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Plant Industry - Plant Protection Section

Gypsy Moth

Introduction and Life Cycle

Gypsy moth (Lymantria dispar) is a European forest pest that feeds on the leaves of over 300 different species of trees in North America.  The damaging stage is the larval or caterpillar stage.  Larvae have been known to consume up to one square foot of leaves each by the time they reach maturity.

The gypsy moth life cycle starts when the larvae hatch in the spring.  Hatch usually occurs shortly after oak foliage begins to expand.  Larvae often remain on the spent egg masses until a warm day arrives, at which time they journey to the foliage and begin eating. 


photo courtesy of: USDA Forest Service Region 8 Archive
www.forestryimages.org


Gypsy Moth instar stage - click image to enlarge
photo courtesy of: USDA Forest Service Rocky Mountain Region Archive
www.forestryimages.org


Larval growth is categorized by instar, of which there are five or six.  Molting, the process where the caterpillar sheds its exoskeleton so it can grow larger, defines the transition between each instar.  Male gypsy moth caterpillars go through five instars, while females go through six.  Each instar lasts roughly two weeks, depending on weather.
Gypsy moths then move into pupation by transforming into a cocoon and spinning a thin web of silk around themselves.  Male and female pupae differ in size and coloration.  This phase lasts roughly three weeks. Pupation state of gypsy moth
photo courtesy of: Pennsylvania Department of Conservation and Natural Resources, Forestry Archive www.forestryimages.org  

Male Gypsy Moth
photo courtesy of: Male gypsy moth, Thérèse Arcand, Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre

Upon completion of pupation, the gypsy moth splits the cocoon to emerge.  The male emerges first, several days prior to emergence of the female. 
The female of the European gypsy moth is flightless (the female of the Asian gypsy moth, Lymantria dispar dispar is able to fly; NC had a serious infestation that was eradicated in 1994).  Adult gypsy moths do not feed; their sole function is to reproduce.  Once the female emerges, she is sexually mature, and almost immediately begins releasing sex pheromone to attract male moths.  
 

Male moths use this pheromone to locate the female moth.  After mating, the female lays an egg mass, usually composed of between 300 and 1000 viable eggs.  Both the female and male moths die shortly after mating.

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NCDA&CS Plant Industry Division - Plant Protection Section
Plant Pest Administrator - Phillip L. Wilson
Mailing Address: 1060 Mail Service Center, Raleigh NC 27699-1060
Physical Address: 216 West Jones Street, Raleigh NC 27603
Phone: 919) 707-3753 | FAX: (919) 733-1041