INSECTS INHABITING GREAT SALT LAKE AND OTHER SALINE 

 OR ALKALINE LAKES IN THE WEST. 



By a. S. Pack^ied, Jr., M. D. 



The subject of brine-intiabiting insects is one of very considerable 

 interest, both in a physiological tiud zoo-geographical, point of view, as 

 well as fTom its bearings on questions relating to the earlier geological 

 history of the American continent. 



Professor A. E. Verrill has found the larvae of Ghironomus oceanicus, 

 Pack., living at the enormous depth of 120 feet in the sea at Eastport, 

 Maine. We have also found the same insect between tide-marks, in 

 Maine and Massachusetts, and have, in company with Professors Moebius 

 and Kupffer, dredged a very similar species at the depth of three or four 

 fathoms, in the bay of Kiel, on the shores of the Baltic S@a. Thus an 

 air-breathing insect, whose congeners live in fresh-water pools, is capa- 

 ble of living at considerable depth in the sea 



Kow, exceedingly few insects which pass their life in fresh water are 

 found living in the sea; on the other hand, we know of many more 

 marine genera of shrimps, &c., (Crustacea,) which live in fresh water; 

 such are species of Palsemon and allies, and Gammarus ; several species 

 of the former genus are found living in bodies of fresh water, both in 

 the Southern States and in Italy. All the fresh-water forms of life have 

 probably come from salt-water ancestors, as, in the early geological ages 

 there were no large bodies of fresh-water; and as in the present day, 

 both in the great lakes of America (Lakes Superior and Michigan) and 

 the deep lakes of Sweden, which were formerly arms of the sea, we find 

 marine Crustacea in the water, at the bottom, while the surface-water 

 contains fresh- water forms. 



As extremely interesting in this connection, I will translate, from an 

 able memoir of Professor F. Plateau,* some conclusions from his ex- 

 tended studies of the action of the sea on fresh- water insects and Crus- 

 tacea, and of fresh water on marine Crustacea. 



ARTICULATES LIVING IN FRESH WATER. 



1. Sea-water has but a very feeble influence, or none, on aquatic Col' 

 eoptera (beetles) or Hemiptera, (bugs,) in the perfect state; this influ- 

 ence is perhaps a little greater for the larvas. 



2. Sea- water injures such fresh- water articulates as have a thin skin, 

 or branchise, and these effects are, in general, the more marked as the 

 extent of the thin skin is greater. 



3. The fresh-water articulates which can live with impunity in sea- 

 water, are those in which there is no absorption of salt water by the 

 skin; those which die in a comparatively short time, have absorbed 

 chloride of sodium and magnesium. 



4. The injurious salts contained in sea water, are the chlorides of so- 

 dium and of magnesium ; the influence of sulphates may be regarded as 

 nothing. 



5. The difference in density which exists between fresh and salt water 

 does not explain the death of fresh-water articulates in salt water. 



» „ 



• Eecher^hes Physico-Chemiques sur les Articul6'? Aquatiques. Bruxelles, 1870. 



