|Lab 8: Trichoptera
Order Trichoptera (Caddisflies)
Trichoptera means “hair-wings” which describes the hairs present on the wings of the adults and care commonly called Caddisflies. Trichoptera are closely related to Lepidoptera (share the same common ancestor); Lepidoptera have scales on their wings rather than hairs.
Caddisflies are well-known for the wide diversity in their use of silk for building nets or cases. The larvae of Limnephiloidea (tube-case builders) will often build cases out of any material in their habitat and often have strict requirements on the size or type of material used. Larvae which use plant material will often cut the material to the necessary size; larvae which use mineral materials will often search and select material to fit the case exactly.
Head capsule subdivided into three parts by Y-shaped dorsal ecdysal lines (sutures). Body generally only sclerotized on the head, thorax, and on the dorsum of abdominal segment IX. Eruciform (caterpillar-like) body; abdomen usually enclosed in a case made of stones, leaves, twigs, or other natural materials. Head capsule well-developed with chewing mouthparts. Thread-like abdominal gills usually present in case-makers. One pair of hooked prolegs often present at tip of abdomen bearing claws.
Immatures generally fall into 5 categories based on case or net-building strategy. These five categories can be grouped under the superfamily designations:
net-spinners or retreat-makers
Filiform antennae. Mouthparts reduced or vestigial. Two pairs of wings clothed with long hairs. Wings held tent-like over the abdomen.
Terms to know:
notal setae (sa1, sa2, sa3)
A note about larval antennae:
generally very hard to see
, often can’t see them at all except under high magnification except
in the family Leptoceridae (diagnostic character for the larvae).
Families to know:
Diagnostic characters for larvae: ( ) matches statement in M&C (1996) key
(1) anal claw comb-shaped
– case coiled and shaped as a snail-shell
(2) all three thoracic segments are sclerotized
– has ventrolateral gills on the abdomen
(4) has long antennae
(5) mesonotum is entirely membranous
(6) abdominal segment IX has sclerite on dorsum
Phryganeidae – prosternal horn present
Glossosomatidae – anal proleg broadly joined w/abdominal segment 9
Rhyacophilidae – anal proleg free from abdominal segment 9
(6’) abdominal segment IX with dorsum entirely membranous
– T-shaped membranous labrum (often retracted)
– trocantin of foreleg broad and hatchet-shaped
(5’) mesonotum covered by sclerotized plates
(13) abdominal segment I without humps
(13’) abdominal segment I always with lateral humps
– 16 long setae on center part of labrum
(17) prosternal horn absent; antennae close to anterior margin of head capsule
– 30+ setae posteromesad of lateral sclerite on anal
– 3-5 setae posteromesad of lateral sclerite on anal proleg
(19) median dorsal hump of abdominal segment I lacking, antennae close to
anterior margin of eye
(19’) median dorsal hump of segment I present, antennae midway between
anterior margin of head capsule and eye
– anteromesal border of mesonotum emarginate