Parathalassius Mik

Cumming, Jeffrey M., 2017, Revision of the Nearctic Parathalassius Mik (Diptera: Dolichopodidae: Parathalassiinae), with a review of the world fauna, Zootaxa 4314 (1), pp. 1-64 : 9-11

Genus Parathalassius Mik

Parathalassius Mik, 1891: 217 (nec Dussart 1986). Type species: Parathalassius blasigii Mik , by original designation.

Diagnosis. Body covered with dense pale pruinosity that gives a grey or brownish-grey appearance; prosternum fused with proepisternum to form precoxal bridge; scutellum with 2–3 pairs of marginal bristles; tarsi with apex of tarsomere 5 lacking medial finger-like process; wing with pterostigma indistinct, anal lobe weakly to partially developed, cell dm present, cell cua truncate apically with CuA straight or nearly straight, vein CuA+CuP short to relatively long; hypopygium globular, about 1/3–1/2 length of abdomen, asymmetrical with hypopygial foramen not formed, left ventral epandrial process present and basally articulated, bifurcate or unbranched, ventral lobe of left surstylus with complex upturned projection arising medioventrally, right epandrial lamella not fused to right side of hypandrium, dorsal lobe of right surstylus usually with frayed prensiseta on medial surface, hypandrium reniform and broadly notched posteriorly where phallus protrudes, left and right postgonite lobes complex and protruding out from between dorsal and ventral surstylar lobes, phallus tubular and bent upwards with ventral spurlike projection near base, ejaculatory apodeme keel-like and laterally flattened, hypoproct projected as pair of lobes below cerci, cerci well-sclerotized and asymmetrical with right cercus larger than left cercus, female terminalia partially retracted into segment 5 with tergite 10 medially divided into 2 subtriangular hemitergites with each bearing 2 or rarely 3 flattened and blunt-tipped acanthophorite spines apically.

