A. W. Bacot and W. Gr. Ridewood 
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a larva partially drowned in weak alcohol, but in crawling the action is 
so regular and rhythmical that it is impossible to say whether pro¬ 
gression is due to independent movement of the various setae. 
When the movements are more vigorous, and in travelling over rough 
surfaces, the larva bends down the head, hooking what one may call 
its chin over some relatively fixed object, and then by contraction of 
the longitudinal muscles draws up the rest of the body. The two anal 
processes or struts (“ caudal stylets ” of Packard) on the tenth abdominal 
segment are then turned downward and outward, and gain a purchase 
upon some roughness of the ground ; the body is then elongated, and 
the raised head slides quickly forwards, until it bends down again and 
hooks over some other irregularity in the surroundings. The function 
of the anal processes is thus to prevent any backward slipping when 
the body is in process of elongation and the head stretching forward 
for its next effort. 
The larvae of fleas are of a semi-transparent white colour, with a 
yellow or brownish head, but the colour of the body depends to a large 
extent on the contents of the alimentary canal, and a larva which has 
recently been feeding on particles of dried blood is darker than one which 
is fasting, owing to the reddish or blackish alimentary canal showing 
through the transparent body-wall. 
Even as late as 1868 (cit. Blanchard, 1868, pp. 631-632) Montandon’s 
agreeable fable was credited of the mother-flea leaving its mammalian 
host in order to disgorge into the mouths of its larvae crawling on the 
ground the blood which it had recently sucked. While this story is now 
regarded as a pleasing fancy of the imagination of naturalists of the past, 
it seems nevertheless true that the chief food supply of some (probably 
most) species is the excreta of their parents, and although some larvae 
seem to be able to live on any small dry organic fragments they encounter, 
others, e.g. those of Ceratophyllus fasciatus, cannot be satisfactorily 
reared in captivity unless they are supplied with the excreta of adult 
fleas or particles of dried blood. 
Defrance, as far back as 1824, suggested that the small blackish 
grains found with the eggs and larvae of fleas, and upon which the larvae 
are known to feed, are not, as was previously thought, the faeces of the 
parent fleas, but dried drops of blood which have flowed from the 
■wounds of the host inflicted by the adult fleas after they have sucked 
as much as they required. He based his conclusion on the irregularity 
in the size and shape of the grains and the fact that when moistened 
they resemble dried blood rather than fleas’ excrement. Recent 
