G. W. Wharton.
Four New Peruvian Chiggers (Acarina-Trombiculidae).
Psyche 55:87-100, 1948.

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FOUR NEW PERUVIAN CHIGGERS
(ACAEINA-TROMBICULIDB)
BY G. W. WHARTON
Department of Zoology, Duke University
The specimens on which this paper is based were col- lected by 0. P. Pearson and were obtained through Charles Reniington from Harvard's Museum of Com- parative Zoology. Their courtesy in transmitting the specimens is greatly appreciated. The records of the hosts from which these chiggers were removed were provided by 0. P. Pearson.
Six species of chiggers have previously been reported from Peru: Crotiscus tizomasi (Oudenians, 1910) ;' Mega- trombicula peruvima (Ewing, 1929) ; Odontacarus au- , st ralis Ewing, 1929 ; Trow16ic1da sha& Ewing, 1929 ; Trombicula japa Ribeyro and Bambaren, 1922; and Eu- trombicula alfreddugesi tropica (Ewing, 1928). The present paper increases the list to ten. Of the six species
previously reported Megatro~~zbicula peruviana is known only as an adult while Trombicula Java cannot be identi- fied on the basis of available infornlation and will prob- ably have to become a species incerta seclis. While preparing this paper particular attention has been given to the modified setse of the legs. Wharton 1947 and 1947a has shown that the chsetotaxy of the legs is an important aid to the taxonomic study of larval trom- biciilids. As more and more species are studied, it be- comes increasingly obvious that it is desireable to name these setze. Grandjean 1935 worked out a system of no- menclature for the modified seta on the last three seg- ments of the legs of oribatid mites. However, his system applied to all instars and so cannot be readily modified to fit the present case.
Nesbitt 1945 has named the setze
1 This paper is the result of work done in connection with research sup- ported by a grant-in-aid from the Research Grants Division of the U. 8. Public Health Service and is published with a grant from the Museum of Comparative Zoology at Harvard College.
2 New combination based on unpublished work by H. S. Fuller. 87




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011 the tarsi of acarid mites and has thus been able to simplify their description.
In the trombiculid mites four types of modified setae are found on the legs and palps as follows : 1. Blunt striated sensory setae-one 011 the dorsal side of each tarsus of the first two pairs of legs and one at the base of the palpal tarsus 011 the ven- tral surface.
2.
Pointed striated sensory setae-on the genua and tibiae of all leg, the tarsus of leg I, and the pre- tarsi of legs I and 11. There may be on one tar- sus I11 and the palpal tarsus, but this is unusual. 3.
Microsensory setae~may be present on the genua, tibiae, and tarsi of legs I and 11.
4.
Whip-like setae~one or more may be present on telo- femur, genu, tibia, and tarsus of leg 111. Unfortunately these setae are not all constant in their positions on the legs but may vary from species to species. It is therefore impossible to name them on the basis of location. One solution to the problem is to name the fixed setae while resewing fluid terms for the others. The following system is suggested.
spur =blunt striated sensory seta on the tarsus. (The use of the term spur for this seta is adopted from Brennan 1947, Ewing in many papers
has referred to this seta as the dorsal spine, but since it is usually rounded at its tip, Brennan's term is to be preferred.)
pretarsala = the striated sensory seta on the pretarsus. subterminala = the pointed striated sensory seta on the dorsal prominence of tarsus I.
(The term subterminal is taken
from Ewing 1931.)
parasubterminala = a niicrosensory seta associated with the subterminal seta.
microspur = a microsensory seta close to the spur or situated between the spur and the sub-
terminal seta.
tibiala = a pointed striated sensory seta on the tibia. microtibiala = a micros ens or^ seta 011 the tibia.



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genuala = a pointed striated sensory seta on the genu. microgenuala = a microsensory seta on the gem. mastitarsala = a whip-like seta on the tarsus. mastitibiala = a whip-like seta on the tibia. mastigenuala = a whip-like seta on the gem. mastifemorala = a whip-like seta on the femur. By combing the names of the sete as given above with the appropriate Roman numeral to indicate the leg on Pig. 1.
Eusdiongafttia phylloti n. sp.
A, dorsum; B, venter; C, dorsal
view of gnathosoma; D, ventral view of gnathosoma; E, scutum; F, leg I with specialized set% of genu, tibia, tarsus, and pretarsus; G, similar view of leg 11; G, similar view of leg 111. (Magnification of each figure, iiidi- eated by the line associated with the figure, represents 50 microns.) which the seta or setas are found the statement, "three whip-like sets on tarsus 111" can be reduced to "three rna~tita~salse III", or the statement," a blunt striated sensory seta on tarsus 1'' can be reduced to "spur I.'' A second and perhaps more important reason for naming



