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Invader from the Desert

Posted 4/29/2008

I received a call on April 22 about a large caterpillar invading the northeast edge of Mesquite. The caller was concerned about possible damage to landscape plants. When I called Jeff Knight, Nevada Department of Agriculture Entomologist, to confirm what we thought the insect was, I found out that we were lucky enough to have Jeff in the southern part of the state and he was visiting Mesquite that very afternoon.

The invader is the White-lined Sphinx Moth (Hyles lineata) larvae and is very common in Nevada. The adult is also called a hummingbird moth or Hawk Moth.

The White-lined Sphinx Moths are among the largest flying insects of the deserts, with adult wingspans exceeding 5 inches and length ranging from 2 1/2 to 3 1/2 inches. These stout-bodied moths have long narrow forewings and shorter hindwings. The moth has a prominent brown head, a brown thorax with 6 white stripes and a brown abdomen with paired dark spots on each segment. The forwings are brown with a buff-colored band from base to tip and outlined veins outlined in white. The hind wings are pink, turning brown near the margins. The flight of White Lined Sphinx Moths is very quick and graceful and they can hover over flowers before zooming over to another area in a manner very similar to that of a hummingbird. Because this flight pattern requires so much energy and produces such large amounts of body heat, the White-lined Sphinx Moth usually emerges at dusk to seek out flowers whose nectar has a high amount of energy-giving sugar in the fluid. They polinate evening primroses, honeysuckle, columbine, jimson weed, clover, orchids and petunias while sucking their nectar with their long feeding tube.

Before Sphinx Moths are moths, they are a rather ugly looking caterpillar (larvae)! These larvae will burrow underground and change into moths there. The mature White-lined Sphinx Moth must then dig its way up to the surface.

The large horned larvae can be up to 3 1/2 inches long when full grown. The larvae are variable in color and color pattern, but most are black and yellow and some are green. The head, cervical shield, lateral plates on the prolegs and anal prolegs are yellow/orange flecked with white and numerous setae. The caudal horn (at the rear of the fleshy body) is also yellow/orange and prominent. When alarmed, these larvae rear up their heads in a threatening sphinx-like posture and may emit a thick, green substance from their mouths. They are very rarely pests and are often only seen when numbers get very large and sometimes large "herds" can be seen migrating across the rangeland. They are usually seen on many desert plants, especially after rains. After they consume the available plant foliage they migrate in search of other acceptable plants and are often found crawling in large numbers on the pavement of highways and are often crossing in both directions. This occurs throughout the warmer parts of Nevada.

Generally insecticides are not needed for control of White-lined Sphinx larvae because their feeding is usually confined to weeds. Keep in mind that the moth is beneficial for weed control and pollination when considering control. However, if they should attack valuable plants such as roses, small numbers can be hand picked and destroyed but if they are too numerous to control by hand, a wide range of insecticides will provide effective control. When using an insecticide make sure it is labeled for the intended use and read and follow label directions.

The University of Nevada Cooperative Extension is an outreach arm of the University that extends unbiased, research-based knowledge from the University of Nevada-and other land-grant universities-to local communities. Educational programs are developed based on local needs, often in partnership with other agencies and volunteers. For more information about the University of Nevada Cooperative Extension, please visit the website at www.unce.unr.edu or call (702) 397-2604 or 346-7215.

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