British Insects: the Families of Trichoptera

DELTA Home

L. Watson and M. J. Dallwitz

Character List

#1. <Synonyms:>/

Adults.

#2. Adults <whether minute>/

1. minute <fore-wings up to 4 mm long>/

2. not minute <fore-wings more than 4 mm long: implicit>/

#3. Adults <whether black>/

1. black/

2. not black/

#4. Antennae <relative length>/

1. much shorter than the fore-wings/

2. about as long as the fore-wings/

3. considerably longer than the fore-wings/

#5. Antennae <thickness>/

1. stout/

2. slender/

#6. Antennae <relative length of the first segment>/

1. with an elongated first segment <this at least as long as the head>/

2. with a short first segment <this shorter than the head>/

#7. Ocelli <presence>/

1. present/

2. absent/

#8. Maxillary palps <number of segments>/

segmented/

#9. The maxillary palps of males <number of segments>/

segmented/

#10. Maxillary palps <whether filiform>/

1. filiform, with cylindrical segments/

2. thick/

#11. The terminal segment <of the maxillary palps, constitution and relative length: see Notes>/

1. flexible, multi-articulated, annulated and generally relatively elongated <often longer than all the other segments together>/

2. inflexible, not multi-articulated, not annulated, and not much elongated/

This pseudo-character, representing several potentially useful characters, is employed with minor variations of wording at an important, early stage in three influential keys to the families: one for British Trichoptera (Mosely, 1939), one for Australasia (Mosely and Kimmins, 1953), one at world level (Imms, 1957), and another for Australia (Riek, 1970). Comparative data are not provided in family descriptions, nor is the “generally very long, flexible, articulated, annulated” (or whatever) type of terminal maxillary palp segment discussed or illustrated adequately. Furthermore, although the Philopotamidae are always the first family keyed out on the “very long, flexible, articulated” branch, this is clearly erroneous for Chimarra marginata, which is the only British representative on which direct information is to hand (see Curtis’s illustrated description; cf. also the Mosely and Kimmins family description, which hardly conforms in this respect with their key). Persistent reference to the same inadequately described structure, and repetition of the same mistake in keys for different regions, does not inspire confidence in the data compiled here from the same sources.

#12. The mesoscutum <warts>/

1. with a pair of warts/

2. without warts/

#13. The scutellum <warts>/

1. exhibiting a large median wart/

2. exhibiting a pair of warts/

3. without conspicuous warts/

#14. The fringes of the wings <relative length>/

1. longer than the maximum width of the hind-wings/

2. shorter than the maximum width of the hind-wings <implicit>/

#15. The fore-wings <length>/

mm long/

#16. The fore-wings <presence of median cell>/

1. with a <closed> median cell/

2. without a <closed> median cell/

#17. The fore-wings <presence of a discoidal cell>/

1. with a <closed> discoidal cell/

2. without a <closed> discoidal cell/

#18. Apical forks <number exhibited by the forewings>/

#19. The fore-wings <presence of apical fork no. 1>/

1. exhibiting apical fork no. 1/

2. lacking apical fork no.1/

#20. The fore-wings <presence of apical fork no. 2>/

1. exhibiting apical fork no. 2/

2. lacking apical fork no.2/

#21. The hind-wings <width relative to that of the fore-wings>/

1. narrower than the fore-wings/

2. similar in width to the fore-wings/

3. wider than the fore-wings/

#22. The hind-wings <presence of a median cell>/

1. with a <closed> median cell/

2. without a <closed> median cell/

#23. The hind-wings <presence of a discoidal cell>/

1. with a <closed> discoidal cell/

2. without a <closed> discoidal cell/

#24. Apical forks <number exhibited by the hind-wings>/

#25. The hind-wings <presence of apical fork no. 1>/

1. exhibiting apical fork no. 1/

2. lacking apical fork no.1/

#26. Front tibia <number of spurs>/

spurred/

#27. Middle tibia <number of spurs>/

spurred/

#28. Hind tibia <number of spurs>/

spurred/

Larvae.

