About sawflies

 

Adult female Diprion similis ovipositing eggs on a pine needle

 

Neodiprion eggs laid in a row along a pine needle

 

Neodiprion larvae feeding gregariously

 

diprionid cocoons (Neodiprion sertifer)

Examples of an ovipositorovipositor:
the female organ that deposits eggs and is used to drill into plant tissue, located at the apex of the abdomen, made up of the lance and lancet
“ sawsaw:
ovipositor
”, the egg-laying apparatus of the female sawfly:

 

classically saw-like ovipositor (Pristiphora genticulata)

 

long, thin ovipositor used for drilling into wood (Sirex nitidus)

 

 

rounded ovipositor (Cimbex sp.)

 

full ovipositor mounted separately to see the specific segments

 

Trichiosoma triangulum pair mating

 

Syntexis libocedrii female ovipositing into wood

The active immature stage in sawflies is the larval stage. LarvaeLarva:
the immature stage of holometabolous insects
are morphologically distinct from adults. In sawflies, the larvaelarva:
the immature stage of holometabolous insects
are generally caterpillar-like with visible sclerotizedsclerotized:
hardened, rigid
heads, sclerotizedsclerotized:
hardened, rigid
legs attached to the thoraxthorax:
the second and middle segment of the body, between the head and abdomen
, and fleshy prolegs on their abdomenabdomen:
the third and last segment of an insect's body; in sawflies this is usually made up of 11 segments (segments 9 and 10 often fused)
. The larvaelarva:
the immature stage of holometabolous insects
of leaf-mining and wood- or stem-boring taxa, as well as the Pamphiliidae, frequently have reduced or absent legs and prolegs. Like all insects, transitions between life stages occur during a molt. This includes multiple larval stages, or instars, with between five and nine instars across the group.

 

caterpillar-like sawfly larva with a sclerotized head capsule and developed thoracic legs (Trichiosoma triangulum)

 

leaf-mining sawfly larvae with reduced legs and head capsules

 

woodwasp larva with clear body segments but without clear head capsule and with a short horn at the apex (Sirex noctilio)

 

“slug” sawfly larva with less developed legs and indistinguishable abdominal segments (Caliroa sp.)

The pupal stage occurs during metamorphosis from larvalarva:
the immature stage of holometabolous insects
to adult. PupaePupa:
the intermediate and inactive life stage of holometabolous insects, between larva and adult
are largely immobile, and look somewhat like a mummified version of the adult. Legs, wings, and other adult body parts are visible, but are pressed closely to the body and mostly immoveable.

 

Sirex noctilio pupae

Adult sawflies are generally winged, and most species have two sexes. Body form varies widely, from stout, hairy, and bee-like, to long, slender, and wasp-like. Many species have aposematicaposematic:
having warning coloration, indicating that an insect is unpalatable or venemous or otherwise dangerous
coloring and look like their venomous cousins, wasps. While some sawflies can deliver a jarring bite, no species of sawfly can sting.

 

sawfly with formidable jaws (Trichiosoma triangulum)

 

sawfly with a scary-looking “stinger” that is actually a non-venomous ovipositor (Tremex columba). Photo: Nathan Schiff, USDA FS

 

sawfly exhibiting aposematic coloration (Tenthredo sp.)

Feeding Behavior

Sawflies do most of their feeding during their larval stage. Nearly all sawflies feed on plants, in almost every fashion imaginable. Most are external leaf feeders, but many are internal wood borers, stem borers, gall formers, leaf rollers, or leaf miners. Many taxa are characterized by a consistent feeding behavior within their group. For example, most Heterarthrinae in North America are leaf miners, while Siricidae are all wood borers. Wood-boring larvaelarva:
the immature stage of holometabolous insects
(Siricidae, Xiphydriidae, Anayelidae) are associated with fungal symbionts, which are usually transmitted by ovipositing sawflies. The fungi attack the host plants, and facilitate wood digestion by sawfly larvaelarva:
the immature stage of holometabolous insects
or become food themselves. Many sawfly genera are specialists or narrowly oligophagous, feeding only on a single or limited number of plant species. Several genera have diversified in association with a single group of plants, such as Neodiprion on Pinaceae. Other complex groups of closely related genera have diversified across certain plant genera. In North America this is exemplified by the diversity of Nematus, Pontania, and Eurra species associated with willows.

 

web-spinning sawfly larvae feeding among webs of silk, leaf matter, and frass (Neurotoma flaviventris)

 

woodwasp larvae feeding on the interior of a log (Sirex noctilio)

 

willow leaf galls induced by sawfly larvae

 

leaf-mining sawfly larvae feeding on the parenchyma of the leaf, internally

 

“slug” sawflies feeding externally on the parenchyma of an oak tree leaf (Caliroa sp.)

 

stem sawfly larvae feeding on the vascular tissue of a rose stem (Phylloecus trimaculatus)

Sawflies in the subfamily Tenthredininae have been observed feeding on other insects as adults (see page for Rhogogaster and Tenthredo). The only other regularly predaceous sawflies are in the Orussidae, of which some species are parasitoids of wood-boring beetle larvaelarva:
the immature stage of holometabolous insects
(see page for Orussus).

Though no sawflies are social in the sense of eusociality exhibited by many bees and wasps, sawfly larvaelarva:
the immature stage of holometabolous insects
will often feed in aggregations, presumably for defensive purposes. Larval defensive behavior also includes coordinated movements, such as the jerking behavior exhibited by Neodiprion sertifer larvaelarva:
the immature stage of holometabolous insects
and the toxic compound excretion exhibited by some Arge species.

external feeding sawfly larvaelarva:
the immature stage of holometabolous insects
exhibiting defensive “twitching” when they sense nearby movement (Neodiprion sertifer)

 

external feeding sawfly larvae in the characteristic “S” body shape, often a defensive position