Margery J. Milne.
Immature North American Trichoptera.
Psyche 46(1):9-19, 1939.

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Immature Trichoptera
IMMATURE NORTH AMERICAN TRICHOPTERA
BY MARGERY J. MILNE
Randolph-Macon Woman's College,
Lynchburg, Va.
Several keys to the larvse and two to the pupae of North American Trichoptera are already available1 but none of them summarizes recent study of adequate material, and all but one are based either directly or indirectly on tables pre- sented by European workers.
A search for family and subfamily characters in North American caddis larvae and pupae has yielded the two keys below. Since the pupal stage is much less completely known than the larval, the key to the former is more artificial than that to the latter, especially with respect to members of the families Odontoceridse and Sericostomatidse. To somewhat offset this disadvantage, a very useful list of spur formulae is appended, summarizing the known information on this character.
11901.
Betten, C. in Bull. 47, N. Y. State Mus. pp. 563-564. A larval key compiled from European papers by Klapalek and Struck. 1915. Krafka, J. Jr. in Can. Ent. 46: 217-225. Original keys to larvae, guided by Ulmer's 1909 European work. 1921. Lloyd, J. T. in Bull. 21, Lloyd Lib. (Ent. Ser. 1) p. 15. A slightly modified translation of Ulmer's 1909 key, larvae only. 1921. Lutz, F. E. in Field Book of Insects (Putnam) pp. 58-60. A modification of Betten's 1901 key to larvae. 1925. Comstock, J. H. in Introduction to Entomology (Comstock) p. 560. A modification of Lloyd's 1921 key to larvae. 1926. Essig, E. 0. in Insects of Western North America (Macmillan) p. 175. A modification of the key to larvae in Lloyd 1921 and Comstock 1925.
1926. Sibley, C. K. in Bull. 27, Lloyd Lib. (Ent. Ser. 5). An appar-
ently original key to the pupae of species found on the Lloyd- Cornell Reservation, N. Y.
1933. Brues, C. T. & A. L. Melander in Bull. 73, Mus. Comp. Zool. Harvard, pp. 195-197. A modification of Krafka's 1915 key to larvae.
1934. Betten, C. in Bull. 292, N. Y. State Mus. pp. 117-123, the larval key a copy of Krafka's 1915 work, the pupal key from Ulmer's 1909 key.




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Psyche
[March
Caddis larvse inhabiting movable cases have the head bent downward so that the mandibles are ventral (hypognathous) in position, the long axis of the head at an obtuse or even a right angle with the long axis of the body. Those with a right-angled attachment are said to be cruciform larvae, those with an obtuse angle to be suberueifo~w,, Caseless larvae have the long axis of the head in line with the long axis of the body and the jaws hence at the anterior end of the animal (prognathous). Such larvae are said to be thysanuriforrn or campodeif o m
Case-bearing larvae frequently have fleshy tubercles on the sides and notum of the first abdominal segment. These are called spacing humps, and serve to keep a passage for respir- atory water between the larva and its case. Such larvae also often have a prominent projection from the prosternum, extending between the front corn. This is the prostem1 horn or prosternal spine.
The head capsule or epicraniurn splits at ecdysis into right and left halves. It bears the articulating surfaces for the mandibles antero-laterally and may or may not meet on the mid-line ventrally, anterior to the neck opening (occipital foramen). In some forma a submenturn or guh is well de- veloped, the gula being sometimes quadrate, at other times triangular or crescentic. It may keep the epicranial halves entirely apart, extending from the labium to the occipital foramen, or it may separate them only anteriorly, so that the foramen is entirely surrounded by epicraniurn. A U- or V-shaped emargination in the anterior margin of the epi- cranium on the mid-dorsal line accommodates the from to which the labrum is attached by a flexible membrane. There is no clypeus. The antennae are usually very small. Many larvae have a fringe of hairs along the abdominal lateral line, the so-called "lateral fringe," The abdomen fre- quently bears along the dorsal, lateral and ventral surfaces filamentous or branched structures called gills, although their respiratory function is doubtful. Around the anus filamentous or sac-like structures are often seen. These are the rectal gUla, which are seemingly retraetible into the rectum. Also apical on the abdomen are the p~olegs, fleshy structures with claws, used in locomotion. The thoracic appendages are true legs, and consist of five segments, a