Redescription. Male: Body length 1.5–3.9 mm, wing length 1.4–3.5 mm. Dark brown ground colour mostly covered with dense greyish-white or brownish-grey pruinosity, with golden-yellow pruinosity on head of certain species. Setae and pubescence of body and legs white, yellow, brown, or golden. Head ( Figs 23, 25–30, 33–36 ): Ovoid in lateral view, slightly broader than high in anterior view. Neck inserted slightly above middle of head. Ocellar triangle conspicuous. Occiput weakly concave on upper median part above occipital foramen. Dichoptic; eyes entirely covered with ommatrichia, medial edge with weak emargination adjacent to antenna; ommatidia slightly smaller anterodorsally. Frons greyish, over 2X broader than high, widening above. Face narrowest at middle, about 1.75–2.75X width of anterior ocellus. Clypeus not separated from face; about as high as broad, widening below; apical margin truncate, weakly produced. Bristles of head well-differentiated; dorsal bristles strong: 1 pair of inclinate fronto-orbitals well-separated from base of antenna and arising lateral to anterior ocellus, 1 pair of lateroclinate anterior ocellars, 1 pair of small posterior ocellars, 1 pair of strong widely spaced inclinate postocellars, 2–4 pairs of lateroclinate verticals; postocular setae short and mainly uniserial; postgena with longer scattered setae usually extending onto gena around edge of mouth-opening. Gena narrow. Antenna ( Figs 38–42, 44–47 ) brown to dark brown, inserted above middle of head in profile; scape short, funnel-shaped; pedicel subequal in length to scape, spheroidal with subapical circlet of setulae; postpedicel short-subtriangular, subtriangular, subquadrate, or elongate-conical, 1.25–1.8X longer than wide, clothed in fine setulae, sensory pit present on outer lateral surface; arista-like stylus about 1.4–2.0X length of postpedicel, with minute hairs. Palpus ovoid apically, dark brown, clothed with minute pile, apical half with several short setae on outer surface, sensory pit present. Proboscis short, projecting ventrally; epipharyngeal carina present; epipharyngeal blades narrow; labellum with 6 geminately sclerotized pseudotracheae. Thorax: Mesoscutum slightly arched, prescutellar depression apparent. Prosternum fused with proepisternum forming precoxal bridge. Proepisternum with 1–2 setulae per side. Antepronotum narrow with 3–4 setulae per side. Postpronotal lobe distinct with several small setulae (with one distinct short bristle in P. ulrichi Shamshev ). Mesonotum shield-shaped in dorsal view, longer than wide, bristles well-differentiated. Acrostichal setulae present, biserial or quadriserial, not extended posteriorly onto prescutellar depression; 5–8 dorsocentral bristles (posteriormost bristle strongest), 0–2 presutural intra-alar bristles, 1–2 presutural supra-alar (posthumeral) bristles, 2–4 postsutural supra-alar bristles, 2–4 notopleural bristles, and 1 postalar bristle per side, with accessory setulae between rows. Scutellum crescent-shaped in dorsal view with 2–3 pairs of marginal bristles, subapical pair longest. Mesopleuron bare. Halter pale yellowish-white. Legs: Mostly clothed with pale setae or setulae, tarsal claws, pulvilli and empodium normally developed on all legs. Foreleg: Coxa with numerous setae on anterior surface. Femur slightly longer than tibia, with well-developed setae on posterior surface, setae shorter on anterior surface. Tibia slender. Tarsus slightly longer than tibia; tarsomere 1 slightly shorter than combined length of tarsomeres 2–5, apparently lacking spinose anterior tubercle at base; tarsomeres 2–4 decreasing in length apically; tarsomere 5 subequal in length to tarsomere 3, apex lacking medial finger-like process. Midleg: Coxa with several setae on anterior surface. Femur slightly shorter than tibia, with well-developed setae on anterior surface and few short setae on posterior surface. Tibia slender with at least 1 apicoventral bristle. Tarsus longer than tibia; tarsomere 1 slightly shorter than combined length of tarsomeres 2–5; tarsomeres 2–4 decreasing slightly in length apically; tarsomeres 1–4 each with dark spine-like apicoventral setae; tarsomere 5 subequal in length to tarsomere 3, apex lacking medial finger-like process. Hindleg: Coxa with 2–4 setae on outer surface. Femur slightly longer than tibia, with well-developed setae on anterior surface and few short setae on posterior surface. Tibia slender. Tarsus of variable length, slightly shorter, subequal, or longer than tibia; tarsomere 1 shorter than combined length of tarsomeres 2–4, with minute spinose posteroventral tubercle at base; tarsomeres 2–4 usually decreasing in length apically; tarsomere 5 usually subequal in length to tarsomere 3 (or 4 in certain species), apex lacking medial finger-like process. Wing ( Figs 56–60, 62, 64–67 ): Hyaline to infuscate with yellowish to dark brown veins, about 2.5–3.0X longer than wide. Pterostigma indistinct, membrane entirely covered with minute microtrichia. Anal lobe partially developed (weakly developed in P. infuscatus sp. nov.), alula absent. Costa circumambient. Extreme anterior base of costa with short row of anterodorsal setae, apical seta strongest. Anterior costal section bearing row of short spine-like setae intermixed with fine setae from Sc to R2+3, posterior part of costa beyond R2+3 with only fine setae. Longitudinal veins complete (except CuA+CuP), reaching wing margin. Sc faint apically. R1 straight, reaching costa beyond middle of wing (or beyond base of M2). Base of Rs originating opposite humeral crossvein. R2+3 diverging from R4+ 5 in basal half, running nearly parallel to R4+ 5 in distal half. R4+5 straight. M1 running nearly parallel to R4+5 beyond cell dm. M2 and M4 nearly straight and subparallel beyond cell dm. Costal section between M1 and M2 distinctly longer than costal section between M2 and M4. Short r-m crossvein present in basal portion of wing, distal to base of R4+5. Crossvein bm-m incomplete. Cell dm present, closed by base of M2 and crossvein dm-m, cell extended to middle of wing. Cells br, bm and cua in basal fourth of wing. Cells bm and cua broader than br. Cell cua closed, truncate apically with CuA straight or nearly straight. Vein CuA+CuP short to relatively long. Calypter with fine setae. Abdomen: Abdominal muscle plaques present, prominent on lateral margins of tergites 2–4; tergite and sternite 2 with transverse band of muscle plaques anteriorly. Tergite 1 with short fine setae; sternite 1 bare. Tergites 2–6 clothed with well-developed setae (setae on tergites 5 and 6 sometimes restricted to posterior margin); sternites 2–4 clothed with short weaker setae; sternite 4 usually with posterior edge emarginate; sternite 5 usually with short setae present near posterior margin; sternite 6 with short sparse setae present; tergite 7 usually bare, sometimes with 1–2 setae present; sternite 7 usually bare, sometimes with 1–2 or occasionally several setae present. Segment 1 reduced and very short; segments 2–4 mostly symmetrical with simple tergites and sternites, segment 2 relatively long; segments 5–7 narrowed, somewhat more heavily sclerotized (especially segments 6 and 7) and laterally compressed to form cavity on right side for hypopygium. Sternite 5 with or without projecting pregenitalic process, with desclerotized region medially or with posterior edge deeply and/or broadly emarginate (behind pregenitalic process if present). Sternite 8 subquadrate to subrectangular, forming dome-like cap over anterodorsal region of hypopygium, setose with some marginal setae stronger; tergite 8 reduced to narrow band-like sclerite, or indistinct and partially to mostly membraneous medially. Hypopygium ( Figs 68–126 ): Lateroflexed to right; inverted with posterior end directed anteriorly; globular, about 1/3–1/2 length of abdomen; asymmetrical; hypopygial foramen not formed. Epandrium divided into left and right lamellae. Left epandrial lamella narrowly constricted at middle with broad dorsal and ventral portions, ventral epandrial portion partially overlapping left side of hypandrium with lower margin distinct but fused to hypandrium; ventral epandrial process ( Figs 80–94 ) present, basally articulated, bifurcate or unbranched (dorsal arm absent), ventral arm with minute apicodorsal seta and 1–2 minute to small setae along lateroventral margin, apex of most species with expanded lamelliform concavity, apex of certain species laterally flattened and narrow with ventral edge and medial surface serratulate. Left surstylus with dorsal and ventral lobes separated by shallow U-shaped cleft through which left postgonite lobe protrudes. Dorsal lobe of left surstylus with 1 basidorsal seta and 1 basilateral seta, most species with apical seta and knob- or stalk-like medial projection present. Ventral lobe of left surstylus with complex upturned projection arising medioventrally. Right epandrial lamella partially overlapping right side of hypandrium, not fused with hypandrium; apical portion of epandrial lamella broad with ventral epandrial process present or absent; basal portion of epandrial lamella narrowed with variably developed emargination bordering ventral margin of right cercus. Right surstylus with dorsal and ventral lobes separated by deep cleft through which right postgonite lobe protrudes. Dorsal lobe of right surstylus with 3 lateral or marginal setae, apex narrowed with thick apically-frayed prensiseta on medial surface in most species.

