Using Beneficial Insects by Rhonda Massingham Hart

Author:Rhonda Massingham Hart
Language: eng
Format: epub
Publisher: Storey Publishing, LLC
Published: 1991-03-25T16:00:00+00:00

The Predators

Ladybugs/Ladybird Beetles (Hippotamia convergens)

“Ladybug, ladybug, fly away home . . .” If it’s your home she’s flying to then you’re in luck! These cute little spotted beetles are voracious predators of aphids, mealybugs, scale, spider mites, insect eggs, and corn earworms.

Most of us recognize the adult form of this gardeners’ darling, but true to insect form, the other stages of development bear no resemblance to the familiar adults. Adult ladybugs may well have inspired the endearment “cute as a bug.” Bright orange-red, rounded little beetles, they average about ⅜ inch long and are nearly as wide. Like all insects, they gad about on six legs, theirs being short, black, and spindly. Their red wing covers are decorated with a sprinkling of black spots, the number, size, and placement of which vary with the species. White markings embellish the shiny black thorax, or center segment. Their heads are also shiny black.

But don’t dare to compare the youngest maidens with the adults. Eggs laid on plants pestered by aphids or other ladybug prey may be mistaken for those of some despicable pest. Learn to spot the clusters of small, oval, bright yellow eggs.

Tiny, yellow, and black, multisegmented larvae hatch from these eggs and go through several stages, or instars, the last being the largest and the hungriest. Each larva may devour several hundred aphids, earning them the nickname “aphid wolf.” Within about twenty days from hatching, these plump, feasting larvae undergo a brief metamorphosis, from which a tender, pale adult beetle emerges. The bright color and markings develop quickly.

Adult egg-laying beetles can put away two hundred aphids per day. Their life expectancy is only a few weeks, but these mature insects produce several generations per season, ensuring a constant supply of hungry ladybugs.

Both larvae and adults are active daylight hunters. They will prowl the garden, especially plants targeted by soft-bodied pests; the adults will even take wing in their search for food. All this activity is one of the prime reasons that ladybugs have such high nutritional demands. Upon spotting their prey, the ladybugs grasp it with powerful jaws and consume it live. The habits of such prey as aphids, scale, etc., are such that large, nearly immobile groups are often found together. The ladybugs will stay in one place, gorging on their fill of pests, continuing on their endless search only after cleaning up the immediate infestation.

In the western United States, ladybugs migrate in the fall to mass hibernating sites high in the mountains. Eastern varieties may congregate under garden litter for the winter. Warming spring temperatures trigger the beetles to migrate and disperse. During most of the year, nearly every North American habitat can claim some native species of ladybug.

Invite the neighborhood ladies to make themselves at home in your garden by incorporating their favorite flowering plants into your landscape. Angelica, buckthorn, euonymus, and yarrow will entice them. Special favorites include marigolds (especially the dainty, single-flowered Lemon Gem variety), butterfly weed, and tansy. By tucking some of these in

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