1918] Marchand — A Thermotropism in Anopheles punctipennis 131 



eter, filled to a depth of about one and one-half inches with water 

 from a pond, more than two hundred Anopheles larvse, mostly 

 collected in a half -grown stage, many of them in very young stages, 

 developed into pupse. The pupse when formed were taken out 

 with a pipette and transferred to another jar with provisions for 

 the adults to hatch. 



In order to rear Anopheles larvae successfully, it is necessary to 

 feed them, and this fact has not been sufficiently emphasized. It 

 was found that certain unicellular surface algse, the species of which 

 could not be determined, form a very satisfactory food. These 

 algae developed freely in one of the glass-covered aquaria in the 

 Vivarium of Princeton University. In this aquarium they covered 

 the whole surface of the water in a continuous green sheet, which 

 was wrinkled and folded in places through the excessive develop- 

 ment of the algae. In order to transfer these to the culture dishes 

 it was sufficient to dip the finger into this stratum and then dip it 

 into the Anopheles-basin; here the algae, upon reaching the clear 

 surface of the water, would immediately spread out over the whole 

 surface in the form of a thin, opaque, green layer. The Anopheles 

 larvae would at once start feeding upon these minute algae, a clear 

 area soon forming around the head and mouthparts of each larva. 

 Before evening, the larvae had cleared the whole surface of algae. 

 The procedure w^as repeated at night in order to provide food for 

 the larvae to last until the next morning, when again the algae had 

 been completely devoured. In this way they were fed regularly 

 twice daily. Under ordinary conditions, when Spirogyra or other 

 filamentous algae are given as food (C. A. Smith), ^ many larvae 

 usually die, because, as a matter of fact, their natural way of feed- 

 ing is at the surface. Howard, Dyar, and Knab (1912)^ suggest 

 that, to provide food the jars in which Anopheles larvae are grown, 

 should be kept uncovered, "in order that the dust from the air may 

 settle continuously upon the water." Undoubtedly, the Ano- 

 pheles larvae may feed on surface bacteria or protozoa, but in 

 absence of green plants, the contamination of the water often causes 

 death. When surface algae are given, as in the case here recorded, 

 practically no larvae are lost, because these algae produce oxygen 



1 Cora A. Smith. The Development of Anopheles punctipennis Say. Psyche, Vol. XXI, p. 1. 



2 Howard, Dyar, and Knab. The Mosquitoes of North and Central America and the West 

 Indies. Vol. I, 1912. 