Ventral lobe of right surstylus projecting dorsally. Hypandrium reniform with posterior end broadly notched where phallus protrudes. Postgonite with basal internal portion cradling base of phallus; left and right postgonite lobes complex, protruding out from between dorsal and ventral surstylar lobes. Phallus ( Figs 95–114 ) tubular, bent upwards, well-sclerotized, basal internal portion with ventral spur-like projection abutting medioventral margin of postgonite cradle, distal external portion varying in length, curvature and armature. Ejaculatory apodeme keel-like, laterally flattened, subrectangular to broadly subtriangular in lateral view. Hypoproct projected as pair of usually slender lobes below cerci. Cerci ( Figs 115–126 ) well-sclerotized, asymmetrical, medial margin of each cercus with longitudinal row of 3 setae adjacent anal region (anal setae), right cercus larger than left cercus, with basal portion distended and rounded laterally in most species.

Female: Body length 1.9–4.3 mm, wing length 1.5–4.0 mm. Similar to male except as follows: Pruinosity and setae of head concolourous with pruinosity and setae of body. Head ( Figs 24 , 31–32, 37 ): Face wider, at middle about 3.0–5.0X width of anterior ocellus. Legs: Setae on fore, mid and hindleg somewhat less developed, with individual setae slightly shorter and more slender. Wing ( Figs 61, 63 ): Hyaline, with at most slight shading at apex of cell dm (infuscate like male, in one species). Abdomen ( Figs 127–132 ): Tapering posteriorly, apical segments partially retracted into segment 5. Tergites 2–5 clothed with well-developed setae, setae slightly weaker and less erect than in males of most species; sternites 2–5 clothed with short weaker setae. Terminalia with tergite 6, segments 7 and 8 usually glabrous (except for a few minute setulae), sternite 6 setose (at least on posterior portion); tergite 6 broader than long with anterior edge broadly or deeply emarginate; sternite 6 broader than long, subrectangular; tergite 7 usually broader than long with anterior edge deeply emarginate; sternite 7 broader than long and usually with anterior edge (and sometimes posterior edge) broadly emarginate; tergite 8 divided medially, articulated with sternite 8 anterolaterally; sternite 8 trough-like or plate-like, apical portion with well-developed ridges in certain species ( Figs 133–141 ); sternite 9 variably developed; spermatheca developed as unpigmented membraneous sac-like terminal expansion of spermathecal duct; spermathecal duct narrow elongate and coiled, arising from broad ridged sperm pump; tergite 10 medially divided into broad subtriangular hemitergites, each with 2 or rarely 3 flattened and blunt-tipped acanthophorite spines apically and 1–3 setae laterally; sternite 10 narrow and V-shaped, weakened or divided medially, with 1 small seta per side; cercus well-sclerotized, setose, with apex pointed or blunt-tipped.

