184 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



The work had not progressed far until it was found impossible, owing 

 to the wide range of temperature, to rear these insects under field 

 insectary conditions. In summer, it was not unusual for the tempera- 

 ture to reach 100° or more and during the winter it fell to 20° below 

 zero. Since these extremes were far in excess of those that would be 

 encountered under natural conditions, they resulted in a high mortality. 

 Inasmuch as it was desired to observe the insects during the winter, it 

 was not feasible to place the insects under compost heaps during this 

 period. 



Another objection to placing the salve boxes under piles of compost 

 is the difficulty in knowing just how much moisture is needed in the 

 boxes. The writer has also found that unless exceptional care is taken 

 the soil and food will mould in the course of three or four weeks and 

 make the boxes untenantable. With these objections in mind, it was 

 decided to try carrying the material through in a cave where the tem- 

 perature could be kept above freezing and where the boxes could be 

 examined at regular intervals. 



In the fall of 1915, a temporary cave was constructed for this purpose. 

 A hole three by five feet was dug six feet in the ground and the sides 

 boarded up sufficiently to prevent caving in. A board roof was placed 

 over the hole about five feet from the bottom and was covered with a 

 foot and a half of dirt. A manhole opening was left in one corner for 

 admittance. This opening was closed with a heavy door covered over 

 with a few layers of burlap. The bulb of a soil thermograph was 

 placed in the cave. The instrument itself was inclosed in a small box 

 on the outside so that the temperature could be determined without 

 opening the cave. A set of maximum and minimum thermometers 

 were also kept in the cave as a check on the thprmograph. With the 

 approach of cold weather early in October, about twenty species of 

 insects were placed in the cave and kept under observation during the 

 winter. Every two or three weeks all the boxes were gone over, the 

 soil changed, and fresh food supplied. Table I gives a list of the in- 

 sects successfully carried through the winter. 



All of the insects appeared to thrive under these conditions during 

 the winter and the mortality was very low. The writer has been at- 

 tempting to carry corn ear-worm pupse through the winter for several 

 years, but always with negative results because the mortality would 

 be from 75 to 100 per cent. With the material kept in the cave, less 

 than 25 per cent died. The behavior of many of the insects kept in 

 the cave was checked with field observations to determine what varia- 

 tions, if any, occurred. Corn ear-worm larvae, placed in the cave early 

 in October, pupated at the same time as did those in a check kept in the 

 field insectary. In the spring, the adults emerged during June which 



