Excerpt from Eighty·Sewnd Annual Report
of the
Entomological Societ)
of Ontario - 1951
COCOONS OF SOME SAWFLIES THAT DEFOLIATE FOREST TREES
IN MANITOBA AND SASKATCHEWAN'
H. R.
WONG"
Laboratory of Forest Biolo&'Y
Winnipeg, Manitoba
l:-':TRonUCTIO:-':
This research was 'lndertaken to estimate the value of cocoons as a criterion for the de·
terminat',on of the families and genera of sawflies that defoliate forest trees in Manitoba and
Saskatchewan. The study was mainly confined
10 those insects actually reared by the author.
()bservations of �I, large number of sawflies reared indicate that the shape and texture of cocoons
ale generally constant for a given species. However, in both natural and artificial environments,
the shape and texture may be modified by the amount of food, humidity, temperature, and by
weakening far:tors such as parasitism.
Several writers have described sawfly cocoons and noted their habitats.
MacGillivray
(1913)
has repnfted the method by which a nUlllber of sawfly larvae prepare for pupation. Rohwer and
:\Iiddleton (1922) have described cocoons of several species of the tribe Cladiini. Frost (1925 gav'c
an account on the cocoons and hahitats of many leaf·mining sawflies.
Schaffner and -'Iiddleton
\1950) puhlished similar information on the most common forcst sawflies. In Europe, some of the
characteristics of sal\'Hy cocoons of a number of species hav'e been given by Balachowsky and
Mesnil
(1935·1936) and Enslin
(1912·1918).
The descriptions of sawfly cocoons are generally
meagre, and literature on the identification of sawfl)' cocoons to family or genus is apparently
absent.
GE:-':ERAL CHARACTERISTICS OF S.lWFl.Y COCOO:-.:S
The cocoons of sawflies that defoliate forest trees are made of silk, or silk with soil, sand,
leaves, twigs, frass, etc.,
incorporated with them.
Their texture is generally leather·like
relatively thick·walled, opaque, and usually polished) or parchment·J,ike
structed, thin·walled, polished or dull, and lIlay
be translucent). Csually the cocoons ha\'e one
:\ normally single·walled cocoon
or two walls, with or without small openings in the outer wall.
will be double·walled if it (:ontains a larva of an ichneumonid parasite.
sfcond "all is of a vcry thin parchment·like material
cocoon of Pristiphom erichsonii
flattened,
irregularly oval,
!firm,
(flexihle, loosely con·
(e.g,
In such cases, the
Mesoleius tellthredillis Morley, in
(Htg.) ). The cocoons may be of v-arious shapes; they may he
ellipsoidal,
or tapered at one end.
Their surface
roughened, with the interior generally polished and smoother than the exterior.
is smooth or
Many species of sawflies that attack forest trees pupate in earthen cells or in rotted wood.
Species of Acantholyda, Cephalcia, Neurotoma, Telltilredo, Rhogogastn', Empria
and some AmaZlronematus, pupate in earthen cells in the ground.
(Pamtaxollus)
These earthen cells are
covered inside with silk or glue which forms a polished surface. On the other hand, species of
Allantus, Macremphytlls, Nematus (Pol/lallia) pupate in rotted \\'ood or make thin parchment·
like c�coons in wood,
COCOONS OF OTHER INSECTS
Cocoons formed hy some ILepidoptera
(e.g., Tetralopha asperatella
(Clem.), ]'\I[l')'oplt'm pra·
vella (GrL), and Schizu)'{l lej)til/oides (GrL) ) and some hymenopterous parasites resemble those
of sawflies with which they lIlay be easily confused.
semble those of sawflies
'Contribution
Ottawa, Canada.
No.
31,
Generally, lepidopterous cocoons that reo
arc not leather·like, but more of a
Division of
2Agricultural Research Officer.
Forest Biology,
wool·like
Science Servi<;e,
consistency.
Department
of
Coarse
Agriculture,
G2
REPORT OF THE EYfOMOLOGICAL
silken strands
or silken strands of irregular texture usually found on the surface of sawfly
cocoo[>s, are generally absent in the Lepidoptera "'hich form a cocoon
(Fig.
I).
If the lepidoptc­
rous cocoon is of thin parchment-like material, the ohtected pupa; case of the 1110th can be
seep within the structure
(Fig. 2).
3
1
2
4
6
5
7
9
8
•
10
12
11
10MM
Fi g.
1-10 and 1:1; dorsal
I/oidl's
(j.
(Grt.).
.J.