Immatures: Nothing is known of the eggs, larvae, or pupae.

Included species, distribution and habitat. The genus is Holarctic in distribution and currently comprises 15 species (including the new species described herein). All species of Parathalassius occur on sandy sea coasts ( Figs 11–22 ). Most species appear restricted to fore dune beach habitats on either wet or loose sand, or on associated beach vegetation. Some species however (e.g., P. aldrichi Melander , P. sinclairi sp. nov.), also occur in remnant back dune habitats that border the fore dune beaches. The Palaearctic fauna includes the type species Parathalassius blasigii Mik from the western Mediterranean and Azores ( Chvála 1988, 1989), and two species ( P. maritimus Shamshev and P. ulrichi Shamshev ) from the Russian Far East (Kuril Islands) ( Shamshev 1998) and now Japan. The Nearctic fauna includes Parathalassius abela sp. nov., P. aldrichi Melander , P. candidatus Melander , P. dilatus sp. nov., P. infuscatus sp. nov., P. melanderi Cole , P. midas sp. nov., P. sinclairi sp. nov., P. socali sp. nov., P. susanae sp. nov., P. uniformus sp. nov. and P. wheeleri sp. nov., all of which occur on the Pacific coast of North America ( Figs 142–153 ). Parathalassius susanae sp. nov. is also known from a single locality on the Atlantic coast of the USA (Sapelo Island, Georgia) ( Fig. 151).

Figures

FIGURES 23 – 28. Heads of Nearctic Parathalassius in anterior view. 23. Parathalassius abela sp. nov., male. 24. Parathalassius abela sp. nov., female. 25. Parathalassius wheeleri sp. nov., male. 26. Parathalassius candidatus Melander, male. 27. Parathalassius infuscatus sp. nov., male. 28. Parathalassius melanderi Cole, male.

FIGURES 29 – 37. Heads of Nearctic Parathalassius. 29 – 30. Parathalassius midas sp. nov., male, anterior and lateral views. 31 – 32. Parathalassius midas sp. nov., female, anterior and lateral views. 33. Parathalassius sinclairi sp. nov., male, anterior view. 34. Parathalassius socali sp. nov., male, anterior view. 35. Parathalassius susanae sp. nov., male, anterior view. 36. Parathalassius uniformus sp. nov., male, anterior view. 37. Parathalassius uniformus sp. nov., female, anterior view.

FIGURES 38 – 47. Antennae of Nearctic Parathalassius (male left antenna in medial view, unless otherwise noted). 38. Parathalassius abela sp. nov. 39. Parathalassius wheeleri sp. nov. 40. Parathalassius candidatus Melander. 41. Parathalassius infuscatus sp. nov. 42. Parathalassius melanderi Cole, right antenna in lateral view. 43. Parathalassius midas sp. nov., female. 44. Parathalassius sinclairi sp. nov. 45. Parathalassius socali sp. nov., right antenna in lateral view. 46. Parathalassius susanae sp. nov. 47. Parathalassius uniformus sp. nov. Abbreviations: ar styl—arista-like stylus; ppedpostpedicel.

