Gaudy sphinx (Eumorpha labruscae)
The family Sphingidae consists of about 1400 moths known as “sphinx” or “hawk” moths. Adults generally have an elaborate stature, holding their wings slightly above their abdomen. Sometimes, their abdomen is upcurved. Sphinx moths can usually be easily coaxed onto a gentle hand Their posture is commonly alluded to the shape of a large plane. Most, if not all adults feed using a proboscis.
White-lined sphinx moth (Hyles lineata) feeding on nectar, showing the lengthy proboscis.
Their larvae are commonly known as hornworms, although they are not members of the phylum Annelida, which consists of earthworms. They are called hornworms due to their caterpillar-like shape and many of these species have hornlike appendage at the end of their body. The horn is harmless, and is present to ward off predators. The horn varies within species and instars (instars are different stages the caterpillar goes through prior to pupation), and can be granulated (rough) or smooth. The horn also can be different colors, and can sometimes help with species diagnosis. Some horns are short, and some are longer and thin. Some caterpillars have a horn which is replaced by a glassy button-like structure in later instars.
Abbott’s sphinx moth caterpillar (Sphecodina abbottii), showing the glassy button-like structure in place of a horn.
The family Sphingidae was surprisingly not named for the unique wing posture of the imaginess (an imago is full-grown insect, imagines are many full-grown insects), but for the common resting position of the larvae. The larvae frequently hold their head and first few segments up in the air, resembling the dignified pose of the Ancient Egyptian statues. Moths in the Sphingidae family have been recorded to fly 53 km/h, equivalent to about 40 mph!
Sphinx moth caterpillar (Eumorpha sp.) in the popular “sphinx” posture.
Taxonomically, sphinx moths are divided into three main subfamilies, Macroglossinae, Smerinthinae and Sphingidae. The subfamily Macroglossinae consists of smaller, yet more ornate sphinx moths. The hummingbird moths, of the genera Macroglossum and Hemaris can be found in this subfamily. Hummingbird moths sometimes have clear wings, and long proboscides for feeding on nectar. An uncommon habit of many moths, hummingbird moths are diurnal (active during the day).
African hummingbird moth (Macroglossum trochilius)
The subfamily Smerinthinae consists mostly of moths known as eyed hawkmoths. Of these eyed hawkmoths, genus Smerinthus is very widespread. These moths are called eyed sphinxes or eyed hawkmoths because they have a colorful hindwings with an eyespot. The eyespots are shown when the moth feels threatened to fool predators. Other moths in this subfamily do not have such elaborate hindwings, but the hindwings are uniquely placed so that they can be seen poking from the outside edge of the forewing.
One-eyed sphinx (Smerinthus cerisyi) displaying eyespots.
The subfamily Sphinginae consists of the larger sphinx moths, which tend to be grayish in color. However, some can be very colorful. They tend to have lines going across both forewings which form a wavy pattern. Sphinginae in the genus Agrius and Manduca have spots on either side of the abdomen which are vibrant colors.
Carolina Sphinx (Manduca sexta) showing the colorful abdominal spots.
Sphinx moths must warm their bodies by vibrating their wings in order to fly. This adaptation also enables them to survive in slightly cooler weather than other moths. Gilbert Waldbauer describes this activity in his book, The Handy Bug Answer Book. He explains that sphinx moths “warm themselves by increasing muscular activity. Although sphinx moths cannot fly unless their body temperature is between 95 degrees Fahrenheit and 100 degrees Fahrenheit, they can fly when the air temperature is as low as 50 degrees Fahrenheit. A pre-flight warm-up raises their bodies to the requisite temperature as their wing muscles generate heat by vigorously vibrating the wings. This is not unlike the shivering of the body that people experience when they are chilled.”
Modest sphinx (Pachysphinx modesta) vibrating wings to “warm up.” Don’t forget to check out the video in the spotting, too!
Sphinx moths are large-bodied insects which until recently were thought to be nearly helpless when it comes to evading bats. However, research by Akito Kawahara and Jesse Barber suggests at least three species of hawk moths use their genitals to interfere with the echolocation bats use to locate their prey. The hawkmoths emit high frequency clicks from their genitals. Tiger moths from the Erebidae subfamily of Arctiinae were previously the only moths known to emit high frequency clicks. However, tiger moths emit these clicks from structures known as tymbals in their thorax, not their genitals. This recent research is a reminder we still have much to learn about moths and their nighttime allies. Akito Kawahara best explains this: “So much work has been focused on animals that are active during the day, but there are a lot of really interesting things happening at night, and we just don’t know a lot about what is actually going on — because we can’t hear or see it… The fascinating part is that there are a lot of new discoveries to be made. It’s a totally unknown, unexplored system.”
Yam hawk moth (Theretra nessus), one of the species of moths used in the study, along with Cechenena lineosa and Theretra boisduvalii
It is amazing that scientists are still discovering more about these large and fascinating insects. Studies like those done by Akito Kawahara and Jesse Barber raise the questions, “What else is out there to discover?” and “What can I discover?”
Further reading