,ie\\'
/)IlS0I/a
TrichiosOIIl(l Iriallgllll1l11
/":elliceps (Cress.).
9.
of COCOOIl.
(I'rm.).
viril/a
Khy.
i.
I.
r('/m/ol,/ta asl'(,fIIlrl/a
I.
(Roh.).
Fig.
'p.
5.
(C1CIlI.). :1. S,./ijwra
"Jrg<'
;V{'()(iijniol/ (/I//('ricalllls IWl/hilll/(,,,
Prioplwrus j)(Iilipes (Lep.).
alaskensis
I'/IOi/o""l/jll:
II;
II).
IIl'c/ora/is
Rob.
�.
Prislij,hora erichsol1ii (Htg.).
end view of cocoon.
A mauronemaius sp.
"'I,li.
(Leach).
j\[olloclclIlI.\
12. Pikollellla
63
SOCIETY OF ONTARIO
The cocoons of parcsiles that resemble sawflies are generally more tapered at both ends
(Fig. "). In some parasitic species, however, the cocoon is not so tapered, but a light-ringed area
is present in this centre
(Fig.
4).
This ringed area is present and visible also in some. newly
formed sawfly cocoons, but it later disappears as the cocoons take on a darker hue. The surface
of parasitic cocoons is generally smooth compared with the roughencd surface of many sawfly
cocoons.
Cocoons of some parasites are also composed of a thin, transparent, parchment-like
material, but the enclosed parasitic larvae can be easily distinguished flom sawfly lanae.
SPECIFIC CH.\R.\CTERISTICS OF COCOc)::\S .\CCORDI::\G TO F.\�!ILIES
In this paper, the classification of sawflies follows that adopted by Ross
Ries, M1ddlekauf and Stannard
(1951).
(1937).
and Ross,
Those sa\':flies which construct cocoons. and which de­
foliate forest tr!':!s, belong to the families Argidae. Cimhicidae, Diprionidae, and Tenthredinidae.
The following is a description of the cocoons of gel)cra and species of these families. reared by
the allthor.
ARGlDAE
In this famil), Arge is the only genus associated with forest trees. The cocoons are roughly
oval with double walls (Fig.
S).
The outer ,vall is dUll, and is either netted or has small irre­
gularly spaced opf'nings on the sides.
The inner wall is dull parchment-like, and may be either
separated from or adhering to the outer wall.
Colour buff to brown.
Length
1'0-15
mm.
Hosts of species reared: birch, hawthorn, willow. poplar. alder, rose, and cherry. Cocoons are
spun in leaf littr.r on the ground.
Species reared:
."1. jNctoralis (Lcach) and A. clallicornis (F.).
CIMBICID,'lE
The cocoons arc generally single-walled. shining, leather-like, and cylindrical "'ith rounded
ends
(Fig.
6).
If the cocoon is dissected, it partial second wall may sometimes he present.
second wall is Illore eddent in cocoons of Zaraea.
22 mm.
Colour reddish-brown to black.
This
Length
13-
Hosts of species reared: willow, poplar, honeysuckle, cherry, alder, birch, ellll, and
saskatoon. Cocoons are generally constructed in leaf litter and topsoil. Species reared: Zaraea
in/iata :\ort., Z. americana Cress. . Trichiosoma triangulum Khy., awl Cim/nx americana amer
irana Leach.
DIPRlONlDAE
NeodijJrion and Monoelcuus ,,'ere the only genera reared in :\fanitoha and Saskatchewan.
Cocoons of Diprioll, including its subgenus (;iijJinia, reared in Eastern Canada, were also ex·
amined.
The cocoons are single-walled, leather-like, shining, and ellipsoidal
(Fig.
7).
The only
e',(ccption is found in Monoctelllls, where the cocoons have double "'alls and are not shining.
The outer "'all is loosely constructed of coarse silken strands, "'ith particles of earth adhering
'
LO it; the inner wall is leather-like" shining, and cylindrical with rounded ends (Fig. 8). The
only significant difference notetl between the genera with single-walled cocoons is that cocoons
of D!prioll similis
reddish-brown.
(Htg.) appear to he more robust and have thicker walls.
Length
6-12
mm.
Hosts of species reared:
Colour buff to
pine, spruce, cedar, and juniper.
Cocoons are constructed among the needles on the twigs, and in lilter and topsoil.