#29. The larvae <whether constructing a transportable case or a fixed tunnel, or free-living>/

1. constructing and living in transportable cases/

2. constructing fixed retreats of stones and vegetable dèbris/

3. constructing fixed, silken tubes/

4. inhabiting freshwater sponges/

5. case-less and free swimming/

#30. The <free swimming> larvae <whether net-forming>/

1. forming silken nets/

2. not net-forming/

#31. The larval case <structure, molannid type>/

1. shield-shaped, and made of sand grains, with wing-like lateral extensions/

2. not of sand grains and shield-shaped with wing-like extensions <implicit>/

#32. The larval case <structure and shape, whether odontocerid type>/

1. made of sand grains and slightly curved, the hind extremity covered by a dark membrane with a central slit/

2. not made of sand grains and curved, the hind extremity not covered by a dark membrane with a central slit <implicit>/

#33. The larval case <size and shape, whether hydroptilid type>/

1. very small, and seed- or flask-shaped/

2. not particularly small, not seed- or flask-shaped <implicit>/

#34. The larval case <manner of construction, whether phryganeid type>/

1. constructed of vegetable matter arranged spirally, open at both ends/

2. not constructed of vegetable matter arranged spirally <implicit>/

#35. The larvae <general form, campodeoid or eruciform: see Notes>/

1. campodeoid <body dorsiventrally compressed, head not inclined>/

2. eruciform <body cylindrical, head markedly inclined>/

In campodeoid larvae, which seldom construct portable cases, the body is dorsiventrally compressed, and the head is not or only slightly inclined; there is no lateral line, abdominal papillae are lacking, and tracheal gills are often absent.

In the eruciform type, which is associated mainly with portable cases, the body is cylindrical, and the head is markedly inclined; a lateral line is present; retractile papillae (usually one dorsal and two lateral), apparently concerned with maintaining the position of the larva in its case and permitting an even flow of water, are present on the first abdominal segment; and simple filamentous or branched tracheal gills are present on the abdominal segments.

#36. The labrum <of the larva, sclerotization>/

1. sclerotized/

2. not sclerotized/

#37. The right mandible <of the larva, whether bearing a brush of hairs on the inner surface>/

1. exibiting a brush of hairs on its inner (concave) surface/

2. without a brush of hairs on its inner surface/

#38. The thorax <of the larva, presence of a forwardly-directed, prosternal horn>/

1. with a forwardly-directed prosternal horn between the first pair of legs/

2. without a prosternal horn/

#39. The anterior margin of the pronotum <of the larva, extent of sclerotization>/

1. very heavily sclerotized/

2. sclerotized, but only lightly so/

#40. The mesonotum <of the larva, sclerotization>/

1. sclerotized <at least to some extent>/

2. entirely membranous/

#41. The mesonotum <of the larva, degree of division>/

1. entire/

2. divided longitudinally into two sclerites/

3. divided into four sclerites/

4. divided into eight sclerites/

The numbers of sclerites recorded for divided mesonota are exclusive of the (lateral) pleurites, which can be seen in some of the illustrations.

#42. The metanotum <of the larva, sclerotization>/

1. sclerotized <at least to some extent>/

2. entirely membranous/

#43. The metanotum <of the larva, degree of division>/

1. entire/

2. divided longitudinally into two sclerites/

3. with two horizontally elongated slerites, the anterior one broad with an excised hind margin, the posterior one narrow and widened in the middle/

4. divided into four sclerites/

5. divided into six sclerites/

The numbers of sclerites recorded for divided metanota are exclusive of the (lateral) pleurites, which can be seen in some of the illustrations.

#44. The metanotum <of the larva, presence of brushes of bristles>/

1. bearing brushes of bristles/

2. without brushes of bristles/

#45. The metasternum <of the larva, bristles>/

1. with either a dense zone of stout bristles, or a transverse row of at least six/

2. with no more than a median pair of bristles/

#46. Abdominal segment 1 <of the larva, whether papillate>/

1. with <two or three> retractable papillae/

2. without retractable papillae/

In campodeoid larvae, which seldom construct portable cases, the body is dorsiventrally compressed, and the head is not or only slightly inclined; there is no lateral line, abdominal papillae are lacking, and tracheal gills are often absent.

In the eruciform type, which is associated mainly with portable cases, the body is cylindrical, and the head is markedly inclined; a lateral line is present; retractile papillae (usually one dorsal and two lateral), apparently concerned with maintaining the position of the larva in its case and permitting an even flow of water, are present on the first abdominal segment; and simple filamentous or branched tracheal gills are present on the abdominal segments.

#47. Abdominal segment 8 <of the larva, with or without a lateral comb of fine spicules>/

1. with a lateral comb of fine spicules/

2. without a lateral comb of fine spicules <with no more than a few spicules above the lateral fringe line>/

#48. The larva <fusion of terminal abdominal prolegs of the larva>/

1. with the terminal abdominal prolegs fused basally, forming an ostensible tenth segment/

2. with the terminal abdominal prolegs free of one another <i.e., not fused basally to form an ostensible tenth segment>/

Comments.

#49. <General comments:>/

British representation.

#50. <Number of species in Britain:>/

species/

#51. Genera:/


To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. British insects: the families of Caddis flies (Trichoptera). Version: 29th December 2011. http://delta-intkey.com’.

Contents