June 26, 1885.] 



SCIENCE 



519 



tional facts in natural history always provoke 

 scepticism, and the facts recorded regarding 

 our cicada's hypogean life have shared in this 

 tendenc}'. Hence a few facts, especially such 

 as bear on the development of the larva, will 

 not prove uninteresting. 



Of the tredecim brood which appeared in 

 1868, I have taken pains to follow the larval 

 development as far as possible from year to 

 year, my observations having been made in St. 

 Louis county, Mo. Repeated efforts to rear the 

 young larvae in confinement proved unsuccess- 

 ful ; and it was necessary to resort to careful 

 and repeated digging out-doors in order to 

 watch the growth from year to }'ear. One of 

 my emplo3'ees at Cadet, Mo., has also been in- 

 structed to carefully pursue the same subject, 

 and I have repeated the digging since residing 

 in Washington. These observations have in 

 all cases been made in special localities where 

 the date of entering the ground was well known 

 and observed. I have thus been able to follow 

 the larvae for the first six years with great 

 care, and for subsequent years with less care 

 and continuity. As we might expect from the 

 chronological history of the species, the devel- 

 opment of the larva is extremely slow ; and at 

 six years old it has hardly attained one-fourth 

 of its full size. Notwithstanding this slow 

 development, moulting takes place frequently ; 

 i.e., the number of larval stages is more than 

 one per annum, and probably twenty-five or 

 thirt}- in all, whereas in the Homoptera gen- 

 erally — the suborder to which Cicada belongs 

 — it ranges from two to four. In any Irvpo- 

 gean insect which continually uses its claws in 

 burrowing, the need of shedding and renewal 

 of those organs is apparent, and may afford 

 the chief explanation of this repeated exuvia- 

 tion, though the slow development is a factor ; 

 since mv own experience has shown, in the 

 larvae of other orders, that, in proportion as 

 development is slow, exuviation is frequent. 

 As the claws of the front tibiae are the chief in- 

 struments used in burrowing, the tarsi become 

 useless or obstructive, and are gradually re- 

 duced, and finall}' lost. They are then regained 

 suddenly during one of the later moults, but so 

 articulated that the}- are thrown back on the 

 inside of the tibiae, and form a good brace for 

 strengthening these. They are thus out of the 

 way for underground work, and come into use, 

 with their well-preserved claws, only when the 

 pupa issues from the ground, and ascends for 

 the final change. 



Much difference of opinion has been ex- 

 pressed by different writers as to the food of 

 the larva ; and this is not to be wondered at, 



from the fact that there is great difficulty in 

 observing it feed. Dr. G-. B. Smith insisted 

 that it obtained its nourishment from the 

 moisture of the earth, through capillary hairs 

 at the tip of the proboscis ; while mam- others 

 have seen it with its beak inserted in the roots 

 of trees, and pumping the sap therefrom. The 

 former method is insisted on by Dr. Smith 

 from his own observations ; but while I think 

 it not improbable, especially during its earlier 

 larval life, that the cicada may feed on earth- 

 exudation, — a belief which receives support 

 from the well-known fact that this cicada will 

 issue from ground that has been cleared of 

 timber and cultivated for nearly seventeen 

 years, and that other species are known to 

 issue from the prairies, — the liquid is evidently 

 pumped up in the ordinary way. The truth of 

 the matter seems to be that the cicada larva 

 can and does go for long periods without nour- 

 ishment, where such fasting is necessitated ; 

 and that in the earlier years of its development, 

 more particularly, it feeds on the rootlets or 

 radicles, not only of trees, but of herbaceous 

 plants. In my own observations I have rarely 

 found it more than two feet below the surface 

 during the first six or seven years of its life, 

 and almost invariably in an oval cell, and more 

 often away from roots than near them ; yet I 

 have also found it with beak inserted, and it 

 will often hang fast by the beak after being 

 unearthed. That the larva is capable of going 

 to great depths is well attested by observers. 

 Many of such reports may be based on the 

 unobserved tumbling of the larva from higher 

 levels ; but, where the insect has been observed 

 to issue from the bottoms of cellars ten feet 

 deep, the information would certainly seem to 

 be reliable. 



The method of burrowing and making its 

 cells is quite interesting. With the strong 

 front tibial claws it scratches away the walls 

 of its cell just as one would do with a pick ; 

 and if it is rising, so that the earth removed 

 naturally falls to the posterior end of the bur- 

 row, it simply presses the detached portions 

 on all sides, and especially on the end of the 

 cavity, by means of its abdomen and middle 

 and hind legs. If, however, it is burrowing 

 downward, and the loose soil has to be pressed 

 against the top of the cavity, it uses its broad 

 front femora very dexterously in making a 

 little pellet of the soil, and in placing it on the 

 clypeal or front part of the head, when the 

 load is carried up, and pressed against the top 

 of the cavity. The motions made in cleaning 

 its fore-arms remind one very forcibly of those 

 made by a cat in cleaning its face. The femora 