Cocoons
MoriOelenus were formed usually in the soil. Species reared: Neodiprion abietis (HalT.),
N. swai))ei Midd., N. na/wlus Schedl, N. americanus banksianae Roh., N. virginiana Roh.,
N. amaieall11S dyari Roh., and M01l0ctemlS mellieeps (Cress.).
of
TENTHREDINIDAE
Cocoons of the Tenthredinidae, which is the largest family of sawflies, showed the greatest
\' ariation in shape,
texture, colour, size, and habitat.
Unlike those of the other families, the
larvae of Tenthredinidae feed on either deciduous or coniferous trees.
Cocoons in the genera
Nematlls and A mallrDllematlls may be single- or douhle-walled as explained in the following
pages.
REPORT OF THE ENTOMOLOGICAL
The species of the tribes Nernatini and Cladiini of the subfamily Nematinae cause the greatest
damage to forest trees. Cocoons of the tribe Cladiini are easily recognized by their irregular
oval shape and paper-thin walls, which are transparent or semi-transparent. Walls may be single
or double according to the genera and species. These cocoons are about 8-14 mm. long, light­
brown to brown in colour and are usually attached to a leaf such as birch, willow, cherry, saska­
toon, or to Jbjects such as the rearing jar (Fig. 9). Species reared: PriojJhorus pallipes (Lep.).
It is in the tribe Nem·ltini that the cocoons show the greatest variation. The following de­
$uiptions are of cocoons of the more comllLQn genera.
NEMATUS (PTERONIDEA) Rohwer
Cocoons may be dull or shining, flattened, irregularly oval, cylindrical with rounded ends,
or tapered at one end. Cocoons may be made of a leather-like or parchment-like material with
single or double walls. If single-walled cocoons are dissected, a partial second wall may be
present as in Cimbicidae. The walls of some cocoons have earth incorporated or adhering to
them. Flattened and irregularly oval cocoons are usually parchment-like, semi-transparent, or
opaque, often with heavy silken strands on the sides. Cylindrical cocoons like N. hyalinus
(MarL) are usually leather-like and opaque; those with double walls like N. possibly chalceus
(Marl.) may have small openings in the outer wall at one or both ends. Cocoons with one end
tapered may be made of either parChment-like or leather-like material. Colour: yellow, light­
brown, brown, dark-brown, or reddish-brown. Length 7-14 mm. Hosts of species reared: willow,
poplar, birch, maple, alder, and gooseberry. Cocoons are formed between leaves, next to the
gla�s of the rearing jar, in litter, between litter and soil, and in soil. Species reared: N. pingui­
dorsum Dyar, N. mendicus Walsh, N. limbatus Cress., N. hyalinus (MarL), N. ribesii (Scop.),
N. possibly chalceus (MarL), and several species of unidentified N. (PteTOnidea).
NEMATUS (PONTANIA) O. Costa
Cocoons of species reared have single walls. They are shining, leather-like or parchment·
like, cylindrical, with rounded end,. The leather-like cocoons resemble those of Pristiphora (as
explained bel')w), but are smaller. Colour brown or dark-brown. Lenth 5-6 mm. Hosts of
�pecies reared: poplar and willow. Cocoons are constructed between lea\'es, on leaves, within
a folded leaf, between litter and topsoil, and in �oil. Cocoons formed in rotted wood or in
galls are generally thin and parchment-like. Species reared: N. bozelllalli (Cooley), and N. (PO I l ­
(allia) spp.
.,L'\!OPl.ONYX Marlatt
Cocoons are dull, cylindrical, with double walls. Soil, leaves, and litter are bound to their
(luter wall. The outer wall is not readily discernible in some cocoons realed under artificial
conditions; loose silken strands, however, are generally on the surface, especially at both ends
of the cocoon. The inner wall is shining, parchment-like. Colour light-brown to brown. Length
6·� mm. Host of species reared: larch. Cocoons are formed in litter or het ween littel and
topsoil. Species reared: A . luteipes (Cress.) and A. occidens Ross.
PRISTIPHORA Latreille
Cocoons are leather-like, shining, single-walled,cylindrical, with rounded ends. Coarse silken
strands are usually found on the surface of coccons (Fig. 10). Colour generally dark-brown.
Length 6-12 mm. Host of species reared: lalch, birch, spruce, and willO\\r. Cocoons are formed
between leaves, in litter and soil, and in soil. Cocoons of P. erichsonii (Htg.) are sometimes
formed in old emerged cocoons. Species rear�d: P. erirhsonii (Htg.), P. sycojJhanta Walsh, and
Pristiphora spp.
