Egg Chill Requirements

Research Issue

Diapause of the mature embryonic larva within the egg is a lengthy (8-9 mo/yr) and a critical portion of the life cycle of the nun moth.  Diapause enhances survival during the winter and synchronizes hatch with bud burst of preferred host plants in the spring.  The chill requirements for diapause completion and hatch of nun moths have not been investigated.  This information is required to parameterize predictive models and would be important for determining if eggs are laid on vessels or cargo would hatch in transit.  

Our Research

The hatch of eggs held for 0, 30, 60, 90, 120, 150, 180, and 210 days at 5 °C then incubated at 25 °C was evaluated.

Expected Outcomes

Knowledge of nun moth egg chill requirements required to make predictions of when eggs will hatch.

Research Results

Nun moth eggs have lower chill requirements for hatch than gypsy moths from the United States but require more chill than gypsy moth eggs from far east Russia to hatch.  Thus they could establish and may be able to adapt to a wide range of climates within the United States.

Research Participants

Principal Investigator

• Melody Keena, USDA Forest Service- Northern Research Station Research Entomologist

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/invasive_species/nun_moth/biology_ecology/egg_chill/

Developing Rearing Methods to Make Laboratory Research Possible

Research Issue

No adequate artificial diet or rearing methods existed for nun moth.  A method of rearing L. monacha on artificial diet would greatly simplify (no host foliage needed) the assessment of biological and chemical control agents, investigations of biology, behavior, and genetics, and improve reproducible results due to the standardization of the methods and diet ingredients used.  Several people have reared or have attempted to rear L. monacha on semisynthetic diets without much success.

Our Research

In this study the performance of L. monacha on several diets will be compared for two consecutive generations.  The performance parameters measured will be duration of various stages of the insect, larval survival, larval establishment, pupal weight, fecundity, mating success, sex ratio, percentage embryonation and hatch of eggs.  Various rearing techniques will also be compared.

Expected Outcomes

An artificial-diet-based rearing method will be developed for L. monacha which will allow research to continue year round, eliminate the need for host foliage, reduce resource requirements for rearing, and greatly simplify several research studies.

Research Results

The diet is agar based and contains wheat germ, vitamins, minerals, proteins, oils and other essential ingredients.  Larvae are reared initially in petri dishes then moved to paper cups (as shown in the photo) which provide a better substrate for the larger larvae (they roll around and get tangles in their own silk in plastic containers).  Smashed single-sided corrugated cardboard is provided to the females for an oviposition substrate.  The lab colony is now in its 22nd generation of continuous rearing.  

Research Participants

Principal Investigators

• Melody Keena, US Forest Service- Northern Research Station Research Entomologist
• Milan Svestka, Forestry and Game Management Research Institute, Ministry of Agriculture, Branch of Forestry, Czech Republic

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/invasive_species/nun_moth/biology_ecology/rearing_methods/

Biology and Ecology

Lymantria monacha is a typical transpaleartic species with a wide distribution from Japan, Korea, China, throughout Russia (southern parts of Russian Far East, Eastern and Western Siberia, Southern Urals, European part), and most European countries.  It occurs within a band between N. latitudes 43 57 including southern England, Denmark, Sweden and Finland in the North, and Spain, Portugal and Italy at elevations of 1000-2000 m in the South. The proactive research done under quarantine

Adult Lymantria monacha fly from the middle of July to the beginning of September (exact time depends on the climate of the region).  Males are nocturnally active and females release a pheromone to attract the males.  The adults are most active in the hours around midnight and the males are much more active than the females.  Although females fly, they usually sit on stems to await the male.  Once mated, the females lay from 70 to 300 eggs in clusters of approximately 40 eggs in bark crevices or under lichens on the bark.  After depositing most of her eggs, the female may fly more actively.  The L. monacha embryo completes development 2-6 weeks after the egg is laid (depending on temperature) and then enters diapause for about 10 weeks.  Hatching usually occurs in the beginning of May.  First and second instars are capable of wind dispersal over considerable distances.  Larvae have 5-7 instars and pupation takes place in July.  Males typically emerge a few days before the females.  