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90 Psydze
[June
the modified setae on the legs is that it will call attention to their presence and importance in the descriptions of trombiculid larvae. A nameless structure is more likely to be ignored than one for which a name is available. The above system of nomenclature will be adopted in describing the four species included in this paper. Spe- cial drawings of tlie legs (Figure I) have been made so that the modified setae can be shown in detail. Euschongastia phylloti 11. sp.
Body: Oval in shape, 560 microns long and 360 wide, striae over entire surface.
A pair of subequal eyes with
well developed corneas on each side of the body at the level of the posterior lateral scutal setae. Eyes about 15 mi- crons in diameter.
Anal opening ventral.
GnatJzosoma: Chelicers~ stout, basal segments with angular lateral expansions, distal segment with a hyaline tip that bears a dorsal tooth, a minute ventral tooth, and a pointed apex. Palpal segment 1 with a feathered seta; 2 with a feathered seta; 3 with a seta that is nude or branched; 4 with a dorsal and ventral sete feathered and lateral seta nude or branched, palpal claw with two small dorso-lateral tines and one large median tine; 5 with a spur, 5 ventral feathered setae, and one dorsal feathered A ,
seta. Galeal seta nude. No stigmata or tracheae present. Legs: Coxae I and I1 contiguous, coxa I11 about its own length posterior to coxa 11. All coxae with a single seta except tlie right coxa of specimen #540-2 which has two setae.
Sensory setae on left's as follows:
-
1-2 genualae, 1 microgenuala, 2 tibiala?, 1 niicro- tibiala, 1 spur, 1 microspur lateral to the spur, 1 subterminala, 1 parasubterminala, and 1 pretarsala.
11-1 genuala, 2 tibialae, 1 spur, 1 microspiir posterior to the spur, and 1 pretarsala.
111-1 genuala and 1 tibiala.
Each leg terminates in a pair of tarsal claws that are lateral to a medium longer and thinner claw-like em- podium.




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10481 Wharton-Xew Peruvian C71iggers 91
Scutum: Roughly rectangular with punctate ornamenta- tion. A definite V-shaped ridge anterior to the pseudo- stigmata.
Posterior lateral setae on lateral projections of the scutum. Scutal set= stout and feathered. Sen- sills globose with fine setules over entire surface except on bmal portion of stem. The Standard Data (Wharton 1946) follow :
Specimen AW PW SB ASB PSI3 AP AM AL PL S 540-1 79
105 20 30 21 43
55
69
75 32
6 2 1-6
69 99
19 31 23 35 55 62 62 23
621-$Type 76
90 21 28 18 32
50
62 54
37
621-9 66 88 20 27 14 27 46 62 62 27
621-Id 69 88 18 29 20 29 44 60 62
Mean 72 94 1.9 29 19 33 50 63 63 30
Setce': Dorsal setae feathered about 55 microns long and arranged in indistinct rows, about 100 seh in all. Hu- meral set= not distinctly set off from other dorsal setae. Sternal set,= feathered, 2 pairs between cox% I and 11, about 40 microns long. Approximately 60 ventral set= arranged in indistinct rows from between COX= I11 to the posterior end, feathered, and about 50 microns long. Material: The following specimens all collected by 0. P. Pearson at Caccachwa, 50 miles S. W. of Have, Peru were studied :
0. 7'. Pcu~~son's # Host Date ATwm6er of Specimens 540 Phyllotis 5 October 2
darwini 1946
547 Chinchillvia 7 October 1
sa71an1ce 1946
621 Pliyllotis 22 October 13 + Type
clarwini 1946 (XCZ KO. 3026)
Diagnosis: Euschongastia phylloti can be readily re- cognized inlthat it differs from other members of the genus as here interpreted .in having the ventral sets extend anteriorly between coxas 111.
Rernards: Ewing restricted the genus Euschongastia to species with more than three prongs 011 the palpal claw, and erected the genus Ascoschongastia to include similar specimens with two or three prongs 011 the palpal claw. The type species of Ascoschongastia however has only