AMAURONElI1ATUS Konow
Cocoons may be dull or shining, flattened, irregularly oval, cylindrical, with rounded ends,
or with olle end tapered. They are generally single-walled with the texture either parchment­
like or leather-like. Soil adheres to or is incorporated with the walls of some cocoons. If the
SOCIETY OF ONTARIO
cocoon has a double wall, it is usually parchment-like.
istics of single-walled cocoons is the presence of
(Fig_
11).
3
to
25
65
One of the distinguishing character­
pores at one or both ends of the cocoons
A partial second wall may also be present in some cocoons of this genus.
light-brown, brown, or reddish-brown.
!Arch, alder. and oak.
Length
6-13
Colour:
mm. Hosts of species reared: willow, poplar,
Cocoo·'.s are constructed between leaves, in litter, between litter and
topsoil, and in soil. Some species of this genus do not construct cocoons, but form earthen cells
Jl1 which to pupate.
Because of the need for revision or the genus, no attempt was made to
identify the various species of AmallTOllematllS reared.
l'IKONEMA Ross
Cocoons are single-walled, more or less shining, elongate, with one end rounded and the
other end tapered to a blunt point. Several layers of silken strands are present at the pointed
end of the cocoon.
(Fig.
12).
Coarse silken strands are usually e\·ident on the surface of the cocoon
Some cocoons may have soil, [rass, or leaves adhering to them.
to bll'Ck. Length
9-11
mJlll.
Host of species reared:
Colour dark-brown
spruce. Cocoons are formed in litter and
lopsoil, in soil. and between the needles on the twigs. Species reared: P. alaskellsis
(Roh.), and
P. dimmockii (Cress.).
NEMATINUS Rohwer
Cocoons are cylindrical with double walls.
The outer wall is dull, loosely constructed of
coarse silken strands with earth and sand incorporated and adhering to it.
shining and leather-like. Colour brown. Length
form cocoons in the soil.
8-9
The inner wall is
mm. Host of species reared: birch.
Larvae
Species reared: N. llnirolor (:\iarl.)
CROESUS Leach
Cocoons are single-walled, shining, irregularly oval, rounded at one end and tapered at the
other.
Lo(>se, silken strands are evident at the pointed end.
or black.
Length
9-11
Colour very dark reddish-brown
mIY!. Host of species reared: birch. C.. ocoons constructed between litter
and soil, and in soil. Species reared: C. latitarsliS Nort.
ILATYCAMPUS Schiodte
The outer wall is dull, made of coarse silken
Cocoons are cylindrical, with double walls.
stral'ds with soil incorporated and adhering to it; the inner wall is shining, more leather-like
than parchment-Jj\e.
Colour brown.
Length
7
mIll.
fO"med in the soil. Species reared: P. alllericanlls
Host of species reared: poplar.
COCOOIlS
(Marl.).
HEMICHROA Stephens
Cocoons are dull, irregularly o\'al, and douhle-walled.
The outer wall is composed of silken
strands with earth and sand incorporated and adhering to it;
ment-like. Colour brown. Length
10-12
the inner wall is thin and parch­
mm. Host of species reared: alder. Cocoons constructed
in the earth, between litter and soil. Species reared: H. crocea (Fourc.).
KEY TO SEPARATE THE PRECEDING FAMILIES
I.
Cocoons with single wall (Figs. 6, 7, 10)
Cocoons with double wall (Figs. 5, 8)
2.
Cocoons made of parchment-like material
Cocoons made of leather-like material
3.
Cylindrical with rounded ends ................................ .
Not cylindrical, flattened, or with one end tapered (Fig.
4.
3-25
2
7
(Fig.
small opening at one or hoth ends (Fig.
No small openings at one or both ends .
9)
II)
Tenthredinidae
12)
(In Part)
3
4
Tenthredinidae (In Part)
Tenthredinidae (In Part)
5
REPORT OF THE .E.NTOMOLOGICAL
66
:).
Leng;th I�I mm. or ()\'er (Fig. 6)
Length under 13 mm.
!)
6
:\0 heavy silken �trands on surface; without earth incorporated into make-up of cocoon;
mer 6 mm. in length (Fig. 7)
Diprionidae (except Monoctel1us).
Heavy. dark silken strands on surface (Fig. 10); or with earth incorporated or adhering to
cocoon; or less than 6 mm .. in length
Tenthredinidae (In Part)
7. Outer wall of cocoon netted or with small openings on sides (Fig. 5)
Argidae (Arge)
Silken strands of outer \\"all of cocoon criss-cross (Fig. 8), or without small openings on sides,
8
with or without earth inoorporated or adhering to outer wall
fl.
