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Ladybug talk, Long-life link

Q: How do ladybugs communicate? (Yves, Laval, Canada)

A: Some insects use sound to communicate. Grasshoppers talk to each other by rubbing body parts like a fiddle bow against strings. Cicadas pop sound boxes on their abdomen and make a noise as loud as a jet engine. A few insects, such as lightning bugs and fireflies, flash light to pass messages.

Asian ladybug dining on an aphid. [Courtesy of Scott Camazine ©, used with permission.]

But most insects use odor and the ladybug is one of this big bunch. Since the 1870s, when we first observed this phenomenon, we have identified hundreds of insects that produce chemicals to attract the opposite sex.

The ladybug uses those chemicals called pheromones to attract, repel, and hunt.

Asian lady beetles like to find a warm home and huddle together hibernating in a great swarm during the winter months. They may use visual cues (for example, a sunlit wall) or chemical cues or both to locate a good spot. Perhaps, when one ladybug finds a good place, she emits a pheromone to let others know. More may detect the odor, follow it to the spot, and pile on the growing heap of a hundred or more.

The colorful little beetles protect themselves from harm with a different pheromone. Try picking up a ladybug. He’ll think "threat" and squirt a yellow foul-smelling-and-tasting chemical through his leg sockets. The message to hungry birds and their ilk: "Eat me and die!"

Yet another pheromone — not of the ladybug’s making — signals food. Aphids emit a pheromone to other aphids that (unfortunately for them) ladybugs can smell. It’s like a big sign flashing: "ladybug diner — open for business."

Further Reading:

WonderQuest:  Where do ladybugs live?

Ohio State University: Multicolored Asian Lady Beetle by Susan C. Jones and Joe Boggs

North Carolina State University: Insect senses by John R. Meyer

Purdue University: Insect odors worth a thousand words by Tom Turpin

Q: I read with interest your response as to why larger animals live longer than small animals (slower metabolism and having a limited number of breaths and heartbeats). But we are all encouraged to exercise in order to live longer. Exercise uses up the breaths and heartbeats faster than someone at rest. So, any idea at which point they cancel each other out? (Carolyn, Charlotte, North Carolina)

A: A high rate of metabolism is the key to the answer. Remember, the striking outcome of John Speakman’s  study was on the tissue level. Tissue in small animals, who have high metabolic rates, lives longer than tissue in larger animals. Thus, mice and other small animals live longer lives in terms of heartbeats than larger animals.

Dallas Cowboys Joey Galloway’s metabolism is racing as he catches a 26-yard pass. [Jessica Leigh/AP]

"So, exercise not only increases our numbers of heartbeats, it also increases our metabolic rate," Speakman emails, "and there is good evidence that it [exercise] is linked to decreases in all causes of mortality."

It appears that linking life span with a fixed number of heartbeats is "too simplistic." More important is a high metabolic rate.

Further Reading:

WonderQuest: Life spans about a billion heartbeats

Journal of Experimental Biology: 2005 May; 208(Pt 9):1717-30. Body size, energy metabolism, and lifespan by John Speakman

(Answered Nov. 1, 2005)