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The scientific publications of the United States National Museum consist of two series—the Proceedings and the Bulletins.

The scientific publications of the United States National Museum intended primarily as a medium for the publication of original, and usually brief, papers based on the collections of the National Museum, presenting newly acquired facts in zoology, geology, and anthropol- ogy, including descriptions of new forms of animals, and revisions of limited groups. One or two volumes are issued annually and dis- tributed to libraries and scientific organizations. A limited number of copies of each paper, in pamphlet form, is distributed to specialists and others interested in the different subjects as soon as printed. The date of publication is printed on each paper, and these dates are also recorded in the tables of contents of the volumes.

The Bulletins, the first of which was issued in 1875, consist of a series of separate publications comprising chiefly monographs of large zoological groups and other general systematic treatises (occa- sionally in several volumes), faunal work, reports of expeditions, and catalogues of type-specimens, special collections, etc. The majority of the volumes are octavos, but a quarto size has been adopted in a few instances in which large plates were regarded as indispensible.

Since 1902 a series of octavo volumes containing papers relating to the botanical collections of the Museum, and known as the Con- tributions from the National Herbarium, has been published as bulletins.

The present work forms No. 85 of the Bulletin series.

RIcHARD RATNBUN, Assistant Secretary, Smithsonian Institution, In charge of the United States National Museum.

Wasuineton, D.C., April 30, 1914. 1

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Genus Paurocephala

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Genus Heteropsylla. texana.

AMO RACRTD 2 oe coe ae ee ie asco etcetera fOrelpatocs oOo 2 Rae ee a aera en eee RR se ae eee CUB TN ee cts ie ee ere pe Pn a Eo ete

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PLO ZOTNUAA </. 28 oc are pa er ee ea cee ine claripennite: 2: 262.0 ee a0 Se Ieee cie as eect cn cian x NIT ah 0/2) 01 11 ep ga ned ea cli a Perea EY 248 hs drt arad se

Subfamily Carsidarine. .

Genus Preysuila. 03. (2052.26.05 cee a seis ae age ree eee eerie Cnwesii. 2 ce ss Sear ee ea ee QUMSG ei pe ce eee ace era StS he els a Se de


CE (ey og) Te 0) oer 1 rao Wee TO RAM RC le ee IR ESS os ake ye aie COTMICUIS are ee eee er Taye ot ey Sena aera Pears)

Gems @arsicarary tock eer eclectic as aU peer per ara ea BIgaTIbeAs. ice a septa i alee ara MRE oreo cee

USSR LO. sigs es Soe ee ag doe

TLS KAGAN A she le, Sea chee ear ee a eat pagearsbge ec ee hee

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fonts Rbimopsylla. - 2oisc.2 ooo scierta ee ee are ae ie Cee ere el etay reiet BOLE Z UR. cae pee a0 Aan ace eae is eer rs Us Lira ase

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ANTeENNAtTAE We oe ees So eet eS oe aah er eae eh erat at state erate

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Geniiis Kuwayama so. 5003 scck Selstrs hee See Sats os es Se ei a sHeGiCAgIMIs 1. eek eee see Sikid od Dot Loe ORE Cee Cite rte OBRACEMBIS! 2 oe 22 35) 2S ORAS SR Se ate ee an ie eae cae


Genus Tewxronota ssc Pec ee Ae RE SN Ie ak Ie esa ES A TOACULA TA eee eS Ne Oe ain at thee ROO ee Cees aE ACUTPS MAAS! |e S24 Ay Ue tn area eee cece eer longipenmis.:). 55.2 bey see Oa ee ie Cee ee ie oe ects GENUS HPATALTIOZO 2c cele ile crac hehe aie wk RE ara eet (EM ena eng NaN waar COCK ere lla seals i io EN ORO ae ea Or ee ne Se a ea ALDOLEMSIS eek a a Ae EUR cats at ee nea Ue MACUMBE NTIS. 35.5. o's Stok tic oe menaiets cere aia tet etek eerie


Subfamily Triozine—Continued. Page. ACUTE NOTA ee errata tc ne ste ieee cence star reg ace etn afer fs par 74 (IS) Lge A alte elt a ER RLS Spe RADU BEE PDN 9 VE ROE Es RAISES 77 irew I AipaTils sre so rs kee he et a ecm cheek te ceric nin, 78