Our Research

• Develop Rearing Methods to Make Laboratory Research Possible 
• Egg Chill Requirements
• Phenology of Nun Moth

Last Modified: 10/21/2010

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/invasive_species/nun_moth/biology_ecology/

Potential Oviposition Substrates

Research Issue

Nun moth has the potential to be transported via commerce because eggs are laid in crevices of bark and could be laid in the cracks of vehicles or cargo such as containers, pallets, ships, etc.  Adults are readily attracted to artificial lights and have been observed on Russian ships in Far East ports.  There was no information on how readily nun moths would use plastic, metal or wood cracks for ovipositon.

Our Research 

Adult females were provided plastic, metal, wood or cardboard cracks to use for oviposition in a no choice test.  The number of eggs laid on each substrate was determined.  Further work providing choices between substrates is needed.

Expected Outcomes

Information on the substrates that female nun moths will use for oviposition to direct searches for eggs on vessels and cargo.

Research Results

When bark cracks (their usual oviposition substrate) are not available, nun moths will lay their eggs in plastic, metal or wood cracks.  This could increase the potential introduction when transportation terminals are adjacent to lights and outbreaks of nun moth.

Research Participants

Principal Investigators

• Melody Keena, USDA Forest Service- Northern Research Station Research Entomologist
• Toni Withers, New Zealand Forest Research Institute

Last Modified: 09/18/2009

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/invasive_species/nun_moth/risk_detection_spread/oviposition_substrates/

Lymantria monacha (nun moth) and L. dispar (gypsy moth) survival and development on improved Pinus radiata

Author

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• Withers, T.M.
• Keena, M.A.

Year Published

2001

Publication

New Zealand Journal of Forestry Science. 3(1): 66-77.

Abstract

The lymantriid forest defoliators, Lymantria monacha L. (nun moth) and Lymantria dispar L. (gypsy moth) are particularly severe pests in other countries in the world, but the ability of these moths to utilise and complete development on Pinus radiata D. Don had never been established. In laboratory trials, colonies of central European L. monacha and Russian far east (flight capable) L. dispar were fed on foliage from three mature P. radiata trees originating from three different advanced-selection families from New Zealand. The results showed that both moths were capable of completing their development from egg to adult on these families of P. radiata. However, P. radiata was a less suitable host for development of L. dispar than Quercus velutina Lam. (black oak), as evidenced by higher mortality and slower growth. Lymantria monacha developed faster and survived better on P. radiata than it did on mature foliage of Picea glauca (Moench) Voss. Neonate L. monacha larvae favoured male pine cones from Pinus strobus L. as a food source, but when these were absent did complete their development on P. radiata needles. There was no difference in larval development between those on the three P. radiata families tested. The study suggests anaccidental introduction of L. monacha to New Zealand, even more so than L. dispar, could have a serious impact on P. radiata plantations.

Keywords

• Lyrnantriidae
• larval feeding
• development
• survival
• fecundity
• no-choice trial
• biosecurity risk
• Lymantria monacha
• Lymantria dispar
• Pinus radiata

Citation

Withers, T.M.; Keena, M.A. 2001. Lymantria monacha (nun moth) and L. dispar (gypsy moth) survival and development on improved Pinus radiata. New Zealand Journal of Forestry Science. 3(1): 66-77.

Last updated on: April 10, 2007

For further details log on website :
https://www.nrs.fs.fed.us/pubs/8388

Survival and Development of Lymantria monacha (Lepidoptera: Lymantriidae) on North American and Introduced Eurasian Tree Species

Author

• Keena, M.A.

Year Published

2003

Publication

Journal of Economic Entomology. 96(1): 43-52.

