''Neodiprion abietis'', commonly known as the balsam fir sawfly, is a species of insect in the family

Diprionidae The Diprionidae are a small family of conifer-feeding sawflies (thus the common name conifer sawflies, though other Symphyta Sawflies are wasp-like insects that are in the suborder Symphyta within the order Hymenoptera, alongside ants, bee ...

. It is found in North America from Canada to northern Mexico and is

phytophagous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet (nutrition), diet. These more broadly also encompass an ...

, feeding on the needles of coniferous trees.G. Knerer, C.E. Atwood (1973). Diprionid sawflies: polymorphism and speciation. Changes in diapause and choice of food plants led to new evolutionary units. Science, USA, 179(4078), 1090-1099.

Evolutionary relationship

''N. abietis'' is considered to arise from a monophyletic group.C.R. Linnen and B.D. Farrell (2008). Phylogenetic Analysis of Nuclear and Mitochondrial Genes Reveals Evolutionary Relationships and Mitochondrial Introgression in the Sertifer Species Group of the Genus Neodiprion (Hymenoptera: Diprionidae) Molecular Phylogenetics and Evolution. 48(1): 240-257.

Internal anatomy

The larva of ''N. abietis'' have salivary glands with a lumen that is lined by

microvilli Microvilli (: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellula ...

and it also has a single layer of

epithelial cells Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

present. Moreover, they have fat body cells against the anterior duct of the lumen. Balsam fir sawfly have a pair of diverticular pouches which are used to store

terpenoids The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes" ...

which they regurgitate as a form of defense. These pouches are lined with a layer of an impermeable cuticle. The amount of liquid regurgitated is a reflection of the food that they ingest. The rectum of the ''Neodiprion abietis'' larva has a rectum similar to other

. The rectum consists of a thin cuticle, a single layer of epithelial cells, and contains muscles.C.J. Lucarotti, H.W.W. Beatrixe, and D.B. Levin (2011). Histology of the Larval ''Neodiprion abieti''s (Hymenoptera: Diprionidae) Digestive Tract. Journal of Entomology. 2012: 1-10.

Physical characteristics

The heads of instars differ in color, newly hatched first

instars An instar (, from the Latin ''wikt:instar#Latin, īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each ecdysis, moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the ...

have a light brown head and prior to molting into second instars, their heads change to a dark brown color. Their heads then turn black in color during the second to fifth instars. A range of 0.48 mm to 0.60 mm is seen with the size of head capsules. The stripes on their body also differ in larval instars. The first and second instar lack longitudinal stripes. The third, fourth, and fifth instar has three pairs of longitudinal dark stripes. The stripes on the third instar are considerably shorter than the fourth and fifth instar, while the stripes of the fourth and fifth instar are very similar causing difficulty for differentiating. The body color and length also varies between instars. Initially, a translucent body is seen, then becomes light green during the first instars. The body length rages anywhere from 2.43 mm to 3.15 mm. The antennas, more specifically their segments, differ between male and female. Male antennas consist of 21-23 segments while female antennas consist of 18-20 segments.S. Li (2003). Notes on larval instars and adult antennae of ''Neodiprion abietis'' (Hymenoptera : Diprionidae). Canadian Entomologist. 135(5): 745-748.

Life cycle

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

, Canada, female sawflies lay their eggs in late September or early October using their saw-like ovipositor into

foliage A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, f ...