MAIER sages o aaa send eeweo er tae as aerial aoe = 78

WME aia, OP ones ne ne oe so eat ee Be Es aeeints 80

MAREE ero Sess ee Sek ee peta: ee ER IE ae She 80

RIMINI eo on Sa ee See ie mae ee ir 81

CAAT ee oe a = ok oa na fs Cee ee es = ee eee 81

lGnPInpylue 2-22-2222 oes sce + ae ee an on che 82 GisdeIPUNC tA. s.~.. 252s semen ee ae ne alae 82

PU ete eke ic Sot as os Bee a Reem = aoe oe cia 83

ATOR CADIS ore ree ise cia Oe See aL eres eee 84

LG AE a a tee ease ahead a ee ce an eae ae 85 OPUS eS weary taper aarea eae Beare ae eles eyte ress 85

ROD Eco oe en ce Meri a ties Soe reie ne ee See he e eihet 86

tripunctata. 0552222. 2 2 S25 eee h nar eke poe oe 87

PIB foo Pe ce ee oe ee en ee ORR cemeteries 88

MILER ee Ek Boe 5 ie NR Hee ta Dae area Eat ean 89

BANNAN ese es tae ho aa Fe ne Ae NORE S 3 mealies 91

BRED TLS 5 sche re pe as ay = ae Ee 91

AG MpACORUIG: 20 oad = oda tees orem aan oe me i ain 92 nicaraguensis...........------------- 2222-2 e ee eee eee 92 etyliietacc..-.<- +2222 --- ee a are eran eae ae toe So 93

HylinNeRbene a. 2245 - ge pee a en as aaa th aaa Sinn 93

SREP ean es oe a eto tc hatin ae eeieiecs eae sata 94

PMPATA I oe cect te en Sm et eat ks re ape a 95

MAPTON es aes oS Se sce oan ae en wa ae De Poe 96

Seat ee es ese ke os RR ore oa ae 2 97

Se MOPPIOUPEe. foo oa ean Oa eee eee Saas Ao cige t wemeenG Se 6 Sook 97 PAOROGEMIN Sees Scere oo Ot Ce eee ee cece he mae oe @ 98

Bieta IO OUN 3h eres A oo ora ain oe Se eeiaes te Saale ns = 98 TIAC Uist 90S oe eke eae as eye oe cee eee 98 BCulptoconUs: 2.221 .2254 == 2422-325 <b een hee = =e 99

AaGaeb Ys 251568 oe ne as tna = ete etek = oes - 100

Genus Ceropsylla.........-.------------- 22-222 eee eee eee terete rece eee 100 Rideranylns fs 2 265 2220. Ss oe e's le m= - 101

SALW ate eno oe ap mats Sk 8 aes eect lara Ae 102

johnsonil. 2/22... .-.- 2+ 222-222 oes eee een neste e sees 103 SrePnPETERITIIOS ae foe ore 2 os 32 2 oe ds po oe eee ne emee nea ta a Pia 104 BOT ee ates te cas Sono a5 TI RO eg eee te Seen S55 104

Subfamily Psyllinz............---------------- 2-2-2 2e eee erect eee e eee 105 Tribe Pachypsyllini.............---------------- SOs ee ere ota Satch 106 Pennaihlerta sere oe 225 fo oes doe eae ee ene Pena ee Sais 106 With eee iese 2s eyes Pe eke REDS, eet <n ere 107

Genus Tetragonocephala.........-------------------+--+-+rere reese 107 fag 5 se a noe air Ste Si oa AROS aaa) 2 = 108

Genus Pachypsylla........-.------------+- +--+ 222 22s eee rere eee 108 VESTAS GD sas etna Stor Neon ie VST eee a 3 Cin ainie' ats) s= 109

Ore MR See oS eee eater is ea GE ee ws Breet 110

Aopen CMLHY 65 onsd 2s Saar asta = i eegee 5 ey RA ee So = 112

OC rpemima 2s. 425 2 yg eee ae eh ee oie | 112

LULL oo re Seen ro me es oo heat 113

quis. 350 3.0.2 o ee es <a Roading 2242 =< - = 113


Subfamily Psyllinsee—Continued. Page. Tribe Muphy urn Jac... 0 ie re eet eee ce ec 114 Genus Katacephala..-...2.-- 2202 2 one see = ee eee cee ee 114 PTATICICOD es. <)- <iere im) Fe eee epee ie eee cn oe 114 SACU LSS =n a oe = = 5 wie Sine ise rater ae eevee ate te ee Reeectte ant 2 RE 115

