358 Phylum Arthropoda 



an even support for a loose lid, best made with a loop of heavy wire 

 covered by some open-meshed cloth. If need be the lid may be weighted 

 to keep a tight contact with the cylinder. Such a cage is easily and 

 quickly prepared at a low cost, gives perfect ventilation, and affords 

 the maximum facility for cleaning and reprovisioning. If several cages 

 are to be used the diameters should be in a graded series so that 

 the cages will telescope one inside the other for storage until again 

 needed. 



A few items of the utmost importance in rearing the larvae should be 

 noted. Food should be furnished either by growing plants, or by twigs 

 kept fresh in jars or bottles of water. In the latter case the water sur- 

 face must be blocked off or the larvae will drown themselves. Most 

 food plants will not support their full quota of leaves on twigs kept in 

 water. If possible choose a species of plant that keeps well when cut. 

 For T. polyphemus basswood, hazel, dogwood, and birch are especially 

 good. In any case, always reduce the leaf surface to one-half or one- 

 third the normal. The leaves also keep better if washed or dipped in 

 water. This procedure removes dirt and supplies the larvae with a cer- 

 tain amount of drinking water comparable to that available in nature in 

 the form of dew and rain. That water is important for their best de- 

 velopment is evident from the greed with which they drink when the 

 above precaution has been neglected. On one occasion the writer ob- 

 served the drinking of 25 drops of water in succession by a large T. poly- 

 phemus larva that had been reared without drinking water. 



All twigs, whether their leaves are largely consumed or not, should 

 be discarded on the second day, or at the latest on the third day, and 

 the larvae transferred to fresh foliage. This procedure is a fundamental 

 factor in avoiding diseases among the larvae. The only other factors of 

 parallel importance are proper ventilation of the cages, and the imme- 

 diate destruction of all abnormal larvae. The transfer of larvae to fresh 

 food may be quickly accomplished by closely trimming the leaves or 

 stems upon which they are clinging with the scissors, and laying them 

 on the new leaves. This procedure is necessary because the larvae will 

 not move from the old twigs to fresh ones promptly of their own accord, 

 and may not be transferred forcibly without injury. 



As the larvae come to maturity their droppings become large and moist. 

 Finally a large amount of partially digested food and fluid is evacuated. 

 Immediately after this the larvae seek a place to spin their cocoons. The 

 great majority will begin to spin upon the food plant. As soon as well 

 settled they should be removed from the cage and the leaves and twigs 

 supporting the cocoon pinned to the margin of the lid covering the cage. 

 It is important to keep the emergence end of the cocoon upward until 

 spinning is complete — about 2 or 3 days. Otherwise the structure of the 



