APHIDiyOEOUS CRABEONIDiE. 165 



nidificate in the bramble, there is no other that I 

 know which makes the like provision." 



Curtis was aware of the Aphidivorus habits of Psen, 

 and figures the insect amongst others.* 



The imago measures 2*5 lines across the wings, and 

 sometimes occurs as early as April. 



It might seem to be a natural inference that the 

 lowest cells in the series being first stored and com- 

 pleted, the occupants would first undergo their 

 changes, and in the act of liberating themselves dis- 

 turb the whole series of cells above them. But it is an 

 ascertained fact that the egg is fixed to the first speci- 

 men of the prey at the bottom of each cell, and that 

 the larva gradually works its way upwards, for its head 

 is always turned in the direction of the exterior opening. 

 After consuming its provision, it eventually hibernates 

 as an adult larva, and does not change into a pupa 

 until the following year, a few weeks after which it 

 assumes the imago condition. A remarkable cir- 

 cumstance has been communicated to me by Sir S. 

 Saunders, that " in the protracted period which inter- 

 venes before the imago is matured, and which may be 

 accelerated or retarded by heat or cold, it matters 

 little whether a month or two more or less should 

 have elapsed." 



Psen constructs its cells in sequence, but does not 

 confine itself to a single row of chambers. Three or 

 more series may run parallel to the length of the 

 stem ; and in the escape of the imago, as might be 

 anticipated, the dividing walls of one series occasion- 

 ally break through to the adjoining empty cells. Such an 

 example may be found in my figure on Plate LXXXV, 

 where twenty cells or more succeed each other in a 

 piece of bramble stem not more than six inches long. 



Sir S. Saunders informs me " in all instances where 

 these cells are constructed in a serial sequence, such 

 as those of Psen, Trypoxijlon, Crahro, and others, the 

 larvse remain with their heads directed towards the 



* Curt., 2nd edit., ' Brit. Ent,,' pt. 25. 



