JULY
1998

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

7-23-98

Singing and Stinging Insects Can't Hide Their Sex

The general rule in the animal world is that females and males of the same species look different. Sometimes the difference is in size or color. Birds are often examples of color differences between sexes. Differences also might include the presence or absence of horns. This is the case in some deer and sheep.

Scientifically, a different look between males and females of the same species is known as sexual dimorphism. And the differences are-you guessed it-related to reproduction.

To the untrained observer, male and female insects look the same. In some instances, even experts on insects can't tell bug girls from bug boys. Such a determination would involve dissection of the insect to look at the internal workings.

There are obvious differences between the sexes in some insects. Sometimes the difference is most noticeable in behavior. For instance, any adult insect that stings is a female. That's because the stinger is the insect egg-laying device known as an ovipositor.

Bees and wasps are well-known insects with stingers. However, the females don't fly around with their stingers out in the open. So, for most people, getting stung by a bee or wasp is the only sure way to know that the insect is a female. To make matters worse, some male wasps, like the cicada killers, actually act like they are trying to sting. This female impostor actually goes so far as poking you with the end of his abdomen!

The ovipositors of female grasshoppers, katydids and crickets are obvious extensions of the abdomen. These ovipositors resemble curved knives, which is how they function, since they are used to cut plant tissue or soil to deposit eggs.

In some insects, males and females look entirely different. One of the most obvious differences has to do with wings. Males have wings and females do not. This is true of some fireflies. There are also some moths where the male is the only sex with wings. It is true of that pest of evergreen trees and shrubs, the bagworm, where the female stays in the bag. The infamous gypsy moth female is also wingless.

In some of the large walking sticks that thrive in tropical regions, the males are winged while the females are wingless. In these insects, the females are also much larger, making the males the "Jack Sprats” of the insect world.

Size-wise, preying mantid males are also lightweights when compared to their females. So when a preying mantid female decides to devour her mate, the poor male is fighting up a weight class or two.

Many male moths have fuzzy antennae compared to females of the same species. That difference is related to detecting the chemical mating perfumes released by the female. The chemicals are trapped in the fuzzy antennae of the male and tell him somewhere up wind is a female looking for a mate.

Male mosquitoes also have fuzzy antennae. In this case, the antennae allow them to pick up the sounds of the wing beat made by female mosquitoes. That is the same sound that we hate to hear in our ears. To the male mosquito, it is music to his antennae.

Some of the most obvious sexual differences in the insect world are associated with stag beetles. The males of these beetles have large horn-like projections that are used in battles between the males. Like their mammal namesakes, the males butt and push each other in contests for territory and females.

The male monarch butterfly has a black spot on each hind wing, something that the female lacks. The black spot is a scent gland that produces a chemical attractive to the female of the species.

Male insects are the songsters of the insect world. Sounds of katydids, crickets, grasshoppers and cicadas are produced by the male to attract their females.

It is not always easy to tell a female insect from a male. But of this we can be sure: if it stings, it is female; if it sings, it is male!

 

Writer: Tom Turpin
Editor: Olivia Maddox