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19391 Immature Trichoptera 11
large coxa articulating with the pleurite, a small trochanter (always indistinctly divided), a large femur, a tibia, and a one-segmented tarsus bearing a movable claw. Usually the tibia ends in a spur. In Leptoceridse and some Odontoceridaa, the middle and hind legs have the femora divided into two, the proximal half shorter than, or equalling the distal half. In the pup= imaginal structures such as antennse, maxil- lary and labial palpi, ocelli, tibia1 spurs, sternal ligulae and genitalia may be studied, in addition to the labral bristles, gills and anal processes of the pupal skin itself. All females have the maxiUwy palpi 5-segmented, but the males of some families show a reduction in this number. In some families in which both sexes have 5-segmented maxillary palpi, the terminal segment is secondarily annulated. Labial palpi are always 3-segmented. There are 3 ocelli present or none are found.
The fore tibise may have as many as 3 spurs, the middle and hind tibiae as many as 4 spurs. When no more than 2 spurs are present, they are terminal. A third or fourth spur is added part way up the tibia. The number of spurs is indicated by a spur formula. Thus 1-3-4 indicates that the fore tibia bears one (terminal) spur, the middle tibia a pair of 'terminal and a subapical spur (s), the hind tibia a pair of terminal and a pair of subapical spura. The
labra1 bristles are used to clean the gratings which allow entrance of water into the pupal case. The gills are much like those of the larva but often differ in number and ar- rangement. The anal processes are extensions of the pupal skin which cover the cerci and genitalia and often bear bris- tles for cleaning the grating which allows exit of water from the pupal case.
TO NORTH AMERICAN CADDIS LARVAE
1. Abdomen very much wider than thorax; very minute species
with all three thoracic segments heavily sclerotized above, living in portable silken cases which are much larger than the larvae : Hydroptilidse Abdomen not much wider than thorax; much larger. species, never with all three thoracic nota heavily sclerotized above in any case-bearing species, the cases when present not much larger than the larva? 2



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Psyche [March
Last abdominal segment never with a sclerotized shield above ; body campodeiform, the head held straight forward, forming a continuation of the long axis of the body ; abdomen of nine segments, the prolegs dis- tinct from one another; no tubercle on first abdom- inal segment; no prosternal horn; no lateral line fringe; abdomen depressed, the sutures between the segments deeply impressed ; gills usually absent ; rectal gill structures generally present but not always everted; larvae not constructing a movable case .............................................................................. 3 Last abdominal segment usually with a sclerotized shield above-if lacking it, the body cruciform (hypognathous) and the larva living in a movable case (Leptoceridae) ; gills usually present ............. .I0 Labrum soft, whitish, retractile under edge of frons 4 Labrum wholly sclerotized ............................................ 5 Mandible with a prominent tooth at middle of medial margin; frons with a deep asymmetric emargina- tion : .......... Philopotamidas, subfamily Chimarrhim? Mandible with no such prominent tooth; frons scarcely emarginate : .................................................................... ......... Philopotamidse, subfamily Philopotaminse Claws of legs long and slender, nearly straight, with only one basal spur; penultimate segment of maxil- lary palpus very long : .................................................. .............. Psychomyiidse,, subfamily Polycentropodinas Claws of legs short, stout, curved ; penultimate segment of maxillary palpi not especially long ...................... 6
Gills absent; only two bristles on convex side of man- dibles ............................................................................ 7 Gills present; numerous bristles on convex outer side ....
of mandibles ; all three thoracic nota sclerotized 8
Only prothorax sclerotized dorsally : .............................. ................... Psychomyiidse, subfamily Psychomyiirm All three thoracic nota sclerotized : .................................. .......................... Psychomyiidse, subfamily Ecnominse Gula an elongate, rectangular plate separating epi- cranial halves completely; all gill filaments in clus-



