370 Annals Entomological Society oj America [Vol. X, 



segments are paired bristles, rising from tubercles, and on all 

 the segments except the first there is, under the first of these 

 bristles, another stout bristle on all the segments except the 

 ninth where it is reduced in size and comes under the posterior 

 bristle of the two, on the ventral surface. On the ventral 

 surface each segment bears three rows of ambulacral hooks 

 except the ninth which has none, and the eighth which has two 

 complete rows, the first row broad and entire, the second short, 

 interrupted at middle, the third entire and forked at each end. 

 The ninth segment has the anal region developed into a pseudo- 

 pod. Spiracles biforian, on the mesothoracic, and all abdominal 

 segments except the ninth. Legs composed of a cylindri- 

 cal coxa, which * bears two bristles on its inner margin, a 

 trochanter, cylindrical, short, a femur three times as long as 

 the trochanter, a tibia two-thirds the length of the former and 

 a claw; the claw bears a short accessory spine (visible only at 

 high magnifications). 



I am unable to see under the highest magnification the 

 rudimentary tarsus which Schiodte (18G4) figures. The spine 

 on the claw resembles the figure given by Schiodte for Platysoma 

 depress um. These larvae have great difficulty in crawling 

 unless they can bring the dorsum into contact with something. 

 The hooks, which in the description I called "ambulacral," 

 are used by the larva to push itself along. The larva, in 

 moving, draws up the anal pseudopod and places it; then the 

 segments move forward in rhythmical order, the hooks serving 

 to attach each segment while the next one in front of it is 

 moving forward. The larvce are very voracious carnivores, 

 living on the larvae of an anthomyid fly, and an ortalid fly, 

 eating from six to fifteen a day. 



When the larva is full grown it sets itself to work to make 

 the pupal cell, travelling as much as an inch for material, 

 shredded wood, cotton, filter paper, anything available which 

 it can chew up; the natural material is finely chewed wood. 

 The wood i^ cemented together with an anal secretion, and 

 it is not uncommon to see the larva reach to its anus with its 

 head and apply the secretion gathered to the wall of its cell. 

 I believe that the clypeus and frons are used for carrying the 

 secretion and the clypeus and mandibles used as trowels to 

 spread it. The larva begins by forming a ridge of transported 

 material, then adds to the cell by adding pieces to each side 