Abstract

Lymantria monacha (L.) (Lepidoptera: Lymantriidae), the nun moth, is a Eurasian pest of conifers that has potential for accidental introduction into North America. To project the potential host range of this insect if introducedinto North America, survival and development of L. monacha on 26 North American and eight introduced Eurasian tree species were examined. Seven conifer species (Abies concolor, Picea abies, P. glauca, P. pungens, Pinus sylvestris with male cones, P. menziesii variety glauca, and Tsuga canadensis) and six broadleaf species (Betula populifolia, Malus x omestica, Prunus serotina, Quercus lobata, Q. rubra, and Q. velutina) were suitable for L. monacha survival and development. Eleven of the host species tested were rated as intermediate in suitability, four conifer species (Larix occidentalis, P. nigra, P. ponderosa, P. strobus, and Pseudotsuga menziesii variety menziesii) and six broadleaf species (Carpinus caroliniana, Carya ovata, Fagus grandifolia, Populus grandidentata, Q. alba, and Tilia cordata) and the remaining 10 species tested were rated as poor (Acer rubrum, A. platanoidies, A. saccharum, F. americana, Juniperus virginiana, Larix kaempferi, Liriodendron tulipfera, Morus alba, P. taeda, and P. deltoides). The phenological state of the trees had a major impact on establishment, survival, and development of L. monacha on many of the tree species tested. Several of the deciduous tree species that are suitable for L. monacha also are suitable for L. dispar (L.) and L. mathura Moore. Establishment of L. monacha in North America would be catastrophic because of the large number of economically important tree species on which it can survive and develop, and the ability of mated females to fly and colonize new areas.

Keywords

• Lymantria monacha
• host plant suitability
• development
• survival

Citation

Keena, M.A. 2003. Survival and Development of Lymantria monacha (Lepidoptera: Lymantriidae) on North American and Introduced Eurasian Tree Species. Journal of Economic Entomology. 96(1): 43-52.

For further details log on website :
https://www.nrs.fs.fed.us/pubs/8382

North American Host Utilization

Research Issue

Literature on the pheromones, microbial control, and general biology and biological control of the nun moth exists.  However, there is little useful information that addresses the problems that would be encountered should the nun moth be introduced into North America.  To predict the risk of successful establishment in various North American forest ecosystems and the potential damage to those systems, knowledge of the nun moth's ability to survive and develop on various North American host plants is required.  Field observations in Eurasia have shown that nun moths can feed and thrive on the foliage of many trees, both coniferous and deciduous.  Two species it prefers and most often damages in Europe are Norway spruce (Picea abies) and Scots pine (Pinus sylvestris).  Sliwa (1987) provides an extensive list of the intensity of natural feeding of nun moth larvae on trees and shrubs in Poland during the 1978-1984 outbreak.  Laboratory investigations of nun moth preferences and utilization of Eurasian host plants provide limited and contradictory information.  Most of the host plant work done on nun moths has concentrated on the relationships between bud burst on the main hosts, Norway spruce and Scots pine, and hatching of nun moth larvae.  This work has shown that host phenology is just as important as host preference in determining the survival and successful development of nun moth larvae.  For example, when larvae hatch before foliage bud burst the presence of male flowers or buds is critical to larval survival and growth.

Our Research 

The survival and development of L. monacha larvae during their first 14 d on 26 North American and eight introduced Eurasian host plants was compared. Larvae on 11 of the hosts used for the 14-d study were allowed to complete their development on those hosts.  The host plants used were from a broad range of tree genera, representing the major forest types present in North America and included many of the major species of economic importance.  Species from Eurasia provided a basis for comparison with the results of European research and provided information on exotic hosts commonly grown in urban areas of North America. 

Expected Outcomes

Provide knowledge of the nun moth's ability to survive and develop on various North American hosts (both native and introduced) that is needed to determine the risk of successful establishment in various North American forest ecosystems and the potential damage to those systems should nun moth be introduced.

Research Results

Species in the genera Betula, Quercus, Pyrus, Abies, and Picea and Pinus sylvestris (with male cones) were suitable for Lymantria monacha (L.) (nun moth) growth and development.  Species from the tree families Aceraceae, Magnoliaceae, Moraceae, Oleaceae, Salicaceae, Tiliaceae and Cupressaceae were unsuitable for nun moth survival and development.  Other species of trees tested were of marginal suitability for nun moth growth and development.  The phenological state of the trees had a major impact on establishment, survival and development of nun moth on many of the tree species tested.  Several of the deciduous tree species that are suitable for nun moth also are suitable for Lymantria dispar (L.) (gypsy moth) and Lymantria mathura Moore (pink gypsy moth).  Nun moth establishment in North America would be catastrophic because of the large number of economically important tree species it can utilize and the ability of mated females to fly and colonize new areas. 
In a separate study, nun moth were found to be capable of completing their development from egg to adult on Pinus radiata. This suggests an accidental introduction of L. monacha to New Zealand, even more so than L. dispar, could have a serious impact on P. radiataplantations. 