of the current year or foliage of the previous year. The different strains of ''N. abietis'' are known to differ in host plant oviposition preference.R.C. Johns, J. Fidgen, and D.P. Ostaff (2013). Host–tree oviposition preference of balsam fir sawfly, ''Neodiprion abietis'' (Hymenoptera: Diprionidae), in New Brunswick, Canada. Canadian Entomologist. 145(4): 430-434. Months later, around June or mid-July, the eggs hatch and the larvae feed immediately on needles of the balsam fir. The larvae prefer to eat 2 or 3-year-old balsam fir foliage and will rarely feed on foliage of the current year.G. Moreau, D.T. Quiring, E.S. Eveleigh, E. Bauce (2003). Advantages of a Mixed Diet: Feeding on Several Foliar Age Classes Increases the Performance of a Specialist Insect Herbivore. Oecologia. 135: 391–399. The development of male and female sawfly vary slightly. Females can have five or six instars whereas males only have five instars. Secondly, females take slightly longer than males to complete their development. A female's developmental period lasts 35 days whereas males complete their development within 30 days. Male and female sawflies spin a cocoon during their last-instar larva, they pupate inside, and adults emerge from the cocoon within 2–3 weeks. Account differs concerning whether ''N. abietis'' will spin its cocoon on the foliage or in the ground.W. J. Carroll (1962). Some aspects of the Neodiprion abietis (Harr.) complex in Newfoundland. PhD dissertation, Syracuse University, Syracuse, New York, USA.D.R. Wallace and C.R. Sullivan (1973). Photoperiodism in the Early Balsam Strain of the Neodiprion abietis Complex (Hymenoptera: Diprionidae). Canadian Journal of Zoology. 52: 507-513.

Reproduction

Mated females can produce male and female offspring while unmated females can only produce male offspring, a form of

parthenogenesis Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

known as

arrhenotoky Arrhenotoky (from Greek ἄρρην ''árrhēn'' "male" and τόκος ''tókos'' "birth"), also known as arrhenotokous parthenogenesis, is a form of parthenogenesis in which unfertilized eggs develop into males. In most cases, parthenogenesis pro ...

Feeding

The balsam fir sawfly feeds on ''Abies balsamea'', a type of

fir Firs are evergreen coniferous trees belonging to the genus ''Abies'' () in the family Pinaceae. There are approximately 48–65 extant species, found on mountains throughout much of North and Central America, Eurasia, and North Africa. The genu ...

, ''Picea glauca'', ''Picea mariana'' types of

spruce A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ecosystem, boreal (taiga) regions of the Northern hemisphere. ''Picea'' ...

, and ''Larix laricina'', a

larch Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to the cooler regions of the northern hemisphere, where they are found in lowland forests in the high la ...

.P.D. Simon, M.Y Aaron, B. Morin, C.J. Lucarotti, B.F. Koop, and D.B. Levin (2006). Sequence Analysis and Organization of the Neodiprion abietis Nucleopolyphedrovirus Genome. Journal of Virology. 80(14): 6952-6960. The first instar feeds on the whole crown of one-year-old foliage following egg hatch and the larvae in a group feed together by moving from one shoot to another.L.J. Anstey, D.T. Quiring, D.P. Ostaff (2002). Seasonal Changes in Intra-tree Distribution of Immature Balsam Fir Sawfly (Hymenoptera: Diprionidae). Canadian Entomologist. 134: 529-538. Females, however, have a greater sensitivity to foliage than males and it’s suspected that it is due to their longer developmental time. ''N. abietis'' larvae have optimal development when they are able to feed on different-aged foliage thus allowing for maximization of their resources.G. Rogers, D.T. Quiring, and C.J. Lucarotti (2012). Transmission of a Gammabaculovirus within Cohorts of Balsam Fir Sawfly (''Neodiprion abietis'') Larvae. Journal of Insects. 3(4): 989-1000. Moreover, the balsam fir sawfly are considered to be wasteful feeders because only the outer portions of needles are consumed during the early-instar larvae. Late instars, however, consume more needle tissue type but it never consumes the needle in its entirety.

