Cicada Killer - Sphecius speciosus


Over a long period of time, organisms, including the cicada killer wasp (Sphecius speciosus), have managed to better adapt to their environment.  When looking at a common ancestor of the cicada killer, as well as other similar, extant organisms within the order Hymenoptera, one difference in regards to form and function may be made apparent.  Where as the previously mentioned organisms have a set of setae on the back of their hind legs in order to brush off dirt particles, the cicada killer (Sphecius speciosus) has what are called, “spurs,” at the same exact position (Coelho and Holliday, 2008).  These spurs are not used, however, to remove soil from the body, rather they are used as a tool for excavating nests (Coelho et al., 2008).

As referred to in the section, Habitat, cicada killers use their mouth to dislodge soil when creating a nest.  Additionally, in order to shovel out excess soil, the cicada killer backs out of the forming nest, pushing away mounds of debris with their hind legs.  Is it a coincidence that Specious speciosus are one of the few organisms to possess these spurs given their distinguished digging technique?  The answer is no.  Cicada killers have adopted this beneficial trait as a result of Natural Selection (Coelho and Holliday, 2008).  With these larger spurs, cicada killers are able to dig much more efficiently than if they possessed ancestral setae.

One aspect that comes into discussion, though, regarding spurs is the idea of sexual dimorphism.  Since males do not dig the nests, they have much less of a need for the spurs, themselves.  As a result, the females have much larger spurs than do the males.  Additionally, females are also larger in overall size than males.  There is support for the hypothesis that due to their demand for both hunting and transporting cicadas back to the nest, females have increased in size over time (Coelho et al., 2008).  Together, these two examples of sexual dimorphism present biologists and others with observable adaptations that can be easily understood.

Likewise, another observable adaptation of the cicada killer surrounds its very name.  To explain, cicada killers have positioned the timing of their life cycle to coincide with that of their prey’s (Lafayette College, 2012).  As a result, this simple adaptation increases the survival rate of cicada killers due to the available amount of food.

Sphecius speciosus have also been able to decrease their energy exertion by conveniently adapting an alternative food source.  In order to provide food for their young, cicada killers search for their prey, cicadas, that primarily reside in trees.  Once the cicadas are found and brought back to the nest, the predatory cicada killer will return to the same tree in which their prey was found in order to feed on its food source: sap.  Cicadas bore holes in trees to contract the sap within.  Thus, when killed, cicada killers utilize these holes as a valuable source of food.  Ultimately, without the assistance from cicadas, the sap would not be available (Australian Museum, 2009).

Finally, cicada killers have adapted the ability to alter their body temperature.  It has been discovered that in order to increase body temperature, cicada killers physically vibrate their wings.  This method heats up the muscles of cicada killers so that they can be agile in flight.  Additionally,
Sphecius speciosus manage their body temperature using the energy from the sun.  When trying to increase their temperature, the wasps will face perpendicular to that of the sun; likewise, when trying to decrease their temperature, the wasps will face parallel to that of the sun (Coelho, 2001).

As with any other organism, cicada killers have many more adaptations that they exhibit.  However, the ones mentioned above are either those that are specific or critical to the survival of the organism at hand.