Genta Mupbytirs®: 25. 52% pee ace pines eee re ee aia tence 115 QTCTOSTA DN YL. wis. o aya 2 aera ate oi ot a bee 116

MEW CTPOMIIS 5 fice al ieee siete le oi eae ulelch cs 117

SPDUbb. cane odie she ks ait che oe lee eae a oer NSS 117 APHUICOlA 502 22 sc dic sieht ees eee el ae me erence on 118

Mra be Avy tain «1. 2's <b: 2m = Se eeepc = eee ee eee aioe re 118 Genus Huphalerus. ojo . sk poo as cele ee tee creer ne 118 MUVOTOR 5 ovina xo, clk 2 ans eae een © er A ree 119 FUPIPOHINS <6) a/c uA sacle re ace ee Sa rae esse = 120 RTRRNTUEC ULL URLS eS orien ance ee te eater al 121 WETMLCUIOSUS A 2) oct ate Seta che Le ne ete ae a 121 POFOPIRQUIUIS Sai nfs Pia asere = So 2) Se ieee Sa or ator a 122

Genus "Aryiaina. 2c so .2 5 es sb oae se occ ccleaner es 122 TOWUSDS yee ce 22 irae ees aca san at nee ee sooo fe 123 FUSCIPENDIR: 6 =. 23 x ie oi tht els faci eet 125

PONMISTO HE. Cae). Fs Riek Siele SEA Rin loins ae ees etre 125 TUDOSIEG ici be 2k be caeeyals 2 Sco 6 Sie eae en etary caterer 126 BSSIMOT A. ss ei ods ei sive DAR rele tae ae Sea et 127

CTU Te ree 128 Ghelifera. (5 i. 6 PRs ciate sede dS calc Ra pea ee ee 128

BUNOKP OS! <b cies nS weet pe eta ee Ge ei re ae ee 129 Ceanothiee: ..o./52 525 4../2 3 5 2 fin ante nop Wee oie a OO 130 BOULERt AN. = 665; Sc. 4 oe oh Salar ic RIN ote an Giles area ee cde ae 131 PUbEsCONB et. Do lla an ate se Urea es ire eel en ate cre 131

Genus PsyMopsiss. i. a2 222 Sebi eve mises cin eae ete eae 132 FPAXIMICOMA eos cis nes eae SSS oS ale ni as te Reta Se aN ES oyavens ie 132 TMORICAM AY Sie isl 2 ee an ee eta NC a ee a 133 Tribes yee eho ahr tal ORES A AOS atte Cae A ah 134 Gemma Matava 9 ooo sie sas arn hat Speier ee aa ec eR 134 PENDS HET OB TaN aia cies. asst eles ope a eRNRE hea ea L Aa Paeae eia 134

CUBR Sa on Ce sie EEE se NSS ee eae 135

Genus Paylla i. rcs Sort c's wins cheetah eiencys eamicla te eno aes ea eee 135 SRNODE Ba ok ao ts =n kee ea en ce ee Sl eo 140

BUM toes cts Va iat ee Le os cs Us aie lee alah 140 parallel ee oj.) Use eles tae ieee tsa ets on a es 141 INACUIATA es o> be Satna es CNS tie es ce oe oe een eer eee 141

PTE VAR bee tek sie ra ie Ree Be ue ieee in, be 141

MUN Ute hese: S63 35 SSe aee Sees De eae ita eee 142

COBY es eer bos a Seni ee tock, cag coin le yan cn 2 ae a 143

UNDE oie so tis, 2) a lars Se ceatelune cham ehatelcl cic e le 3a uaa enna 143 yeaa sec sti cSt ewe <=. stodeseienteere ds eect. 144

SURG OULD eee as Shinde eae 2 ee ee ee 146 BOMCTICANA: oo a ees pase sale eee net ese ER Ee ee BBE 147

BYEUTA OE soci nic lichen sak ose eheu Poe pe Ie wai Mapes eke NN cr ac aa 147

PLN a oh eis iaphG AS eco 2 Se EN oe OS a dane 148

BUDS oc oie ctege ors sent toch ce leer tS oe op era 148

CUA TANT OB BA ys cct cate arenes hee in nec nm RRMA ES ON a 148 Alaskensigecs sc oposite eRe 149


Subfamily Psylline—Continued. Page. Tribe Psyllini—Continued. Genus Psylla—Continued.