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three setae 011 the scutum instead of five. It seems more
desireable at present to expand the meaning of Eusch6n- gastia to include E. phylloti than to erect a new genus or to accept Swing's interpretation of Ascoschongastia. Trombicula pearsoni 11. sp.
Figure 2
Body: Oval, 350 microns long by 250 mcirons wide, striae fine anteriorly coarser posteriorly, eyes opposite posterior lateral scutal setae, anterior eyes larger 18 mi- crons, posterior eyes 15 microns, both eyes on an indis- tinct ocular plate, anus ventral more than its own length from the posterior end in a partially engorged specimen. Gnathosoma: Chelicerse with rounded basal segments that are longer than the narrow dorsally curved distal segments. Each distal segment with a tricuspid cap, one tooth dorsal, one ventral, and one apical. Palpal segments evenly rounded laterally;
segment 1 with a
feathered seta ; 2 with a feathered seta ; 3 with a feathered seta with fewer barbs than seta on 2; 4 with a nude dorsal seta, a branched lateral seta, and a feathered ventral seta. Palpal claw with two small outer prongs and a large median prong. Palpal segment 5 with a basal spur and seven feathered setse. Galeal seta nude or with one or two barbs. No stigmata or tracheae present.
Legs: Coxae in partially engored specimens nearly contiguous. Each coxa with a single feathered seta. Sensory setae on legs as follows :
I-a microgenuala between a pair of genulae, a micro- tibiala lateral to the posterior of two tibiake, a microspur anterior to the spur, a subter- minala and paras~bte~minala that arise from a single base, and a pretarsala.
11-one genuala, 2 tibialae, a microspur posterior to the spur, and pretarsala.
Ill-one genuala and one tibiala.
Each leg is terminated by a pair of curved claws that arise 011 the lateral tip of the pretarsus. A thin claw-like empodium is present between the claws.
Scutum: The scutum is roughly pentagonal, and is



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completely covered by small, numerous, punctae. The
pseudostigmata are small and each has a short slit in front of it about equal to its diameter. Sensillae are long filiform and have a few barbs on the distal two-fifths. Fig. 2.
Troinbicula pearsoni 11. sp. A, dorsum; B, venter; C, dorsal view of gnathosoma; D, ventral view of gnathosoma; E, scutum. (Magnification
of each figure, indicated by the line associated with the figure, represents 50 microns.)
The scutal setae are covered with short barbs. The Stan-
dard Data follow:
Specimen AW
PW
SB ASB
PSB AP
AM
AL PL S
86
118 47
52 40
54
72
51 66 97
Type 94
117
46
41
46
48 63
48 69
456-1
456-2 90 114 50 39 43 41 72 60 69' 93
-
Mean 90 116 48 44 43 48 69 53 68 95
Setce: The dorsal setae are similar to the scutal setae. They are about 85 microns long and are distributed in transverse rows from anterior to posterior as indicated



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94 Psydze [June
below.
The anterior ventral setae, including the sternal set=, differ from the dorsal setae in that t,heir barbs are slightly longer and arise from only two lines along the shaft rather than all over the shaft. The arrangement in indefinite rows is given below.
Specimen Dorsal setae
Ventral set= Total
Type
2-8-5-8-4-6-4 t 9 2-2 t 16 66
456-2
2-6-2-8-7-7-4
+14 2-2 + 16 7 0
456-1
2-8-6-8-6-8 + 18 2-2 + 18 78
Material: These specimens were collected by 0. P. Pear- son at Caccachara, 50 miles S.W. of Have, Peru, at an elevation of 16,000 feet.
0. P. Pearson's # Host Date Number of Specimens 456 Pzino mys 13 September 2 + Type
lemmimis 1946 (MCZ KO. 3027)
Diagnosis: Trombicztla pearsoni can be distinguished from other members of the genus because while it has a pentagonal scutum it lacks whip-like setae on the t,hird legs. In these characteristics it is similar to Trombicula .hi& n. sp. but can be distinguished from it most readily on the basis of the feathered dorsal seta on the palpal tibia in T. biops? as opposed to the nude seta found in this position in T. pearsoni.
Remarks: This species is named for the collector 0. P. Pearson.
Trombicula biops 11. sp.
Figure 3
Body: Elongated 462 microns by 200 microns, strise well developed, eyes two on either side at the level of the posterior lateral setae. No ocular plate present. Diam- eter of anterior eye 10 microns, posterior eye 8 microns. Anus about twice its length from the posterior end on the ventral side.
Gnathosoma: Basal segments of chelicerae weakly angu- lar laterally, distal segments short with tricuspid cap. Palpal segment 1 with a feathered seta; 2 with a feathered seta; 3 with a feathered seta; 4 with two branched setae and a ventral feathered set,a, palpal claw with two small subequal dorso-lateral prongsand a stout longer median



