Lady Bugs

BIO-1100 Principles of Biology

Ladybugs

By Jozef Vandenmooter

Introduction

Ladybug is the name commonly used to describe the Coccinellidae (which means clothed in scarlet), members of the Coleoptera, or beetle family. They are also known as Lady beetles, Ladybirds, Ladybird Beetles or Ladybird Bugs. The 'lady' referred to is the Virgin Mary. In German they are called Marienkafer, or Mary beetles. In Dutch we call them LieveHeersbeestjes, or Dear Lord Bugs.

The reason they are given these names in folklore is that they are considered harbingers of good luck. Indeed, many species of ladybugs feed on pests, and have therefore been introduced in the environment deliberately on many occasions.

Description

Depending on the species, ladybugs measure anywhere from .3 to 10mm in length. They have oval shaped bodies and are usually an orange to red color with black spots.

The heads and legs are retractable. Ladybugs have six legs, three on each side. They have segmented antennae and they all have functional wings.

There are about 400 different ladybug species in North America, and over 5,000 worldwide. Some of the most common ladybug varieties include the Two Spotted Ladybug, the Seven Spotted Ladybug, and the Thirteen Spotted Ladybug. In this mini-paper we will concentrate on the Coccinella septempunctata, or Sevenspotted Ladybug.

Habitat

Ladybugs are found in a wide range of habitats and are common across the globe. They can be found in gardens, forests, fields, grasslands, and occasionally inside the house! In 1999 NASA even sent four ladybugs into space! Researchers wanted to know if aphids could escape from them in zero gravity. However, the ladybug was triumphant and it survived its perilous journey into space!

The Sevenspotted Ladybug or Coccinella septempunctata, is from European origin. It first appeared in the U.S. in New Jersey, in the early 1970s, probably from an accidental introduction. Since then it was repeatedly introduced to North America from Europe for the biological control of aphids (plant lice) in wheat fields and even personal gardens, and has spread to many northeastern and north central states. Other examples where C. septempunctata have been introduced for pest control include brassica crops in Pakistan, cotton fields in China and apple orchards in Hungary, Poland, Belgium and Canada.

C. septempunctata can be so successful that native ladybug species suffer. An example of this is Maryland, where C. septempunctata displaced native C. novemnotata from nurseries.

Ladybug feeding on aphids

Both adults and larvae live on plants frequented by aphids. They have a ferocious appetite, and can consume up to 100 aphids per day. Some larvae have been clocked at eating 44 aphids in 85 minutes!

Life Cycle

Depending on temperature, humidity and food supply, the length of the life cycle is about three to six weeks.

When mating, the male fixes himself on top of the female and internally fertilizes her using his aedeagus (the insect equivalent of a penis). Female ladybugs tend to mate with many males, although this is not necessary for fertilization of the eggs. If there are abundant aphids, she can begin laying fertile eggs 5 - 10 days after fertilization. Each female can lay from fifty to three hundred eggs (tiny, light-yellow eggs are deposited in clusters of 10 to 50 each) in her lifetime, in places where she knows aphids are present.

Eggs hatch in three to five days, and larvae feed on aphids or other insects for two to three weeks. Once they begin feeding, they grow quickly. They go through 4 larval instars (shed exoskeletons) and then pupate. Adults emerge in seven to ten days. There may be five to six generations per year. In the autumn, adults hibernate, sometimes in large numbers, in plant refuse and crevices.

Ladybugs mating

Eggs are deposited underneath a leaf

After 5 to 8 days, the larvae emerge

After 3 weeks, the larvae enter