Keena MA. 2003. Survival and development of Lymantria monacha (Lepidoptera:Lymantriidae) on North American and introduced Eurasian tree species. J. Econ. Entomol. 96(1): 43-52. 

Withers TM; Keena MA. 2001. Lymantria monacha (nun moth) and L. dispar (gypsy moth) survival and development on improved Pinus radiata. New Zealand Journal of Forestry Science 31(1): 66-77. 

Notes on Eurasian Hosts

In coniferous trees in Eurasia, newly hatched Lymantria monacha larvae usually move to the crowns and start feeding on young soft needles.  When young soft needles are absent, they may feed on buds and male cones until leaf bud break.  Feeding on males cones in Pinus species is often a essential to larval survival since they usually hatch before leaf bud break.  When larvae feed on open male cones of pine they often cover themselves in the pollen so they appear yellow and black.  While feeding on Pinus, Abies, Picea and Larixneedles the larvae are very destructive, they first cut the upper half off then eat the remaining part.  This results in a buildup of both frass and damaged needles at the base of coniferous trees where they are feeding.  In deciduous trees they perforate the young leaves initially then later consume all leaf tissues except the non-edible veins.  Approximately 600-1,000 larvae are sufficient to completely defoliate a P. sylvestris tree and in outbreaks there may be up to 20,000 larvae per tree. 

Primary Hosts (outbreaks occur on these)
Common name	Scientific Name	Geograpic location
Japanese Fir	Abies firma	Japan, Russian Far East Sakhalin
Cajander Larch	Larix cajanderi	South Eastern Siberia
Japanese Larch	Larix leptolepis	Japan
Norway Spruce	Picea abies	Europe
Yeddo Spruce	Picea ajanensis	Russian Far East
Korean Pine	Pinus koraiensis	Russian Far East, Sakhalin
Scots Pine	Pinus sylvestris	Europe

Chinese Hosts (quality not specified)
Common name	Scientific Name
Faber’s Fir	Abies fabri
Manchurian Fir	Abies nephrolepis
Fortune’s Keteleeria	Keteleeria fortunei
Dragon Spruce	Picea asperata
Chinese White Pine	Pinus armandii
Japanese Red Pine	Pinus densiflora
Chinese Douglas Fir	Pseudotsuga sinensis
Chinese Juniper	Juniperus chinensis
Chinese Hemlock	Tsuga chinensis
Heartleaf Hornbeam	Carpinus cordata
South Chinese Beech	Fagus longipetiolata
Chinese Aspen	Populus davidiana
Pencil Willow	Salix humboldtiana
Oriental White Oak	Quercus aliena
Korean Oak	Quercus glandulifera
Korean Mountain-Ash	Sorbus alnifolia
Tuft Leaved Lime	Tilia tuan
Siberian Elm	Ulmus pumila
Large Fruited Elm	Ulmus macrocarpa
Asian Hazel	Corylus heterophylla
Paradise Apple	Malus pumila
Apricot	Prunus armeniaca

Good Hosts (used frequently)
Common name	Scientific Name
White Fir	Abies alba
European Larch	Larix decidua
Dahurian Larch	Larix gmelinii
Yezo Spruce	Picea jezoensis
Sitka Spruce	Picea sitchensis
Lodgepole Pine	Pinus contorta
Douglas Fir	Pseudotsuga menziesii
Erman’s Birch	Betula ermanii
European White Birch	Betula pendula
European Beech	Fagus sylvaticus
English Oak	Quercus robur
Sessile Oak,	Quercus sessilis
Whortleberry	Vaccinium myrtillus
Apple	Malus domestica

Occasional Hosts (used occasionally)
Common name	Scientific Name
Colorado Spruce	Picea pungens
Jack Pine	Pinus banksiana
Austrian Pine	Pinus nigra
White Pine	Pinus strobes
Common Juniper	Juniperus communis
Norway Maple	Acer platanoides
European Hornbeam	Carpinus betulus
European Ash	Fraxinus excelsior
Lombardy Poplar	Populus nigra
Northern Red Oak	Quercus rubra
European Rowan	Sorbus aucuparia
Small-leaved Linden	Tilia cordata
Large-leaved Linden	Tilia platyphyllos
European White Elm	Ulmus laevis
Hazelnut	Corylus avellana
Spindle Tree	Evonymus europeus
Glossy Buckthorn	Frangula alnus
European Raspberry	Rubus idaeus
Pear	Pyrus domestica