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19391 Immature Tricho pt era 13
ters arising from the ends of stalks, somewhat like the tentacles of Hydra ; large forms : .......................... .............. Hydropsychidse, subfamily arc to psych ins^ Gula triangular, never reaching hind margin of head, the epicranial halves contiguous for some distance ; gill filaments arising from the side as well as the end ......................................
of the stalk, more comb-like
9
9.
Dorsal surface of head flattened, forming a broad disc, enclosed by a strong carina which crosses the frons near its apex, setting off a small triangle; mandibles with broad, blunt teeth on whole inner margin, the interspaces broad and deep : ........................................ ........... Hy'dr~psy'chidse,~ subfamily Macronematinas Dorsal surface of the head flattened, but with no carina defining its limits; mandibles with sharp teeth api- cally : .... Hydropsychidq subfamily Hydropsychinas 10. Body campodeiform, the abdomen depressed ; larvae never constructing a movable case though sometimes building a fixed shelter ............................................. .ll Body eruciform or suberuciform, the head bent down- wards at an angle to the rest of the body; abdomen cylindrical, the sutures between the segments usually feebly impressed ; gills usually present; larvae always living in a movable, tubular shelter ....................... .I2 11.
Prolegs very well developed, entirely separate from each other; proleg claws long and slender, without teeth on convex surface; accessory claws sometimes present at sides of main proleg claws; maxillary lobes long and slender : ............................................... .................. Rhyacophilidse, subfamily Rhyacophilinz Prolegs short, the basal segments wholly sclerotized and fused to the ninth abdominal segment in a nearly vertical position ; proleg claws very short, with small teeth on the convex side; maxillary lobes short and broad; construction of a fixed shelter in late larval . .
life is usual : ................................................................. ............... Rhyacophilidse, subfamily Glossosomatinas 12. Prosternum with a horn or spine projecting down- wards between the front coxae ................................ 13



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14 Psyche [March
............................................... No such prosternal horn .I5
13. Body suberuciform; lateral gills on segments 2 to 7 usually pubescent with black hairs ; mesonotum gen- erally soft like metanotum, rarely with two small sclerotized plates ; abdominal constrictions well .................................................. marked : Phryganeidse
Body cruciform; lateral gills on segments 2 to 7 never pubescent with black hairs ; mesonotum generally entirely sclerotized, sometimes only with small plates, rarely completely soft ................................... .I4 14.
Mesonotum entirely sclerotized ; metanotum with three pairs of plates ; mesothoracic legs stouter and longer than hind legs : ...................................... Limnephilidse Mesonotum not entirely sclerotized ; metanotum usually entirely soft; middle legs not longer than hind legs : A few Sericostomatidse ( Goerinae & Lepidostomatinse) 15.
F,emora of middle and hind legs divided into a shorter basal and a longer apical piece; right mandibles without inner bristles ; no accessory bristles on back of mandibles : ............................................................. .I6 Femora not divided ....................................................... .I7 16.
Lateral line well developed ........................................... 17 Lateral line little developed or absent : ...... Leptoceridss 17.
Lateral line well developed, the 8th segment never with only sclerotized points representing the line ; labrum with a transverse row of many stout bristles before the middle, or if lacking these, then much longer than broad : ........................................... Odontoceridse Lateral line very faint, incomplete or absent, its place sometimes occupied on some segments by sclerotized points; labrum neither with a transverse row of ................................
bristles nor longer than broad
.I8
18. Antennae rudimentary ; pronotum sclerotized, meso- .......... notum never more than partially sclerotized : ............................................................ Sericostomatidse Antennae large, the basal segment broad, 2nd more slender and tipped with a fine bristle; pro- and meso- notum both sclerotized ............................................. .I9



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19391 Immature Trichoptera
19. Distal spurs of fore and middle tibiae not on promi- nences ; hind legs with normal claws; cases curved ........................................ tubes, never broad : Berseidas
Distal spurs of fore and middle tibiae on prominences; claws of hind legs abnormal ; cases of sand, broadly shield-shaped like a turtle shell, except those of very young larvae which have straight sand tubes, often ......................
with bits of mollusk shells :
Molannidse
1. Pupae very small (not more than 5 mm. long, usually less than 3.5 mm.), with very short thick antennse; maxillary palpi
5-segmented in both sexes; cases
mostly of silk only or of silk covered with very fine sand, the cases flat or thickest in the middle, usually attached at each end by circular discs of silk : ............ .................................................................. Hydroptilidse Pupae usually larger, the antennae nearly as long as the body, not especially thickened ; maxillary palpi some- times 3- or 4-segmented in the male; cases never as above ............................................................................ 2 2. Lacking both ocelli and a complete tubular case ........ 3 Either ocelli or a complete tubular case or both present ........................................................................................ 5 ........................................................................ 3. Gills absent : ................. Psychomyiidse., subfamily Psychomyiinse Gills present .................................................................... 4 4.
Spurs 3-4-4 ; anal processes large, blunt, not long ; cases made of pieces of leaves or small sand grains, the ventral side of silk only (in Phylocentropus the case is a long, branched tube of sand with only a turret projecting; in Neureclipsis the case is a trumpet- shaped net) ; .................................................................... ............ Psychomyiidse, subfamily Polycentropodinas Spurs 2-4-4 or fore tibiae with one or no spur; anal processes long and heavily sclerotized, with many bristles : .............................................. Hydropsychidas 5. Case complete, the pupa never in an inner silken cocoon ; gills often present ; anal processes often long,