FIGURES 56 – 67. Wings of Nearctic Parathalassius. 56. Parathalassius abela sp. nov., male. 57. Parathalassius wheeleri sp. nov., male. 58. Parathalassius candidatus Melander, male. 59. Parathalassius infuscatus sp. nov., male. 60. Parathalassius melanderi Cole, male. 61. Parathalassius melanderi Cole, female. 62. Parathalassius midas sp. nov., male. 63. Parathalassius midas sp. nov., female. 64. Parathalassius sinclairi sp. nov., male. 65. Parathalassius socali sp. nov., male. 66. Parathalassius susanae sp. nov., male. 67. Parathalassius uniformus sp. nov., male. Abbreviations: bm-m—basal medial crossvein; cuaanterior cubital (= anal) cell; CuA—anterior branch of cubital vein; CuP—posterior branch of cubital vein; dm—discal medial cell; dm-m—discal medial crossvein; h—humeral crossvein; M 1, M 2, M 4 — medial veins; R 1, R 2 + 3, R 4 + 5 — radial veins.

FIGURES 68 – 71. Male terminalia of Parathalassius sinclairi sp. nov. 68. Ventral view. 69. Dorsal view. 70. Left lateral view. 71. Right lateral view. Abbreviations: cerc—cercus; epand—epandrium; hypd—hypandrium; hyprct—hypoproct; pgtpostgonite; st—sternite; tg—tergite; v epand proc—left ventral epandrial process.

FIGURES 72 – 75. Dorsal lobe of left surstyli and hypopygia of Nearctic Parathalassius. 72. Parathalassius wheeleri sp. nov., apex of dorsal lobe of left surstylus, lateral view. 73. Parathalassius aldrichi Melander, apex of dorsal lobe of left surstylus, lateral view. 74. Parathalassius aldrichi Melander, hypopygium, left lateral view. 75. Parathalassius aldrichi Melander, hypopygium, right lateral view. Abbreviations: cerc—cercus; d sur—dorsal lobe of surstylus; epand—epandrium; hypdhypandrium; hyprct—hypoproct; pgt lb—postgonite lobe; ph—phallus; v epand proc—left ventral epandrial process; v surventral lobe of surstylus. Scale bars = 0.1 mm.

FIGURES 76 – 77. Hypopygium of Parathalassius midas sp. nov. 76. Left lateral view. 77. Right lateral view. Abbreviations: cerc—cercus; d sur—dorsal lobe of surstylus; epand—epandrium; hypd—hypandrium; hyprct—hypoproct; pgt lb—postgonite lobe; ph—phallus; v epand proc—left ventral epandrial process; v sur—ventral lobe of surstylus. Scale bar = 0.1 mm.

FIGURES 78 – 79. Hypopygium of Parathalassius sinclairi sp. nov. 78. Left lateral view. 79. Right lateral view. Abbreviations: cerc—cercus; d sur—dorsal lobe of surstylus; epand—epandrium; hypd—hypandrium; hyprct—hypoproct; pgt lb—postgonite lobe; ph—phallus; v epand proc—left ventral epandrial process; v sur—ventral lobe of surstylus. Scale bar = 0.1 mm.

FIGURES 80 – 94. Left ventral epandrial processes of Nearctic Parathalassius, lateral view (unless otherwise noted). 80. Parathalassius abela sp. nov. 81. Parathalassius candidatus Melander. 82. Parathalassius sinclairi sp. nov. 83. Parathalassius susanae sp. nov. 84. Parathalassius susanae sp. nov. 85. Parathalassius dilatus sp. nov. 86. Parathalassius melanderi Cole. 87. Parathalassius infuscatus sp. nov. 88. Parathalassius midas sp. nov. 89. Parathalassius socali sp. nov. 90. Parathalassius socali sp. nov., ventrolateral view. 91. Parathalassius uniformus sp. nov. 92. Parathalassius aldrichi Melander. 93. Parathalassius wheeleri sp. nov. 94. Parathalassius wheeleri sp. nov. Scale bars = 0.1 mm.

FIGURES 95 – 102. Phallus of Nearctic Parathalassius species. 95. Parathalassius abela sp. nov., entire phallus, left lateral view. 96. Parathalassius abela sp. nov., distal portion, posterior view. 97. Parathalassius sinclairi sp. nov., distal portion, left lateral view. 98. Parathalassius sinclairi sp. nov., distal portion, posterior view. 99. Parathalassius melanderi Cole, distal portion, left lateral view. 100. Parathalassius melanderi Cole, distal portion, posterior view. 101. Parathalassius dilatus sp. nov., distal portion, left lateral view. 102. Parathalassius dilatus sp. nov., distal portion, posterior view. Abbreviations: ej apod—ejaculatory apodeme; v spur—ventral spur-like projection. Scale bars = 0.1 mm.

