76 



Scott; Aquatic Collembola 



Mounting. — After clearing in clove oil, specimens 

 may be transferred directly to the slide-mounting 

 medium. Euparal and hyrax have proven very satis- 

 factory; Canada balsam darkens with age whereas the 

 other two do not. Since it may be necessary to examine 

 specimens under the oil immersion objective, no. 1 

 cover-glass circles should be used, and only mild 

 heat, if any, should be used to cure the slides. The 

 medium will usually set to durable strength in a month 

 or six weeks at room temperatures. 



Key to the California families of Aquatic Collembola 



1. Body elongate, thorax and abdomen distinctly separated, 

 abdominal segmentation distinct except for posterior 

 fusion in some species (fig. 2:2a, b). suborder ARTHRO- 

 PLEONA 2 



— Body conspicuously subglobular, not distinctly seg- 

 mented except for 5th and 6th abdominal segments 

 which are usually distinct (fig. 2=2e) suborder SYMPHY- 

 PLEONA SMYNTHURIDAE 



2. Prothorax well developed, visible dorsally, and similar 

 to other segments, furnished with hairs; cuticle granular, 

 superfamily PODUROIDEA 3 



— Prothorax not distinct, usually hidden, not hairy; cuticle 

 smooth, hairy, or scaled, superfamily ENTOMOBRYOI- 

 DEA ' 5 



3. Pseudocelli absent on thorax or abdomen 4 



— Pseudocelli present on thorax and abdomen (fig. 2:2a) 

 ONYCHIURIDAE 



4. Head hypognathous; ocelli on back part of head; dentes 

 annulated distally, reaching beyond ventral tube when 

 retracted (Podura aquatica Linneaus 1758).PODURIDAE 



— Head prognathous; ocelli, if present, on fore part of 

 head; dentes not annulated, usually not reaching ventral 

 tube when retracted HYPOGASTRURIDAE 



5. Hind coxae with specialized area of fine hairs; inner 

 edge of claw with a basal groove 



ENTOMOBRYIDAE 



— Hind coxae without specialized area of fine hairs; 



inner edge of claw without groove 



ISOTOMEDAE 



Family ONYCHIURIDAE 



Key to the Genera 



1. Two sensory clubs of 3rd antennal segment curved 

 together Tullbergia Lubbock 1876 



— Two sensory clubs of 3rd antennal segment not curved 



toward each other 



Onychiurus Gervais 184 1 



Genus Onychiurus Gervais 1841 



1. Anal spines absent; tubercles of postantennal organs 

 compound, with many branched tubercles (fig. 2:3i>); 

 color white; pseudocelli present on all segments; 

 length 1.8-2.1 mm.; cosmopolitan, stagnant water, fish 

 ponds, and rain pools fimetarius (Linneaus) 1767 



— Anal spines present; tubercles of postantennal organ 

 simple 2 



2. Postantennal organs with 18-44 tubercles, closely set 

 but not crowded together; 3 pseudocelli at base of each 

 antenna arranged in triangles; unguiculus as long as 

 unguis; color white; cosmopolitan, rain pools, and 

 stagnant water armatus (Tullberg) 1869 



— Postantennal organs with 8-14 separated tubercles; 1 

 pseudocellus at base of each antenna; unguiculus two- 

 thirds as long as unguis; California, Oregon, Washing- 

 ton, on snow or water at 6,000 feet or higher 



cocklei Folsom 





Fig. 2:3. o-e, postantennal organ; f, g, apex of tibiotarsus, 

 a,Tullbergia sp.; b, Onychiurus fimetarius; c, Pseudachorutes sp. 

 d, Anurida granaria; e, Isotoma sp.; f, Smynthurinus aureus; g 

 Entomobrya sp. 



Family PODURIDAE 



This family is represented by only a single genus anc 

 species, Podura aquatica Linneaus 1758. The head is 

 hypognathous, claws long and slender, color rec 

 brown to black. The mucrones are trilamellate anc 

 granular. This is a cosmopolitan species found on 

 stagnant water. 



Family HYPOGASTRURIDAE 

 Key to the Genera 



1. Mouth parts adapted for chewing; mandibles with well- 

 developed molar plate 2 



— Mouth parts adapted for piercing and sucking; mandibles 

 without molar plate 3 



2. Postantennal organ present, eyes 8 on each side. Fur- 

 cula present Achorutes Templeton 1835 



— Postantennal organ absent, eyes 5 on each side .... 



Xenylla Tullberg 1869 



3. Anal spines present Odontella Schffr. 1897 



— Anal spines absent 4 



4. Ocelli 5 on each side; body elongate 



Anurida Laboulbene 1865 



Ocelli 8 on each side; body stout; furca present, but 

 stout and short; not aquatic 



Pseudachorutes Tullberg 1871 



Genus Xenylla Tullberg 1869 

 1. Dentes and mucrones fused, not readily differentiated 