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Psyche [March
rod-like and strongly sclerotized; legs with or with- ...................................................................... out claws 9
Case incomplete, the pupa in an inner silken cocoon; gills absent; no long or rod-like or strongly sclero- tized anal processes ; legs with good claws .............. 6 Inner silken cocoon spindle-shaped like a zeppelin or a fly. puparium, attached to the case only at its poster- ior end; case barn-shaped, usually of pebbles; 5th segment of maxillary palpi not annulated .............. 7 Inner silken cocoon either not complete or fused to case wall near its equator ; when incomplete, the anterior end lacking, the posterior end much as in Rhya- cophilinse; 5th segment of maxillary palpi long, curved and distinctly annulated ................................ 8 Spurs 2-4-4 : Rhyacophilidse,
subfamilies Glossosomatinse & Hydrobiosinse Spurs 3-4-4 : Rhyacophilid9~, subfamily Rhyucophilinas Spurs 2-4-4 : Philopotamidse, subfamily Philopotumirm Spurs 1-4-4 : Philoyota,m~idse, subfamily Chimarrhinse Ocelli present ................................................................. .I0 Ocelli absent ................................................................... .I2 Posterior margin of 1st abdominal tergite produced caudad in a distinct median process extending over base of 2nd segment; mandibles with a prominence from which the bristles arise; anal processes flat, somewhat rhombic, with 4 long bristles at the end; spurs 2-4-4 ; male maxillary palpi 4-segmented : ...... ........................................................... Phryganeeids Posterior margin of 1st abdominal tergite not produced caudad but with a saddle-shaped prominence, later- ally with short spines or with only two lateral tuber- cles set with numerous hairs or denticles; mandibles with no such prominence; never more than one pro- tibia1 spur ; male maxillary palpi 3-segmented ; anal processes long, more slender .................................. .I1 Labrum semicircular, anteriorly emarginate, the dorsal surface elevated, with a transverse furrow back of its mid line; spurs 1-1-1, 1-2-2, 1-2-3, 1-2-4, 1-3-3 or in most, 1-3-4 : ........................................ Lknephilidse



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19391 Immature Trichoptera 17
Labrum roughly rectangular, the anterior margin formed of 3 curves, in each of the two emarginations of which is a fine bristle; 5 longer bristles with curved tips vertically on either side of labrum ; spurs 1-2-4 (Pharula) or 1-3-4 (Neothremma) : .................. ......... Sericostomaiidse, subfamily Georinse in part Antennae very long, the outer part wound around the ......................................................... abdominal apex .13
Antennae scarcely longer than body, the ends never ......................................................... wound as above .I4
Two mesotibial spurs; mouthparts so placed that the pupal mandibles point upwards : ............ Leptoceridse Four mesotibial spurs; mouthparts normal or as ............................................ above : some Odontoceridas
Spurs 2-2-2 (Micrasema) or 2-3-2 or 2-3-3 (Brachy- centrus) ; labrum obtusely triangular to semicir- cular; maxillary palpi shorter than or but little longer than labial palpi, never stouter : .................... . . . . . . Sericostomtidse, subfamily Brachycentrinss ......................................................... Spurs not as above .I5
Case shaped like a snail shell, coiled in a flat spiral, made of sand grains of small size : ................................ ............. Sericostomatidas, subfamily Helicopsychinas ................................................. Case never of this form
.I6
Less than four mesotibial spurs ................................... .I7 Four mesotibial spurs ................................................... .I8 Body length not less than 5 mm. ; robust species: .......... ...... Sericostomatidse, subfamily Sericostomatinse Body length not over 4 mm. ; slender, small species : .... .......................................................................... Berseidse Less than 4 metatibial spurs : ........ some Odontoceridas Four metatibial spurs, the formula 2-4-4 ................... .I9 Anal processes lobate : ...................................................... ....... Sericostomatidse, subfamily ~e~idostornat~nse Anal processes rod-like ................................................. .20 Case of sand, flattened dorso-ventrally and with lateral flanges, closed by discs of silk at the ends, that at the posterior end having a vertical slit, that at the ante- rior end a horizontal slit : .......................... Molannidse



