25 
styliform. In the male the mandibles usually present specific 
differences. 
Beneath the mandibles is a projection called the hypostome. 
Sometimes an epistome is present above the mandibles. Projecting 
from either side of the head or capiteUum are the palpi, which are 
provided with sensory organs. 
The mferior surface of the Gamasidse is provided with a varving 
number of chitmous shields or jilastrons, upon which are located the 
genital apertures. The legs are six jointed, being divided mto coxa, 
trochanter, femur, patella, tibia, and the terminal tarsus, provided 
with hooks or sucking disks. The Jemale genital opening is usually 
between the sternal and genital plate. In the male it is m the 
sternal plate. 
The act of coition is very remarkable and has been described m 
detail by Michael.® Briefly, it consists in the deposition by the male 
of a mass of spermatozoa (often contained in a delicate cyst) into the 
spermatheca, a sac comiected with the uterus m the female. The 
spermatozoa upon liberation fertilize, from time to time, the ova as they 
become ripened. Gamasidx lay comparatively large eggs, from which, 
with a few notable exceptions, six-legged larvae are hatched. In the 
genus Lelaps the eggs, when deposited, are fully one-eighth the size of 
the female. One egg only is deposited at a time. It contains a fuUy 
formed embryo with six legs and fully developed nervous and diges- 
tive system. Very soon after expulsion from the female the delicate 
membrane or shell which incloses the embryo is ruptured and a six- 
legged larva appears. After several moultings of the skin the adult 
is formed. The immature mites are termed nymphs and, accordmg 
to the number of moults gone through, protonymphs, deutonymphs, 
tritonymphs, etc. In the nymphal stage many of the Garnasidse are 
migratory. Often they attach themselves to beetles, mosquitoes, 
and other insects, it is believed for the purpose of distribution. 
LIFE HISTORY OF LELAPS ECHIDXIXUS. 
The species of Lelaps {L. echidninus Berlese) found upon white rats 
is a true parasite and sucks the blood of the animal. Its habits differ 
greatly from those of ticks in that its depredations are constantly 
repeated and only a small amount of blood is taken at each feeding. 
The mite is but shghtly distensible, hence its capacity is hmited. 
The foUovdng biological observations have been made in connection 
with the studies on Hepatozoon perniciosum: 
When rats are kept in a cage of some size, in which there is an 
abundance of straw, the mites appear to feed almost exclusively at 
night and during the day they leave the host and live in the damp 
« ^Michael, A. D. : British T 3 voghq)hid 8 e. Ray. Soc. 1, 1901, 291 pp. ; II, 1903, 183 pp. 
