of American pigeons, that were once so numerous in American skies that a flock could take hours to pass overhead. In 1866, a gathering was recorded as being a mile wide and 300 miles long. Hunting, deforestation, and other variables are said to have driven the bird to extinction.
  • 35 million clusters. The flock was estimated to be 3.5 billion members strong. 

Fast Facts about the Thorn Bug

  • Range: Lives on trees in the tropical and subtropical zones of southern North America and northern South America. If the temperature ever drops below 0, up to 90% of the population could die off.
  • Diet: they exclusively eat the sap inside the plants they hang out on

Major Fact: Nymph Defense System

The thorn bug is an attentive mom and, unlike some other bugs, watches over her brood in the nymph stage. Mothers will find an ideal host plant to lay her eggs in. She does this by carving out a groove in the stem of the plant and depositing eggs inside it. 

Moms may even sit on eggs like a chicken, in order to protect them from would-be predators. When eggs hatch, mothers will continue to protect the clutch of nymphs until they’re big enough to strike out on their own. 

Every time a predator approaches, it’s a gamble. Should the mother maintain the illusion that she is just a thorn, or should she attack and ward off the potential danger. The gamble is fairly high. If the mother breaks the illusion and fails to fight off the predator, the clutch survival rate drops from 53% to 27%.

In order to maximize intel about the potential threat, the nymphs will help by scanning the area. When they perceive a threat, they send out a chemical signal to the mother. But mom won’t attack unless all the nymphs send out a chemical report in unison. When one nymph sends out a signal, the next either immediately responds by lighting the beacons of Gondor or not. The brood essentially decides whether or not the mother should be deployed, based on the potential danger of the threat.

Once the mother is dispatched and returns without being dispatched from this mortal coil, she decides when the threat is over and calms the brood. 

If she goes the way of Bambi’s mother, the brood may be adopted by a nearby thorn bug mom. Though, combining clutches lowers the survival rate.

Large clutches can drain resources quickly. So much so as to stunt the growth of an entire tree or kill it outright. For that reason, very successful moms may produce many small thorn bugs. Small females may still have the chops to reproduce successfully like their mother before them. But small males struggle to compete for mates and food. This has led to a disparity in the ratio between the sexes with more females than male thorn bugs. 

Ending: So stick to your branch, keep an eye out for danger, and honor the chemically-induced vibration signals from your brood mother like the thorn bug here in LDT