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18 Psyche [March
Case not as above, and differently closed ................. ..21 21.
Case of stones with ballast rocks at the side, straight, never curved : .................................................................. . . . . . . . . . . . Sericostornatidas, subfamily Goerh in part ................
Not as above ; case with a definite curvature : ........................................................ some Odontoceridse In families Hydropsychidse (with subfamilies Hydro- psychinse, Arctopsychinse and Macronematinse) , Psycho- myiidse (with subfamilies Psychomyiinse, Polycentropodinse and Ecnominse) and Philopotamidse (with subfamilies Philopotaminse and Chimarrhinse), the 5th segment of the maxillary palpi is secondarily segmented in the pupa and adult.
In Leptoceridse it is long and slender and often curved but never segmented. In males of Phryganeidse, the fifth segment is lacking, so that the maxillary palpi are 4-segmented ; in males of Limnephilidse
(with subfamilies
Apataniinse and Limnephilinse) and Sericostomatidse (with subfamilies Brachycentrinse, Helicopsychinse, Lepidosto- matinse, Goerinse and Sericostomatinse) the 4th and 5th seg- ments are lacking so that the palpi are 3-segmented. The females of these families and both sexes of families Hydrop- tilidse, Rhyacophilidse (with subfamilies Rhyacophilinse, Hydrobiosinse, Glossosomatinse) , Berseidse, Molannidse and Odontoceridse (with subfamilies Odontocerinse and Cala- moceratinse) have five segments to the maxillary palpi. In all Limnephilidse, Philopotamidse, Phryganeidse, Rhyaco- philidse, two genera of Sericostomatidse (Thremma and Neo- thremma of Goerinse), and in six genera of Hydroptilidse (Agraylea, Allotrichia, Ithytrichia, Neotrichia, Oxyethira, and Polytrichia) there are ocelli, but elsewhere they are lacking.
Formula Family Genera Concerned
0-2-2 Lepto~e~idse Leptocella, Leptocerus, Setodina, Yrnymia
0-2-3 Hydroptilidse Neotrichia
0-2-4 Hydroptilidse Hydroptila
0-3-4 Hydroptilidse Agraylea, Allotrichia, Ithytrichia, Ortho- trichia and Polytrichia




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19391 Immature Trichoptera
Hydropsychidse
Rhyacophilidse
Limnephilidse
Leptoceridse
Limnephilidse
Limnephilidse
Limnephilidse
Limnephilidse
Limnephilidse
Sericostomatidse
Hydropsychidse
Philopotamidse
Sericostomatidse
Leptoceridse
Sericostomatidse
Berseidse
Sericostomatidse
Sericostomatidse
Sericostomatidse
Odontoceridse
Odontoceridas
Hydropsychidse
Molannidse
Odontoceridse
Philopotamidse
Phryganeidse
Psychomyiidse
Rhyacophilidse
Sericostomatidse
Psychomyiidse
Rhyacophilidse
Genera Concerned
sometimes Hydropsyche
Protoptila
Glyphopsyche (areolatus)
CEcetis, Triaenodes, Ylodes
Apatidea (nigra) , Chilostigma, Glypho-
psyche (bellus, canadensis, irroratus,
pritus) , Homophylax (nevadensis) ,
Ironoquia, Neophylax ( fuscus), Steno-
phylax (subfasciatus), Zaporota
Anabolina (litha, assimilis), Neophylax
(ornatus)
Anisogamus (antennatus) , Apatidea (all
but nigra), Ecclisornyia (all but simu-
lata)
Acronopsyche, Drusinus, Glyphopsyche
(ullus) , Halesochila, Oligophlebodes,
Platycentropus, Stenophylax (circu-
laris, dan, guttifer )
all genera and species not indicated above Neothremma
sometimes Hydropsyche
Chimarrhinse
Pharula
Athripsodes, Mystacides
Mierasema
all
Helicopsyche, Sericostomatinse
some Brachycentrus
some Brachycentrus
some Marilia, some Heteroplectron
some Ganonema, some Notiomyia
Arctopsychinas, Hydropsychinse except
some Hydropsyche
all
some Ganonema, some Notiomyia, some
Marilia, some Heteroplectron, all
Namamyia, all Nerophilus
Philopotaminas
all
Psychomyiinse
Glossosomatinas, Hydrobiosinse
Goera, Pseudogoera, Lepidostomatinse
Polycentropodinse
Rhyacophilinas




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