 

Research Participants

Principal Investigators

• Melody Keena, USDA Forest Service- Northern Research Station Research Entomologist
• Toni Withers, New Zealand Forest Research Institute

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/invasive_species/nun_moth/risk_detection_spread/host_utilization/

Scientists & Staff

Research Reviews

• Emerald Ash Borer Research: A Decade of Progress on an Expanding Pest Problem
  Summer 2013
• New Pheromone Traps Lure Asian Longhorned Beetles Out of Hiding
  Winter 2012

News Releases

Melody Keena

Research Entomologist
Ecology and Management of Invasive Species and Forest Ecosystems
51 Mill Pond Road
Hamden, Connecticut 06514
Phone: 203-230-4308

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  Highlights

Current Research

• I develop biological and ecological information and technologies to detect, monitor, contain, and eliminate newly introduced invasive insects that are threats to U.S.
• I also maintain the capability to expand research on and respond rapidly to threats posed by Asian gypsy moth (Lymantria dispar) and nun moth (Lymantria monacha), and other high priority invasive insect species.

My research time is currently divided between:

1. Completing research on the influence of Asian longhorned beetle (ALB) mating behaviors on establishment and viability of ALB populations;
2. Developing and validating a model of ALB development based on the effects of temperature on development, fecundity, and survival;
3. Doing collaborative research to develop an ALB trap and lure combination that will be effective for detecting this insect at low population levels;
4. Doing collaborative research on ALB to determine the role host moisture content (both in living and cut wood) has on its development.
5. Doing collaborative research to develop an ash free artificial diet for larvae and improve the methods for rearing emerald ash borer (EAB)(Agrilus planipennis) so that large numbers of its parasitoids can be produced for release as biological control agents.
6. Doing collaborative research on the role that EAB mating behaviors have on fecundity and fertility.
7. Developing knowledge of the biology of Scymnus camptodromus that will allow it to be reared so that the effectiveness and specificity of this hemlock woolly adelgid predator can be evaluated.
8. Doing collaborative research on the host range of Scymnus camptodromus to determine if its release would have any un wanted non-target effects.

Research Interests

Future research may include:

1. Evaluating the susceptibility of nun moth to Entomophaga maimaiga and to specific parasitoids already established in the U.S.
2. Doing new research on a newly introduced or high risk invasive forest insect.

Why This Research is Important

With the ever-increasing volume of world trade and travel, the numbers of new introductions of forest insect pests has increased over the last few years. The most effective strategy against invasive species is to prevent them from being introduced and becoming established in new ecosystems. However, there is a significant lack of information needed to identify high risk nonnative species and priority pathways of introduction. Many of the species that are introduced may never establish, but those that do may become serious invasive pests due to the absence of natural enemies and host resistance in native species that did not co-evolve with the insect. Once these new pests have established, a quick and coordinated response to new infestations can significantly reduce environmental and economic impacts. In order to deal with these potential or established invasive pests there is a critical need to develop biological and ecological information on which to base exclusion, eradication, or containment decisions.

The Asian longhorned beetle is a native insect of China and little information about this insect was available when it was first found infesting trees in New York City in 1996. Tools to effectively detect beetle populations are still needed and there continues to be a need to increase the knowledge of the life history, ecology, reproductive behavior, and seasonal phenology of the Asian longhorned beetle (ALB) to provide the biological basis for predicting potential dispersal, developmental phenology, timing of exclusion and eradication methodologies, and development of trapping methods

The emerald ash borer (EAB), Agrilus planipennis, is a non-native insect from Asia that threatens ash trees in our urban and natural forests. EAB was found in metropolitan Detroit, MI, in July 2002 and continues to spread to additional areas and states. EAB has no known effective natural enemies in North America and control options, other than tree removal, are extremely limited. If left unchecked, the pest will continue to infest and destroy native and ornamental ash trees, resulting in losses of billions of dollars to the lumber and nursery industries as well as urban communities. Without an effective and efficient laboratory rearing method for EAB, mass rearing of parasitoids in numbers needed for field-testing/release will be extremely limited.

