295) yOCTUJD LARVAE— RIPLEY 53 



This subject has been investigated experimentally in order to obtain 

 so far as possible a means of expressing mathematically the relative 

 "subterraneanness" of various species of noctuid larvae. The material 

 used in these experiments was reared under approximately natural condi- 

 tions. Before being submerged in water the larvae were washed to remove 

 all soil and particles of foreign matter such as might carry minute air 

 bubbles beaneath the surface. Immediately after washing, each larva was 

 put in 150 cc. of distilled water five cm. deep contained in a small glass jar. 

 When the larvae were small, two or three were usually put together in the 

 same jar. In order to keep conditions as constant as possible throughout 

 this series of experiments, the jars were kept in a constant temperature 

 chamber at about 17 degrees C, there being occasionally a deviation of one 

 or two degrees in either direction for a few hours at a time. They were 

 exposed to natural light but not to direct sunlight. At the end of the period 

 of submergence the larvae were dried on filter paper, then placed on a 

 blotter six inches below a fifty watt Mazda electric light. Subjected to 

 the stimulation of this irritating factor, manifestations of life could be most 

 readily brought forth. While in this situation, the time required for the 

 individuals to regain various degrees of activity was recorded. They were 

 kept under the light for lengths of time varying from fifteen minutes to 

 three hours or more, depending upon the readiness with which activity was 

 regained. When stimulated as much as possible by this means, the 

 individuals were isolated, each being placed under approximately natural 

 conditions with food, in order that observations on the later effects of sub- 

 mergence might be made for several days. 



The first few seconds of submergence are always spent in violent move- 

 ments of the entire body, after which the larva suddenly becomes motion- 

 less, remaining so until removed from the water. Individuals undergoing 

 ecdysis float, necessitating their being weighted down by a small piece of 

 metal tied to the anal uropods by a fine thread. It seems probable that 

 there may be a layer of air between the old and new cuticle, which would 

 account for the low specific gravity of larvae in this condition. When not 

 molting, they always sink immediately. After being removed from the 

 water, dried, and placed under the light, the first signs of life are usually 

 represented by the beating of the heart, which can be observed according 

 to the transparency of the integument. Slight movements of the antennae 

 and thoracic legs are next to be seen, followed by a feeble curling of the 

 thorax caused by contractions of the longitudinal muscles, often accom- 

 panied by an extension and retraction of the crochets. As various kinds 

 of motion of the trunk and appendages become more marked, water is 

 expelled in quantity from the mouth and anus. When in this stage of 

 recovery, larvae placed with the ventral surface uppermost gradually turn 

 over. Sometime later they will crawl a little when mechanically stimu- 



