662 General Notes. (August, 
Figure 2, a renders a detailed description of the mouth-parts 
A noticeable 
characteristic is the differ- 
ence in size and shape of 
the right and left mandibles. 
The right is longer, more 
slender and strongly 
curved, and has a bicuspid 
prominence on the cutting 
edge. The left one has a 
single minute tooth. The 
maxillz are the most promi- 
Fic. 2.— Head an .. nent mouth parts, and are 
larva, enlarged; a, fsa ade elas aaa Blew: probably chilly useful as 
eenemeapees palpi. They are especially 
large in the youngest larva. The terminal palpial joint and the 
small appendage of the second joint have areas at their apices 
from which arise tactile.rods. The inner edges of the long basal 
joints of both the maxilla and antennz are beset with numerous 
straight hairs. Lateral basal prominences of the labium are 
roughened with minute, depressed, tooth-like processess. 
The legs do not vary perceptibly ; all have the femora supplied 
with fringes of soft hair (Fig. 2, 8). 
The striking feature of the tracheal system is two large longi- 
tudinal trunks, one on each side of the middle line of the 
body (Fig. 3 % dia 
acles are never 
i Fic, pees y racheal system of Hydrophilus larva. - : 
@, bode showing the a branches of tracheal certainly or tru termi 
system; 4, opening of large spiracle; c, terminal besides the large ence 
appendage; d@, stigmatal bran - ie i irs of 
Ret del) 3 @, stigma ch of trache. (Gar- ya] pair, nine pairs 7 
iracles, with bran a 
of these 
running to them from the large trunks, can be counted. One 