The hemlock woolly adelgid (HWA), Adelges tsugae (Annand), is an exotic pest native to Asia and western North America. It was first discovered in eastern North America in 1951 near Richmond, VA and has since spread to 17 eastern states threatening two species of hemlock--the eastern hemlock, Tsuga canadensis (L.) Carr., and Carolina hemlock, Tsuga caroliniana Engelm. The HWA has caused extensive mortality and decline of hemlock trees in the eastern U.S. and there are no effective native natural enemies to keep this invasive pest in balance. Thus, establishment of a complex of natural enemies from the native range of HWA offers the greatest potential for providing sustainable long-term control.

The most effective strategy against invasive species is to prevent them from being introduced and becoming established in new ecosystems. But there is a significant lack of information needed to identify high risk nonnative species and priority pathways of introduction. The nun moth, Lymantria monacha, is closely related to gypsy moth and is considered to have high potential to be introduced into this country via commerce. Research and technology development on nun moth has provided information and tools for early detection and rapid response. Gypsy moths from Eurasia continue to be introduced into North America and research provides information needed to reduce the risk of introductions and eradicate detected populations before they establish.

Last updated on : 13-Jan-2017

For further details log on website :
https://www.nrs.fs.fed.us/people/mkeena

Nun Moth: Potential New Pest (Pest Alert)

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• Author 

• Keena, Melody
• Shields, Kathleen

Year Published

1998

Publication

NA-PR-95-98. Newtown Square, PA:U.S. Dept. of Agriculture, Forest Service, Northern Area State & Private Forestry

Abstract

The nun moth, Lymantria monacha (L.)(Lymantriidae), is a Eurasian pest of conifers that could be accidentally introduced into North America. Its establishment in this country would be disastrous because it feeds on a variety of vegetation and can migrate and colonize a variety of sites.

Keywords

• Insect
• gypsy moth
• defoliation
• conifers
• deciduous.

Citation

Keena, Melody; Shields, Kathleen 1998. Nun Moth: Potential New Pest (Pest Alert). NA-PR-95-98. Newtown Square, PA:U.S. Dept. of Agriculture, Forest Service, Northern Area State & Private Forestry

Last updated on: September 1, 2004

For further details log on website :
https://www.nrs.fs.fed.us/pubs/1048/

Nun Moth

Techniques to Identify Each Life Stage and Differentiate it From Gypsy Moth 

Research Issue

The risk of nun moth accidentally being introduced to North America is thought to be high.  Regulatory officials need a good guide for identifying all stages of this insect and differentiating it from gypsy moth, a closely related species.

Our Research

The literature was examined and each stage of the nun moth was photographed.  Each stage of the nun moth and gypsy moth were compared.  Diagnostic characteristics were documented.

Expected Outcomes

Guide for use in identifying nun moth and differentiating it from gypsy moth.  The pest alert is out of print but available on the web.  Port inspectors all have copies and several specimens of nun moth have been preserved and made available for reference. 

Research Results

Eggs

Eggs of  Lymantria monacha are spherical, ~ 1 mm in diameter, slightly depressed in the middle of the upper surface and often flattened on the lower surface.  The eggs are orange brown (blue green if reared on artificial diet) at first, later turning brown with an opalescent shine.  The eggs are deposited in clumps that are glued together without a covering of hair.  The female does not deposit all of her 70-300 eggs in one place and generally hides them in crevices in the bark of trees. 

Larvae 

The hairy larvae of the Lymantriidae can always be distinguished from other families by the presence of some type of dorsal eversible glands, prominently located in the middle of the 6th and 7th abdominal segments.  Larvae of Lymantria species have a full complement of low, rounded verrucae, without dense hair tufts, and usually without hair pencils.  The dorsal verrucae bear needle like setae and sometimes longer hairs.

Newly hatched larvae are ~ 4 mm long.  At first, they appear tan but within several hours they turn black.  They are very hairy and have "air hairs" which may aid in dispersal.  The "air hairs" are simple setae with a bulb-like structure in the middle that looks like a water droplet under the light microscope.  The "air hairs" are only present on the 1st instar larvae.  