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96 Psyche
[June
genuala, a tibiala, but no whip-like setae. Each leg is
terminated by a pair of lateral anibulacral claws that flank a median longer and thinner claw-like empodium. Scutum: The scutum is definitely pentagonal in shape. It is ornamented by closely set, irregularly placed puiictae. The pseudostigmata are small and bordered by short anterior and posterior ridges. The sensillae are peculiar in that they have extremely short fine barbs along- their entire length. The scutal setae are provided with short barbs over their entire surface. The Standard Data follow :
Specimen AW
PW
SB ASB PSB AP AM AL PL S
Type 70
86 28 35
41 30 48
40 59 72
508-1 69 90 25 35 39 29 46 44 62 83
5 0 8-2 70 89 28 35 36 26 41 39 57 75
5 0 8-4 72 91 26 35 36 31 48 35 58 76
540-2 67 79 26 28 29 25 35 29 47 ...
Setce: Dorsal and ventral setae similar to scutal setae about 40 to 50 microns long. Dorsal setae irregularly arranged.
A pair of humeral setae present followed by an irregular band of about 16 setae, behind these anterior dorsal setae there are about 40 posterior dorsal setae. The ventral setae are arranged in more definite rows than the dorsal setae but they are also too irregular to permit a setal formula. Two pairs of sternal setae in all eight specimens examined but the type is unusual in that it bears an extra median seta between the first pair of sternal setae. Posterior to the last pair of coxae there are about 40 set& arranged in irregular rows. Material: Collected by 0. P. Pearson at Caecacham, 50 miles S.W. of Have, Pern, at an altitude of 16,000 feet. 0. P. Pearson's # Host Date Mber of Specimens Phyllotis 28 September s
508 boliviensis 1946
540 Ph yllotis 5 October 2 + Type
darwini 1946 (MGZ Xo. 3029) .
Diagnosis : As mentioned under the discussion of Tro m- bicula pearsoni, T. biops is morphologically similar to it. 2'. biops can be separated from T. pears06 on the shape



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19481 Wharton-New Peruvian CJiiggers
Fig. 4. fiom'bieula cham 11. sp. A, dorsum; B, venter; C, dorsal view of gnathosoma; D, ventral view of gnathosoma; E, scutum. (Magnification of each figure, indicated by the line associated with the figure, represents 50 microns.)
of the scutum, absence of ocular plates, size of the sub- terminalae, and arrangement of the body set~ as well as by the difference noted under the discussion of T. pear- soh.




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[June
Remarks: The sensory setae and sensillae of this species are so different. from those of other species that have been studied in this respect, that it is difficult to know just how T. biops is related to other species. Trombicula chara 11. sp.
Figure 4
Body: An enlongated regular oval 625 microns long by 400 microns wide. Striae weak. Eyes distinctly sepa- rate ; anterior eyes 8 microns in diameter, posterior eyes 6 microns. Anus ventral and relatively far anterior, 170 microns from the posterior end.
Gnathosoma: Chelicerae with rounded basal segments, and short strongly curved distal segments each of which terminates in a typical tricuspid cap. Palpal segments 1 and 2 with feathered setae; segment 3 with a branched seta ; the three setae on segment4 branched, palpal claw with two subequal dorso-lateral tines and a longer median ventral prong; segment 5 with a basal spur and seven feathered setae, one dorsal, two apical, and four ventral. Galeal seta branched. No stigmata or tracheae present. Legs: Coxae I and 11 contiguous, coxa I11 separated by its own length from coxa 11.
All coxae with a single
feathered seta. Leg I with three genualae, one micro- genuala, two tibialae, one microtibiala, one spur, one micro- spur at the tip of the spur, one subterniinala and one - ,
parasubterminala arising from the same base, and one pretarasala. Leg I1 with one genuala, two tibialae, one spur, and a pretarsala.
Leg I11 with one genuala, one
tibiala, and one niastitarsala.
All legs terminate in a
pair of claws and a median claw-like empodium. Scutwi
mar gin.
anterior
Sensillae
2; Irregularly shaped with a sinuous posterior Punctae scattered over entire scutum except 011