Buiter sue ek Sch ee A icls A means ae an RE eS 150 amp nacilas x98) SES 58.2 RRS. RGD NES. a 151

COR MSTCR ME eh bic yigiaws A | amb, male Mie ons 8 BEL Ss nk 151 SRR etc fn tn 2a "2 eS ee Bre Ree ein Sy 152 PUTT revert cine nee Con a es CR aa eINY Oe Pee 152

BVO Win ciety. 93) et eis poe crue iY NE Ieee 153 POTN) 02 ren Se ee ne epee Be re rR) =o cs a4) eRe ee ye 154

BUS Ura wears ee eeiste)s wis Sy ein pe, oe See ape ane = lead RP 154

j LOE I I Oe en RMR Tes PINS. TNS ee ees SE 154 SALINE ao oee Rae Oe ats CMe Share 2 ae eee ec ee 155

spar Tisnes gC Shar oes opto oo Pye tO Cae eas ob 8 a 155 GeleR soe seca ones ae cs ee eee ne ae ei eee © ener ene eee 156 Rint americand... sess Ltt eee eee ee Se nee 156

Cal ates oO ee. oti: SWANS Beh eRe fe pana cael ak ae a de 157 PULCRPOPNNG : a. etek ot hs epee ee Ries eee te ieee 157 Pa eat A ie ae ee ee se acu oN 158 PEUZEDONEIS Ds ces ele e a ee | as eee Ree net ue IBY SO nee cee 159 MNGUMEGUE cc! Concer et Seat kee Ue Rec ee Ee ae ee 159 recticepe provatichers #20! JEyl22). AVR Ae. 2b Se 159 ire pilin quadricQmnis tsi) Yooh 28. asa Se it alee 160 BADIM OR 53 ota ert e : bold. Rise eine ER Mest toes age 160 Psylla duvaue...--.- Sate ae aia) S a can ofan A A ci 160 (ELT SLES a NAN 20g a ES Rn ge ne AT 161 SEERA TREATS so sa ep Non ee toe ee woe Soe ARS Baa wee SaIeL Ss 171

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By Davin L. Crawrorp,! Of the Laboratory of General Biology, Cornell University, Ithaca, New York.


The family Psyllide, or the Jumping Plant-lice, have received com- paratively little attention in the New World, especially from the systematic point of view. A relatively small number of species have been described, but no serious attempt has been made to relate the several genera represented by these species.

The European forms have received a great deal of attention, notably by Dr. Franz Loew and now by Dr. Karel Sule. Others have made some contributions, but in a much more unrelated manner. With the two names just mentioned, the name of Witlaczil should not be omitted. Some very good work on the internal anatomy has been done by him.

Until 1848 only a few genera were recognized, most of the species being placed in Psylla. At that date Foerster divided Psylla into several smaller genera, most of which are still valid. In 1878 Loew published his Zur Systematik der Psylloden, in which he established several additional new genera and tabulated four subfamilies— Triozine, Psylline, Aphalarine, and Liviine. With the exception of the latter, these were separated from each other on the basis of wing venation characters.

In his subsequent work he followed this same system of classifica- tion and there soon appeared more subfamilies and many more genera. Other workers during and since his time have employed his system of classification, also. The basic diagnostic characters used by Loew in this system were largely venational. The presence or absence of the cubital petiole (M+Cu), and the relative length of this petiole, when present, and the radial stem (or discoidal subcosta), were the two principal characters for the separation of subfamilies.

In undertaking systematic work on a large collection of Psyllide some four years ago, Loew’s system of classification was employed because it was practically the only one to be used. The collections before me were very large and contained very large series of speci- mens of many species, in which there would naturally be more or

1 Contribution from the Entomological Department of Cornell University, Ithaca, New York. This su- persedes the former papers by the author on this group. i


less variation. It was soon found that by Loew’s system very closely related species were thrown into different genera and even different subfamilies. Sometimes, too, specimens of the same species were separated into different subfamilies. This was true especially of several species of Aphalara and of related genera.

As the work progressed and other large collections were studied, many unsatisfactory features were found in this system and a great many difficulties encountered. Some of these have been mentioned in more or less detail in my former papers on this group. It became apparent that any classification based principally on wing venational characters would be artificial and unsatisfactory.. At the same time other characters were noted that seemed to be more fundamental and whose use in classification seemed to place together certain obviously related genera.