FIGURES 103 – 110. Phallus of Nearctic Parathalassius species. 103. Parathalassius aldrichi Melander, entire phallus, left lateral view. 104. Parathalassius aldrichi Melander, distal portion, posterior view. 105. Parathalassius wheeleri sp. nov., entire phallus, left lateral view. 106. Parathalassius wheeleri sp. nov., distal portion, posterior view. 107. Parathalassius socali sp. nov., entire phallus, left lateral view. 108. Parathalassius socali sp. nov., distal portion, posterior view. 109. Parathalassius uniformus sp. nov., distal portion, left lateral view. 110. Parathalassius uniformus sp. nov., distal portion, posterior view. Abbreviations: ej apod—ejaculatory apodeme; v spur—ventral spur-like projection. Scale bars = 0.1 mm.

FIGURES 111 – 114. Phallus of Nearctic Parathalassius species. 111. Parathalassius infuscatus sp. nov., distal portion, left lateral view. 112. Parathalassius infuscatus sp. nov., distal portion, posterior view. 113. Parathalassius midas sp. nov., distal portion, left lateral view. 114. Parathalassius midas sp. nov., distal portion, posterior view. Abbreviation: v spur—ventral spurlike projection. Scale bars = 0.1 mm.

FIGURES 115 – 120. Male cerci of Nearctic Parathalassius, dorsal view. 115. Parathalassius abela sp. nov. 116. Parathalassius candidatus Melander. 117. Parathalassius susanae sp. nov. 118. Parathalassius sinclairi sp. nov. 119. Parathalassius infuscatus sp. nov. 120. Parathalassius midas sp. nov. Abbreviation: hyprct—hypoproct. Scale bars = 0.1 mm.

FIGURES 121 – 126. Male cerci of Nearctic Parathalassius, dorsal view. 121. Parathalassius aldrichi Melander. 122. Parathalassius wheeleri sp. nov. 123. Parathalassius socali sp. nov. 124. Parathalassius uniformus sp. nov. 125. Parathalassius melanderi Cole. 126. Parathalassius dilatus sp. nov. Abbreviation: hyprct—hypoproct. Scale bars = 0.1 mm.

FIGURES 127 – 132. Female terminalia of Nearctic Parathalassius. 127. Parathalassius midas sp. nov., lateral view. 128. Same, dorsal view. 129. Same, ventral view. 130. Parathalassius sinclairi sp. nov., lateral view. 131. Same, dorsal view. 132. Same, ventral view. Abbreviations: st—sternite; tg—tergite.

FIGURES 133 – 141. Female sternite 8 of Nearctic Parathalassius, ventral view. 133. Parathalassius abela sp. nov. 134. Parathalassius midas sp. nov. 135. Parathalassius candidatus Melander. 136. Parathalassius melanderi Cole. 137. Parathalassius sinclairi sp. nov. 138. Parathalassius uniformus sp. nov. 139. Parathalassius socali sp. nov. 140. Parathalassius aldrichi Melander. 141. Parathalassius susanae sp. nov. Scale bar = 0.1 mm.

FIGURES 11 – 16. Collection localities and habitats of Nearctic Parathalassius. 11. Island View Beach, British Columbia. 12. Sidney Spit, British Columbia. 13 – 14. Cape Disappointment, Washington. 15. Bandon, Oregon. 16. Samoa Dunes Recreation Area, California.

FIGURES 17 – 22. Collection localities and habitats of Nearctic Parathalassius. 17 – 18. Morro Bay, California. 19. Surf Beach, California. 20. Surf Beach, California, with biologist and photographer Alice Abela collecting Parathalassius from a patch of beach bur, Ambrosia chamissonis (Less.) Greene. 21. Crystal Cove State Park, California. 22. Crystal Cove State Park, California, vegetation at back of beach.

FIGURES 142 – 144. Known geographical distributions of Nearctic Parathalassius. 142. Parathalassius abela sp. nov. 143. Parathalassius aldrichi Melander. 144. Parathalassius candidatus Melander.

FIGURES 145 – 147. Known geographical distributions of Nearctic Parathalassius. 145. Parathalassius dilatus sp. nov. 146. Parathalassius infuscatus sp. nov. 147. Parathalassius melanderi Cole.

FIGURES 148 – 150. Known geographical distributions of Nearctic Parathalassius. 148. Parathalassius midas sp. nov. 149. Parathalassius sinclairi sp. nov. 150. Parathalassius socali sp. nov.