Outer wall of cocoon without small openings on side; if silken strands of outer wall criss­
cross, not associated I"ith cedar or juniper
Tenthredinidae (In Part)
Silken strands of ollter wall of cocoon criss-cross, associaled \\"lth cedar 0" juniper
Diprionidae (Monor/emls)
(FIg. R)
DISCUSSION
In this paper an 'illempt has been made to characterize the main families of sawflies that
defoliate forest trees in :Vlanitoba and Saskatchewan. by the slUdy of the species which spin
a COCOOI].
Though only a limited number of species \I'ere examined and many of these were
lea"ed under artificial conditions, the results show that cocoons within the families Argidae,
Cimbicidae, and Diprionidae (excepting the genus MOlloclellus), are constant as to shape and
texture. On the other hand, cocoons of the family ,Tenthredinidae are variable. However, in
the HlbfaU1ily Nematinae, cocoons of the tribe Cladiini appear to be constant. They are variable
ill the tribe Nematini, except in the genera Pristiphora, A llopionyx Pikollema. and Nematlls
(Polltallia), \I'here they appear to be constant when the cocoons are formed in litter and soil.
Though seyeral cocoons of only one species were examined in the genera Croeslls, Helllicilroa,
P':atycamplIs. and Nelllatillus, their shape and texture also appears to be stahle. The greatest
Yarialions were found in the genera Nonalus, and Amaurollemalus.
It is interesting to note that in the case of Pristiphora, the texture and shape of the cocoon
constructed by I;-nae feeding on deciduous or coniferous trees \I'ere the same. The shape of the
cocoon Idll be influenced by its position in its habitat. \Vhen laryae use the surface of leaves,
twigs, or rearing jars for spinning their cocoons, heavy silken strands do not occur on that side
of the cocooning surface. The basal shape of the cocoons will generally conform to the shape
of the surface on which the cocoon is spun.
:Ellyironlllental conditions Illay also influence the texture and colour of the cocoon. For
example, cocoons forllled in a dry mediulll are more lightly coloured than those formed under
moist conditions.
Cocoons of sawflies of different families are often similar in shape and texture. However,
distinguishing characteristics in habitat, host, colour, and size, permit their classificatioll into
tilen rcspecti\'e families.
ACKNOWLEDGMENT
The ,\Titer is indebted to Drs. O. Peck and R. Lambert of the Systematic Unit, Diyision of
Fntomologl' for their suggestions and advice in the preparation of this paper.
REFERENCES
et 1,. :\f!·:S:\LI. 1935-1936.
sements Busson, Puris.
BALACHO\\'SKY, A.
Les insectes nuisibles aux plantes cultin'es. Etahlis­
E;-,;su:\, E. 1912-1918. Die Tenthredinoidea :'Ifitteleuropa. Beihefte der Deutsche Entomologische
Zeitschrifl. Berlin.
FROST.
S. W. 1925. The leaf mining habit in the Hvmenoptera. Ann. Ent. Soc. Amer. 18: 399-416.
A. D. 1913.
Soc. Ont. 4·1: 54-75.
l\IAcGn.l.IVRAY.
The immature stages of the Tenthredinoidea. Ann. Rept. Enl.
SOCIETY OF ONTARIO
:\il/)[)LETO�,
W.
67
19:?2.
S. A.. and W. MIDDLETON. 1922. :>iorth American sawflies of the suhfamily. Cladiinae.
"otes on habit,; and descriptions of larne. Proc. U. S. "atl. ;\[us. 60: I·-I{i.
ROHWER,
Ross, H. H. 1937. A generic c1assificatioll of the :'-:earctic sawflic, (Hymcnoptcra. Symphyta).
111. BioI. Monogr. 15. :'-:0. 2.
Ross, H. H.. D. T. R I��� , W. \V. :\[U)[)LEKAUF, and L. J. STANNARn. 1951. Suhorder SYlIIplnta
(Chal;.stogastra). III Mucscbeck. C. F. W., K. V. KROMBEIN, and H. K. T()\\,�ES, Hymenoptera
of America :\orth of Mexico. l; .S. ))<:pt. .\gr. \,!onogr. :'-:0. 2. -\·89.
.
J. V., Jr., and W. Y!IDDLETO"i. 1950. Suborder Chalastogastra or Symphyta. III
Craighead, F. C., Insect enemies of eastern forests. U.S. Dept. Agr. Mise. Pub. 657: 5�2·591.
ScHAFFNER,
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