The form of the head, for instance, was found to be very significant in diagnosis. In some genera the frons is a visible sclerite between the gens, while in others it is completely covered by the genz which in the latter case are nearly always produced into conical processes. Genera related or separated on this character were found to be distinctly related or separated in other structural characters, as well.

The form of the vertex, and that of the pleurites of the prothorax and of the pronotum, the armature of the hind tibiew, and several other structural characters, have been found to correspond closely in certain groups of genera. These, naturally, do not divide the genera into sharply defined groups, but the groupings are, at least, more sharply defined and less artificial than by Loew’s system.

As a result of this study, a complete rearrangement of the genera of Psyllide is herein presented. While only the American genera are treated in this monograph, yet most of the genera of the world have been considered in connection with this new system of classifi- cation, and it appears that this system will be very satisfactory for all.

The American genera have been arranged in six subfamilies— Liviine, Pauropsylline, Carsidarine, Ceriacremine, Triozine, and Psylline. Some of these are new names and those which have already been used are here used with different limits, representing a different group of genera. Each is described and discussed under its own subhead and need not be discussed here. It should be noted, however, that the old subfamily Aphalarine is not recognized. Its typical genus, Aphalara, has been transferred to the group Liviine, and the other genera formerly placed in it have been referred to Psylline or some other subfamily.

Some confusion has arisen in the past over differences in the nomenclature of the external sclerites, and these differences have been due largely to our imperfect knowledge of the homologies of


these external parts. In the following pages a brief discussion of the homologies of the sclerites is given, with an explanation of the terms used in the systematic portion of this work.


Anatomical studies on the family Psyllide are not numerous, but in proportion to the systematic work on the group they are quite extensive. All of this work has, however, been based on a relatively small number of species and therefore the results are not entirely accurate.

The most extensive of these works was by Emmanuel Witlaczil in 1885, Die Anatomie der Psylliden. The largest and most impor- tant part of this paper is on the internal anatomy, with a relatively small part on the external morphology. He discusses in more or less detail the following subjects: Segmentation of the body wall, musculature, wax glands, tracheal system, nervous system, digestive canal, circulatory system, reproductive organs, and finally the relationships of the family to the other groups of Homoptera, both the Phytophthires and the higher groups.

Loew (’76:187-194) discusses very briefly the external anatomy, but in a very general way. H.B.Stough (’10:121-165) has more recently studied the morphology of the hackberry psyllid, Pachypsylla c.-mamma Riley. This latter work is not altogether satisfactory from the point of view of clarity and definiteness, and also shows several errors in the interpretation of sclerites. It may be stated, however, that the species of Pachypsylla are among the most difficult for the purpose in view—of homologizing sclerites of Psyllide with those of other Homoptera—and this may account for the errors.

Some very good work has been done by Miss Patch (’09:117-121) on the wing veins of Psyllide, homologizing them with the veins of Aphidide, Coccide, and Aleyrodide. The Comstock-Needham system of nomenclature of veins as applied to many other groups of insects has been applied here by Miss Patch. Because of its sim- plicity and superiority in all ways the same nomenclature is followed in the taxonomic work of the present paper.

No attempt has been made by the writer to go into the internal anatomy of the Psyllide; nor is the external morphology presented in as much detail and completeness as would be desirable if the scope of the present work were not so limited. There are many very curious and remarkable developments in the members of this family, and several sclerites which are difficult to homologize satisfactorily with other Homoptera. These must be studied more carefully before the conclusions can be relied upon with absolute certainty. Certain phases, therefore, of the external morphology are presented in somewhat of a tentative manner.


The present study has been based on a large number of species, representing many genera of the family, as follows: Inia vernalis and L. coloradensis, Aphalara veaziei, Pauropsylla sp. (a Javanese species), Paurocephala magnifrons, Apsylla cistellata (Indian), Pha- copteron lentiginosum (Indian), Heteropsylla texana, Euphyllura arbuti, Arytaina robusta, Psyllopsis fraxinicola, Psylla alni americana, Psylla pyricola, Trioza diospyri and T. albifrons, Paratrioza arbolensis, and many others compared but studied less carefully.

Apsylla cistellata, an Indian species, is somewhat generalized and proved to be very valuable for indicating the path of specialization in the more highly specialized forms, or those considered to be more typical of the family. It was pointed out in the description of this species (Crawford ’12¢:421, 429) that it was scarcely psylline in many respects, and in fact the generic name, Apsylla, was suggested by that fact. Many developments so complicated and so highly special- ized in Psylla that it is extremely difficult to understand them become much clearer when the Indian species is compared with them.

