Psyche 



[February 



ciable extent from that of the fifty-seven other larvae of the same 

 series in the same trays. Up to the date of writing, September 23, 

 1915, three adults have emerged from this material, all of which 

 appear to be perfectly normal, only seven of the larvae have died 

 and the remainder are moulting normally and feeding freely. In 

 this same type of cage and in the same insectary, we have been 

 carrying on experiments with about 2,000 Elaterid larva* from all 

 partis of the United States and the West Indies. 



However, this is the only instance of prothetely that we have 

 ever observed. The soil with which these cages are filled is all 



Fig. 1. Plotted curve of Meto/to<MS molting periods. Cross indicates point at which pro- 

 thetelous larva appeared. The dotted lines connect actual record points. 



taken from one potting bench. The amount and kind of food, I 

 believe, can be eliminated as a factor in this particular instance as 

 our larvae are always supplied with an excess of food. The lids of 

 the boxes, which we use as cages, fit with varying degrees of tight- 

 ness and the rate of evaporation is, therefore, very inconstant in 

 any given series of cages. On account of this, the cages are only 

 watered when, in the judgment of the examiner, it is necessary. 

 This introduces a large personal factor and could easily result in a 

 cage becoming much more dry or moist than the other cages of the 

 same series. As this seems to be the only variable, 1 am inclined 



