The flea / by Harold Russell.

  • Harold Russell
Date:
1913
Catalogue details

Licence: In copyright

Credit: The flea / by Harold Russell. Source: Wellcome Collection.

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    can be no doubt that many undiscovered species still remain, and will now, in due course, be collected, described and named. The position which should be assigned to the order Siphonaptera in the general scheme of insect classification is a question on which the most learned modern entomologists have disputed with considerable vigour. Some see the nearest relatives among the beetles, others among the flies. The majority, as we shall see later on, would place them near the Diptera: but since no convincing arguments have been pro- duced on either side it may be wisest to regard the question as still at present unsolved. Fleas belong to one of the groups of insects which go through a complete metamorphosis. Their life- history consequently falls into four divisions: egg, larva, pupa and imago. If the climate permits, the female flea lays her eggs all the year round, and from one to five are dropped at a time. Unlike those of many other parasites they are never attached to the hairs of the hosts, but appear to be deposited indis- criminately on the floors of houses or in the nests and sleeping places of their hosts. The eggs generally hatch in a few days, and a minute, white, wormlike larva emerges (Fig. 1). The W of some, and possibly of all, fleas are provided with a wonderful adaptation m the shape of an egg-breaker or hatching-spine. This IS a thin plate, like the edge of a knife, where
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