The methods of study used have been both gross dissections and microtome serial sections in balsam. The dissections were made in a liquid—alcohol, cedar oil, or glycerine being the best, and for most purposes alcohol the best—and under a binocular microscope with a magnification of about sixty diameters. The specimens were first softened, cleared and distended in a warm, strong solution of caustic potash and then placed in a watch glass on the microscope stage with a strong tungsten light directly beneath the stage. In this way the sclerites of the exo-skeleton become easily visible because of the semitransparent and distended condition of the body wall. By means of fine needles and special tweezer-like scissors the insect may be very easily dissected.

Another method of dissection which proved to be very valuable and which is offered as a suggestion to others for similar work is as follows: Soak the specimens in warm caustic potash for ten or twelve hours, then place in water for a few minutes, and dehydrate with alcohol; then soak in cedar oil for several hours and imbed in par- affine. With a microtome, section away one-half of the insect, either longitudinally or sagitally, dissolve away the parafline from the remaining unsectioned half with xylol, and mount in balsam with the cut surface up. No staining is necessary unless a chitin stain is used in cases where the body wall is mostly depigmented and transparent. A half insect mounted with the open side up shows with remarkable clarity and perspective the internal skeleton and the internal side of the sutures. This method was found to be valuable also for the study of the musculature, but of course for this the specimen must be first fixed alive instead of soaking it in caustic potash.


As a third and very essential method of study serial sections of specimens fixed in various fluids were used. Transverse, sagital, and longitudinal sections were made.

HEAD. Figs. 1, 3, 5, 15, 17, 21.

The head of the members of Psyllide in the essential parts is not materially different from that of other Homoptera. In appearance it is very variable within the family because of the peculiar pro- longations of the gene or the vertex or some other part of the head.

The vertex is a large dorsal sclerite comprising usually most or all of the top of the head and divided by a median suture which is always easily visible (fig. 5). At the extreme posterior angles of the vertex are the two posterior ocelli. The surface of the vertex is variable, being sometimes flat, or more often with irregular depres- sions or fovex, or sometimes rounded forward and downward. Its shape also is variable from quadrate to triangular or semicircular, or each of the two lobes may be rhomboidal.

The frons has in most cases been overlooked in the Psyllide and the clypeus erroneously called the frons. In Psylla, Trioza, and many other genera the frons is searcely visible as a sclerite, but in some species it is very prominent, as, for instance, in Paurocephala magnifrons (fig. 16) and Invia, Aphalara, and several other genera. In all cases it is present as a small or large sclerite bearing the anterior ocellus at its base or the end nearest the vertex. In many species of Psylla the ocellus is imbedded between the vertex and the gene and no fronsis at first apparent. After careful examination, however, the small sclerite of the frons becomes visible below the ocellus and between and beneath the genal cones (figs. 15, 21).

The shape and form of the frons is very variable. In Paurocephala magnifrons, a Mexican species (fig. 16), it is a relatively large, con- spicuous, pentagonal sclerite occupying an anterior position on the head (actual, not relative), with the vertex articulating on the two sides, the genz on two sides and the clypeus on the fifth side or apex. The anterior ocellus is at the base, the same relative position as in all the other species. The sutures and sclerites are almost dia- grammatically clear in this species.

In Invia (fig. 20) Rhinocola, Aphalara (fig. 18), Aphalaroida, Paurocephala (fig. 16), Pauropsylla, Heteropsylla, some species of Carsidarine, and others the frons is very distinct but occupies an inferior position on the head and is more elongate and the sutures sometimes less distinct than in the Mexican species mentioned above. In these forms, too, the anterior ocellus is borne at the base of the frons (the apex of the head), and the frons appears sometimes as the stalk of the ocellus. As stated above, the frons in Psylla and many other


genera has been suppressed and becomes almost invisible in some cases. In Pachypsylla it is so small and indistinct that Mr. Stough overlooked it as a sclerite and called it the “‘ligamentary process attaching the frons (really the clypeus) * to the head.” Figure 15 is from a sagital section through the front ocellus and the frons. The suture between the vertex and the frons is very distinct just above the ocellus. The frons is seen to extend downward beneath the genal cones which lie over it and to attach to the clypeus a little farther down (fig. 15).

