42 



KNOWLEDGE 



[Januaky 1, 1890. 



rugs, milts, aud other accumulators of dust and dirt. It 

 is commonly believed that cats and dogs bring fleas into a 

 house, and there is certainly good evidence that at least 

 their own parasites may be introduced in this way. For 

 example, Mr. S. J. Mclntire states that, wisliing to obtain 

 some eggs of the cat's flea, he placed, late one night, a 

 cloth for his cat to lie upon, and early in the morning 

 inspected it in order to collect any eggs that might have 

 been deposited. On the first night, 02 eggs were obtained, 

 on the second 78, on the third 67, and on the fourth 77, a 

 total of 28i eggs fi'om one cat in the course of fom- 

 nights ! No doubt many of these, if left to themselves, 

 would never have reached maturity ; still the number is 

 sutticieutly startling, and, imless the animal in question 

 was literally swarming with vermui, seems to indicate on 

 the part of the cat's flea a fecundity considerably in excess 

 of what is usually attributed to the human species, which 

 is said to produce only about a dozen at a laying. Of 

 course it by no means foUows that the fleas which would 

 have resulted from these eggs would have been troublesome 

 to the human inhabitants of the house ; in fact, consider- 

 ing the great zoological difl'erence between man and the 

 eat. the presumption would be in the other direction. It 

 has, however, been asserted, that the cat's flea will attack 

 a human host, but, however that may be, it is evident 

 that, to be on the safe side, rooms in which cats and dogs 

 are accustomed to he, should be frequently swept, and that 

 the sweepings should be burnt. 



From the eggs are hatched, not brown, leaping fleas, 

 but whitish, footless, worm-Uke maggots, whose bodies are 

 set with long hairs (Fig. 5). Each larva consists of a 



Fn;. 5. — Lakva df C'at's Flea (PuIc.t fclis}. (After Kiinckel. ) 



head and twelve segments, the last terminated by a pair 

 of hooks. The head carries four tubercles, a pan- of short 

 antenufe, and a good pair of biting jaws (Fig. 6), for at 

 this period of its life the young flea devours sohd food ; it 

 is neither parasitic nor a 

 blood-sucker. These little 

 grubs are extremely hvely 

 creatures, wriggling about 

 vigorously, aud working 

 themselves along by aid of 

 their hairs and caudal hooks. 

 They appear to feed upon dry 

 animal substances of various 

 kinds, some fi'agments of 

 which they are pretty siu-e to find in the neighbom-hood of 

 their bu-th-place. At the end of the 17th century, Leeu- 

 wenhoek, to whom we owe some of the earliest recorded 

 observations on fleas, kept a colony of larvie, and fed them 

 on the bodies of dead flies. About 50 years later, Eosel tried 

 sjme larv^e with various substances, and foimd that thev 

 refused sawdust, both from old and fresh wood ; and that 

 so far fi-om enjoymg fi-esh blood, they became di-owned in 

 it when small quantities that had been extracted from a 

 pigeon were offered them. He foimd, on the other hand, 

 that they fed readily on the bodies of gnats, and on dried 

 and pulverised blood, and these observations have since 

 been confirmed by other observers. Bearing these facts 



Fig. 6.— Biting Ja« 

 Flea's Maggot. 



in mind, then, it is evident that, quite apart from the para- 

 sites of our domestic qiuidrupeds themselves, rugs, mats, 

 or carpets, on which such animals lie, are hkely, by the 

 accumulation there of hairs, fragments of skin, &c., to con- 

 stitute an environment eminently adapted to the propaga- 

 tion of human fleas, the larvte of which would find there 

 excellent pasturage. In this connection may be quoted an 

 experience of Prof. Westwood, who discovered some larvip 

 in a very unexpected way. He says that, ha\ing dropped 

 a very minute insect on the floor of his library, close to 

 the spot where one of his spaniels was in the habit of 

 lying, he was obliged, in order to find it, to sweep the 

 carpet very carefully with a fine brush upon a piece of 

 white paper. By so doing he found the insect he was in 

 search of, and at the same time swept up what he was 

 ccrtauily not looking for, some smaU hairy, wriggling 

 maggots, which he at once recognised as flea larvie. From 

 what he subsequently states, the Professor seems to imply 

 that these were the larv;e, not of the canine species, but of 

 the human flea. The frequent use of the broom, there- 

 fore, wherever cats and dogs habitually take up their 

 quarters, is eminently desirable, and not the dustbui, but 

 the fire, should be the final destination of all rubbish so 

 swept up. It is obvious, also, that the frequent sweeping 

 out and cleansing of kennels, especially at the edges and 

 in the corners of the floor, would be helpful as a preventive 

 measure towards ridding dogs of fleas. 



In the form of its larva, the flea is in complete agree- 

 ment with the order Diptera, the footless, jaw'-bearing 

 maggot being the usual type amongst flies. 



The yoimg flea does not enjoy a long larval Ufe ; in 

 summer it becomes full-grown in about twelve days, and 

 then spins a little cocoon wherein to become a pupa. 

 Tills habit is apparently sometimes departed fi'om, for 

 Eosel records that some of his larv.e puimted without a 

 cocoon. The cocoon is, of com'se, extremely minute, and 

 to the silken threads of which it is composed are usually 

 attached particles of dust or cotton or woollen fibre, 

 whereby its identity is almost completely obscured. Inside 

 the snug httle abode the tiny maggot divests itself of its 

 larval skin, and appears as an odd, humpbacked chrysalis 

 (Fig. 7). In this the maggot shape has altogether dis- 

 appeared, and the outline of the perfect form becomes 

 evident. Legs for the first time appear, but they are quite 

 useless, as, in common with 

 the rest of the insect, they 

 are encased in a thin invest- 

 ing peUicle, each leg being 

 enclosed in a case of its ow-n. 

 In the character of its pupa 

 the flea resembles the Hy- 

 menoptera (Ants, Bees, Wasps, 

 &c.), and differs markedly 

 from the generaUty of the 

 Diptera. 



The developing flea remains in the condition of a pupa 

 about a fortnight, of course taking no food during this 

 time ; it is at first dirty white, but soon darkens and 

 assumes the well-known yellowish brown tint of the adult. 

 From this pupa issues the perfect flea, and then, for the 

 first time in its hfe, the spirit of bloodthirstiness comes 

 upon it ; never hitherto have its mouth-organs been 

 adapted for taking liquid food, but now it is furnished with 

 the extraordmary collection of lancets referred to in our 

 former paper, and would find it equally difficult to partake 

 of sohd aliment. Those larvae which hatch fi'om eggs laid 

 towards the beginning of winter do not pass through their 

 metamorphoses so quickly, but spend the winter in the 

 larval state, remaining in a torpid condition till the warmer 



Fig. 7. — Popa of Flea. 

 (After Westwood.) 



