270 PROCEEDlNaS OF THE XATIOSAL MUSEUM. vol.49. 



Hills. This is an elevated plateau cut into table-like buttes by the 

 narrow and abrupt canyons of Satus Creek and its tributaries. This 

 arid region slopes rapidly northeast from the KHcldtat Mountains 

 on the west to the Yakima Kiver, so that, in its length of 60 miles 

 from the eastern spurs of the Klickitats to the Yakima River, Satus 

 Creek has a fall of about 3,500 feet. This is one of the most arid 

 regions of the Yakima Valley, having an annual rainfall of less than 10 

 inches, which with its rapid slope makes it so dry that it is a red and 

 brown region ^vith its naked surface but Httle reUeved by the soft gray 

 of sage bushes. Because of this aridity Satus Creek is dependent for 

 its water on the melting snows of the IQickitat Mountains, which 

 give it a flood in May and June, while it becomes almost dry from 

 July to October. 



The past summer's collecting was done o^ the lower portion of the 

 creek where Satus Canyon opens out onto the greasewood flats of 

 the Yakima River. The soil of this flat is from 5 to 10 feet deep, 

 below wliich is gravel. In crossing this flat Satus Creek has cut 

 down through the superficial layer of sod, so that it flows over the 

 surface of the gravel, having thus made an earth-walled channel 200 

 feet Avide, the floor of which is an almost continuous succession of 

 gravel bars. During flood the creek occupies the full width of the 

 channel, but during summer it dwindles to a 10 second-foot stream 

 meandering among the gravel bai-s of its flood bed.- While the 

 greasewood flat is destitute of trees, the creek itself is marked by 

 the green line of willows, eldere, alders, and balsam trees, which 

 have gained a foothold on the older gravel bars within the flood 

 channel. 



On June 17, 1913, when I made my first trip to Satus this season, 

 I searched carefully for Argias, but found none. The creek was 

 still at a medium stage, being about knee-deep on the riflles, though 

 many of the higher gravel bars were exposed. On June 26 Argias 

 were common, especially on those gravel bars grown up thickly \vith 

 young willow sprouts, for none appeared at first on the more exposed 

 bars and liffles. Many of these were beyond the teneral stage. At 

 tliis time there were flying on the creek Agrion aequahile, which had 

 been on the wing but a few days, Enallagma cyathigerum, which was at 

 the height of its season, Enallagma carunculatum at the beginning of 

 its season, Ischnura perparva common, Ischnura cervula less common, 

 ArnpTiiagrion saucium scarce and at the end of its season, OpTiio- 

 gompTius severus common and in perhaps the third week of its season, 

 Ophiogomplius occidentis rare, Aeshna californica at the end of its 

 season, Aeshna multicolor common, Sympetrum madidum at the 

 begimiing of its season, Erythemis simplicicoUis, LiheUula pulcheUa, 

 Lihellula forensis, and Platliemis India. On this earliest date the 

 Argia males were chasing the females and some were flying around 



