Lepidoptera classification

Current classifications (e.g., Kristensen, 1984) divide the order Lepidoptera into four suborders, with the most advanced of these, the suborder Glossata, containing more than 99 per cent of all Lepidoptera. The suborder Glossata is characterized by the presence of a coiled tongue (technically a haustellum) for sucking nectar that is generally associated with butterflies and moths; this group (except for a few very primitive families) also has hollow wing scales, believed to make them more aerodynamic. The other three suborders of Lepidoptera (Zeugloptera, Aglossata, and Heterobathmiina) have primitive chewing mouthparts, like those of caddisflies, and have wing scales that are solid. Each of these three suborders contains a single family, with most species confined to southern South America, Australia, and New Zealand. The most primitive of these families, the Micropterigidae in the suborder Zeugloptera, has a number of species that occur in the Northern Hemisphere, including two species in Canada.

The suborder Glossata is arranged in four groups called infraorders in which, as in the three suborders described above, 99 per cent of the species belong to the most highly derived group, the infraorder "Heteroneura," and the remaining three groups are small and primarily distributed in the southern continents. The term "Heteroneura" means that the veins in the hindwing are reduced in number, and are different in pattern, from those of the forewing; the forewing and hindwing are also usually very different in shape. This infraorder is also called the "Frenatae," because there is a lobe, or spine (frenulum), on the leading edge of the hindwing that holds it in place underneath the forewing; the more primitive suborders and infraorders have a structure called a "jugum," which is a lobe near the base of the hind margin of the forewing that holds it in place above the hindwing.

The Heteroneura (Frenatae) contains the butterflies and most of the families of moths in Canada. The best known of the more primitive infraorders are the Ghost Moths (family Hepialidae in the infraorder Exoporia), which includes 13 species in Canada. A subset of the Heteroneura is called the Ditrysia. The families in the Ditrysia have two separate sexual openings in the female, one for mating and the other for egg laying; the more primitive families are collectively called the "Monotrysia" and have only a single sex opening. An anomaly that still puzzles scientists is that the Ghost Moths (infraorder Exoporia), which lack the fundamental characters of the infraorder Heteroneura, have a "ditrysian" type of female reproductive system that is remarkably similar, if not homologous, to that found in the "higher" heteroneuran families (i.e., the Ditrysia). The Ditrysia includes about 98 per cent of the 6,500 species of butterflies and moths in Canada.

The largest and most familiar group in Ditrysia is called the Macrolepidoptera. In Canada the Macrolepidoptera is a group of six superfamilies of Lepidoptera: Hesperioidea (skippers), Papilionoidea (true butterflies*), Geometroidea (mainly inchworms and loopers, family Geometridae), Mimallonoidea (sack bearers), Bombycoidea (mainly giant silk moths, family Satumiidae, tent caterpillars, family Lasiocampidae, and sphinx moths, family Sphingidae), and Noctuoidea (mainly cutworms and armyworms, family Noctuidae, tiger moths, family Arctiidae, and tussock and gypsy moths, family Lymantriidae). Some workers (e.g., Brock, 1971) suggest that the Macrolepidoptera is mainly a grouping of convenience combining families that share a larger size and increasing fusion of adult and pupal structures but do not necessarily share a common ancestry. More recently, Scott (1986) and Minet (1991), using mainly details of shape and structure of the sclerites at the wing bases, have suggested that the Macrolepidoptera do share a common ancestry.

Which family of moths in the Macrolepidoptera is most closely related to butterflies has been a topic of speculation and debate for more than a hundred years. The most compelling evidence to date suggests that butterflies are related to the family Hedylidae (Scoble, 1986; Scoble and Aiello, 1990; Minet, 1991), a family of Neotropical moths once thought to be in the family Geometridae but now placed in a superfamily of their own (i.e., the Hedyloidea).

* A term used for members of this superfamily to distinguish them from the skippers; members of both superfamilies are "butterflies."

Reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.