The 2nd instars appear black with a few lighter spots and have two white patches that almost encircle each dorsal verrucae on the 3rd thoracic segment but do not meet along the middorsal line.  There is also a light patch which fills the middorsal space between the verrucae from the middle of the 4th to the middle of the 6th abdominal segments.  The larvae have small-paired glands on 1st 5th abdominal segments and large single orange eversible glands on 6th and 7th which are clearly visible.

From the 3rd instar on, the head of the larva is orangish brown with numerous brown and black freckles.  The middorsal stripe is a mottled brown to black.  The dorsal verrucae of the larva are all bluish.  The dorsal spot or patch patterns present in the 2nd instar persist through the later instars.  The mature larvae appear tanish, greenish or dark grayish in color with extensive brown or black mottling and are 30 to 40 mm in length.  The color of the larvae conceals them when they rest on the branch of a conifer.

Pupae 

The pupa has no cocoon, is reddish brown, and shiny with light colored (occasionally red) clumps of hairs.  It measures 18 to 25 mm in length.  The sex of the pupa can be determined by the form of the bases of the antennal pads and by the characteristics of the future sex organs located on the external ventral portion of the abdominal segments (female on 8th segment and male on 9th).

Adults  

Lymantrid adults can usually be recognized by the position of the Sc vein relative to Rs vein in the hindwing, the base of the M2 vein being much closer to M3 than to M1 in the hindwing, the absence or vestigial nature of the haustellum, the absence of ocelli, the prespiracular counter tympanal hood, and the one to three long, divergent spinules at the end of each antennal branch (Ferguson 1978).

In Lymantria species, the females have wings that are longer and narrower than those of the male.  Female bodies are stout and antennae are bipectinate with short branches approximately the thickness of the shaft, each bearing one terminal spinule.  Male antennae are bipectinate with very long branches, each bearing one long terminal spinule and sometimes a second very short one.  Sexual dimorphism in form and color is often extreme.  When at rest the outline of the female is that of an isosceles triangle while that of the male resembles an equilateral triangle.  

Sexual dimorphism in color is much reduced in Lymantria monacha.  The forewing coloration of both sexes varies from characteristic chalk white, decorated with numerous dark transverse wavy lines and patches, to almost black specimens.  The hind wings are generally gray brown with minute dark and/or light patches at their edge.  The female has a wingspan of 45 to 55 mm while the male has a wingspan of 35 to 45 mm.  Lighter colored females have abdomens with patches of pink or red and black bands, which correspond to the intersegments.  Darker colored females have abdomens that are all dark.  The darker forms are common in Europe but totally absent in Oriental populations.  The female has an extremely long ovipositor adapted for its specialized egg laying habit.  

SIMILARITIES TO OTHER SPECIES OR CONDITIONS  

Newly hatched larvae of both Lymantria monacha and Lymantria dispar are very similar.  The L. monacha 1st instar can be distinguished from the L. dispar 1st instar (10-20X) by the presence of paired black pinaculi on the dorsal surface of the body.  Each pair of pinaculi is located in front of and between the pair of dorsal verrucae on each segment.  Under a scanning electron microscope additional differences become evident.  The L. dispar larva has a single plumose seta with virtually no pinaculum located in the same position as the L. monacha "air hair" with a large pinaculum.  Keena et al. (1998) provide a complete description of how to distinguish all stages of L. monacha from L. dispar. 

Keena MA, Shields KS, Torsello M. 1998. Nun moth: potential new pest. Pest Alert NA-PR-95-98. U.S. Dep. Agric. For. Serv., Northeastern Area, State and Private Forestry. 2 p.

Research Participants

Principal Investigators

• Melody Keena, USDA Forest Service- Northern Research Station Research Entomologist
• Kathleen Shields, USDA Forest Service- Northern Research Station Research Entomologist (Retired)
• Mary Torsello, USDA Forest Service- Northeastern Area State and Private Forestry

For further details log on website :
https://www.nrs.fs.fed.us/disturbance/invasive_species/nun_moth/risk_detection_spread/identify_life_stage/