A complete and very interesting series may be found within the family, showing the suppression of the frons from a large and promi- nent sclerite to a very small one which is little larger than the ocellus attached to it. The variation of the frons in many other groups of the Homoptera is very similar, and there is little doubt but that a comparative study of this sclerite throughout the whole suborder would throw much light on the taxonomy of the group and the rela- tions of the families within the group.

The gene are very large and comprise the largest part of the head ventrad.2 In Livia (fig. 20) the gene are two sclerites, lymg one on each side of the elongate frons and between the vertex in front and the clypeus behind. In all cases the antenne are attached on the edge of the gene near the vertex. The variation in the form and shape of the head is due mostly to the variability in the form of the gene. From the simple condition as mentioned above for Livia there is a gradual pushing outward of the genz to form two spherical lobes or two conical processes projecting downward or forward. These processes have had various interpretations, and various names have been assigned to them. Some writers have called them frontal cones, or frontal lobes, or frontal processes; Slingerland called them ‘““cones of the clypeus’’; Loew and other European writers have called them stirnkeln, and cont frontales. The writer in previous papers has called them facial cones, a noncommittal term. Stough is inconsistent in recognizing the sclerites from which these cones arise as the genz and yet calling these processes frontal cones, and at the same time calling the clypeus the frons, a sclerite which has no relation to the cones whatever. The term genal cones is applied to these processes in the taxonomic work of the present paper, and, of course, this is the only possible interpretation of them.

Usually the genz are inferior in position, but in some species of Carsidarine, notably in Carsidara (figs. 150, 151) a part of the top surface of the head—what appears to be the vertex—is formed by the gene. The vertex consists of a pair of narrow oblique lobes

1 The parenthesis is my insertion. 2 In all of this discussion the position of the sclerites is described as actually found in the Psyllid head, and not as in the typical or generalized insect.


with the front ocellus far from the front margin of the head, and the gene forming the front part of the head with the antenne attached on their front margin. In Huphyllura, also, a part of the top of the head is formed by the gene (figs. 34, 36).

Behind the eyes is another sclerite, the occiput, which is often not easily distinguished from the gene, although the suture between it and the vertex above is always distinct. In Livia this is very large and extensive (figs. 3, 20), and the sutures are distinct. In most of the genera, however, it is less extensive and more closely fused with the gene. The occipital foramen is surrounded by this sclerite.

The elypeus is a relatively large sclerite and very prominent. It is usually pyriform or cordate in shape, but sometimes more or less conical (Aphalara calthae, Paurocephala ilicis, and Ceropsylla john- sonii). The large end usually overlaps on the frons and often covers a large part of the latter, as in Psylla, Trioza, and many other genera. It is often obscured from view from in front by the genal cones which project downward in front of it. The other end converges rapidly toward the labrum and labium (fig. 15). The suture between the clypeus and labrum is quite distinct (im a good preparation), dividing off a relatively small and short labrum. Stough (710: pl. 29, fig. 1) has indicated an extra suture in the clypeus, and thus the proper number of sclerites is obtained after omitting the frons and calling it the ligamentary process. The epipharynx is a very small and inconspicuous sclerite.

Appendages of the head.—The labium in the Psyllide is very peculiar in being sharply flexed at a point between the forecoxe and the distal portion extending perpendicularly downward. This distal portion only is movable, the basal part being held rigidly between the fore- cox. The basal segment is thin, being membranous in appearance but really well chitinized. It is more or less internal, being covered partially by the prosternum. At the beginning of the second seg- ment, or at the tip of the first, the labium makes a sharp turn and passes downward. If the head were in the normal position of a generalized insect, this sharp turn would be perpendicularly upward. The furce from the prosternum are large and heavily chitinized. The second labial segment passes down directly in front of this and is apparently supported and strengthened by it. In some species, Psylla alni americana for instance (fig. 15) it seems to be partially surrounded by the furce. The labium passes out between the legs of the furce and immediately behind the forecoxe, thus appearing to arise from the prosternum instead of the head. The distal portion of the second segment and all of the third is outside and forms the visible beak or rostrum. ‘The latter is movable and may be exserted and drawn in more or less, being movable on, or within, the profurce.

6060°—Bull. 85—14——2


The mandibular and maxillary sete are attached near the base of the clypeus and pass out along the labium. They are very long, often very much longer than the labium.

The eyes are large and usually more or less hemispherical, project- ing laterad from the side of the head. The facets are relatively very large. In Livia (fig. 20) the eyes