Growth of Plecoptera (stonefly) nymphs at constant, abnormally high temperatures

Six species of Plecoptera were maintained at four different temperatures, which were constant and higher than occurred in the natural habitat, and three species at two different day lengths. Each animal was weighed each day or each week. Weight of two species in the wild was monitored from periodic collection. The weight of each animal fluctuated rhythmically, changing about five percent every five days. These short - term fluctuations probably resulted from changes in water content. Molting occurred when a peak weight was predicted from the cycle and involved temporary gain of about 20 percent in weight. Growth probably stopped for some time before molt and was most rapid just afterward. Many animals died at molt. The time before death was less for univoltine species than for those with longer life cycles. Plecoptera collected in winter from water near 0 C lived for shorter times than did those collected in autumn from water near 10 C. Two species died sooner at higher temperatures and one died sooner with shorter day lengths. Growth in the laboratory was generally slower than in nature. One species grew faster, while three grew more slowly at higher temperatures. One species grew faster under long - than short - day conditions. Premature emergence, expected at the higher temperatures, did not occur, except in one animal.     

Records of stoneflies (Plecoptera) from Nevada

Distributional data are presented for 13 species of Nevada stoneflies including eight species new to the state list. A checklist of 30 species confirmed for Nevada is included.     

New records of stoneflies (Plecoptera) from New Mexico

Distributional data are presented for 30 species of New Mexico Plecoptera including 8 species new to the state list. Previously, many of the included species were known from a single location in the state. A revised checklist of 46 confirmed species is presented for the state.     

Studies on the tolerance of aquatic insects to low oxygen concentrations

Acute, short - term (96 - hour) tests were conducted to determine the relative sensitivity of low oxygen concentrations to 20 species of aquatic insects. In addition, the longer - term effects of low oxygen levels on the survival, molting, growth, and emergence of 21 species were studied. This paper encompasses work conducted at the University of Montana Biological Station from 1968 to 1970 and at the University of Utah from 1966 to 1972. An evaluation of the average minimum dissolved - oxygen requirements of the different groups of aquatic insects tested indicates that the mayflies are the most sensitive, that the stoneflies are next, and that the caddis flies, freshwater shrimp, true flies, and damselflies follow, in that order. While two species of mayfly could tolerate as low a dissolved-oxygen concentration as 3.3 mg/1 for 10 days, a level of 4.6 mg/1 was required for 50-percent survival at 30 days. Fifty percent of the true flies and damselflies tested were able to survive at levels ranging from 2.2 to 2.8 mg/1 for periods ranging from 20 to 92 days.       

The relationship of lateral geniculate activity to the electrocorticogram in the presence or absence of the optic tract input

Zusammenfassung Am Kaninchen wurde die Beziehung zwischen Elektrokortikogramm und Impulsentladungen der Einzelzellen des lateralen Knickes untersucht und die Befunde bei normaler Netzhauttätigkeit mit denen am entkoppelten Auge verglichen. Die reversible Entkoppelung der Netzhaut wurde mit intraokularer Drucksteigerung hervorgerufen. Die Spitzenpotentiale, die schon im Dunkeln gruppiert auftraten, waren im Flimmerlicht reizabhängig. Die Durchschnittsfrequenz dieser Entladungen erwies sich nur wenig vom verwendeten Lichtreiz beeinflussbar. Elektroenzephalographische Weckreaktionen traten sowohl im Dunkeln, als auch im Licht, mit erhöhter Durchschnittsfrequenz der Zellenpotentiale gleichzeitig auf. Bei entkoppeltem Auge wurde während der Weckreaktion eine Erniedrigung der durchschnittlichen Entladungsfrequenz beobachtet. Aus diesen Befunden wird geschlossen, dass der laterale Knick auch von anderen Gebieten aus, nicht nur von der Netzhaut, beeinflusst wird.

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One of us (G. B. A.) held an Alexander Piggot Wernher Memorial Fellowship in Ophthalmology. The research reported in this paper has in part been sponsored by the Office of Scientific Research of the Air Research and Development Command, United States Air Force, through its European Office, under Contract AF 61 (514)-1083.