Ecological importance

In eastern Canada, local outbreaks of ''N. abietis'' can last anywhere from 3 years to 5 years and have been shown to have a periodicity of about 10 years.G. Moreau (2006). Past and present outbreaks of the balsam fir sawfly in western Newfoundland: An analytical review. Forest Ecology and Management 221: 215-219. Ecological factors involved in ''N. abietis'' outbreaks are increased immigration, female-biased sex ratios, and reduced mortality due to diseases, parasitoids and host-plant effects.G. Moreau, D.P. Ostaff, É. Bauce, E.S. Eveleigh, C.J. Lucarotti, B. Morin, and D.T. Quiring (2018) Interlacing roles of bottom-up, top-down, endogenous and anthropogenic factors in population oscillations. Ecosphere 9: e02421.G. Moreau (2004). The influence of forest management on defoliator populations: a case study with Neodiprion abietis in precommercially thinned and natural forest stands. PhD dissertation, University of New Brunswick, Fredericton, New Brunswick, Canada.G. Moreau, E.S. Eveleigh, C.J. Lucarotti, and D.T. Quiring (2006). Ecosystem Alteration Modifies the Relative Strengths of Bottom-up and Top-down Forces in a Herbivore Population. Journal of Animal Ecology. 75: 853–861.G. Moreau, E.S. Eveleigh, C.J. Lucarotti, B. Morin, D.T. Quiring (2017) Opposing effects of mortality factors on progeny operational sex ratio may thwart adaptive manipulation of primary sex ratio. Ecology and Evolution 7(13): 4973–4981. The outbreaks of the balsam fir sawfly cause a reduction in tree growth which in turn can cause tree mortality.H.D. Piene, D. Ostaff, E.S. Eveleigh (2001). Growth loss and recovery following defoliation by the balsam fir sawfly in young, spaced balsam fir stands. The Canadian Entomologist 133:675–686.D.P. Ostaff, H. Piene, D.T. Quiring, G. Moreau, J.C.G. Farrell, T. Scarr (2006). Influence of pre-commercial thinning of balsam fir on defoliation by the balsam fir sawfly. Forest Ecology and Management 223:342–348. The balsam fir sawfly, more specifically third to fifth instar larvae are responsible for

defoliation A defoliant is any Herbicide, herbicidal chemical sprayed or dusted on plants to cause their Leaf, leaves to fall off. Defoliants are widely used for the selective removal of weeds in managing croplands and lawns. Worldwide use of defoliants, ...

and foliage weight loss in trees. Balsam fir sawfly defoliation does not stimulate the release of buds or shoots, which contributes to a slow recovery and severe impact on the balsam fir. ''N. abietis'' outbreaks have been documented to increase in intensity in thinned forests of Atlantic Canada.G. Moreau, E.S. Eveleigh, C.J. Lucarotti, D.T. Quiring (2006). Stage-specific responses to ecosystem alteration in an eruptive herbivorous insect. Journal of Applied Ecology 43: 28-34.G. Moreau, D.T. Quiring (2011). Stand structure interacts with previous defoliation to influence herbivore fitness. Forest Ecology and Management 262: 1567-1575. Balsam fir outbreaks can be shortened by the application of a

baculovirus ''Baculoviridae'' is a family of viruses. Arthropods, among the most studied being Lepidoptera, Hymenoptera and Diptera, serve as natural hosts. Currently, 85 species are placed in this family, assigned to four genera. Baculoviruses are known ...

known as nucelopolyhedrovirus (NeabNPV),G. Moreau, C.J. Lucarotti, E.G. Kettela, G.S. Thurston, S. Holmes, C. Weaver, D.B. Levin, B. Morin (2005). Aerial application of nucleopolyhedrovirus induces decline in increasing and peaking populations of Neodiprion abietis. Biological control 33: 65-73.G. Moreau, C.J. Lucarotti (2007). A brief review of the past use of baculoviruses for the management of eruptive forest defoliators and recent developments on a sawfly virus in Canada. The Forestry Chronicle 83: 105-112. which has been shown to be involved in the natural decline of balsam fir sawfly outbreaks. NeabNPV works by infecting the epithelial cells of the larvae midgut, this infection can be carried within the midgut through to adulthood.C.J. Lucarotti, H.W.W Beatrixe, R. Lapointe, B. Morin, D.B. Levin (2012). Pathology of a Gammabaculovirus in Its Natural Balsam Fir Sawfly (''Neodiprion abietis'') Host. Journal of Entomology. 2012: 1-13. Neemix, an insect growth regulator has also been used to slow down larval and pupal development by decreasing pupal weight, and can reduce the ability of the adults to emerge from their cocoon.S.Y. Li, A.C. Skinner, T. Rideout, M.D. Stone, H. Crummey, and G. Holloway (2003). Lethal and Sublethal Effects of a Neem-based Insecticide on Balsam Fir Sawfly (Hymenoptera: Diprionidae). Journal of Economic Entomology. 96(1): 35-42.

References

{{Taxonbar, from=Q14452972 Tenthredinoidea Hymenoptera of North America Insects described in 1841