230 



THE AMERICAN 



sides. Under lip and mentum are represented 

 by a horuy, projecting-, sliglitly emargiuate and 

 tridentate piece, behind wMcli there is another 

 piece, fringed with numerous liairs, especially 

 on the sides. The body of the larva is smooth, 

 of a dirty greenish-gray, this appearance being 

 produced by numerous spots of tliis color on a 

 pale ground. On the underside of the thoracic 

 portion there is a subcorneal, retractile process, 

 crowned with a circular row of bristles. If 

 examined with a lens, this organ appears to 

 consist of a system of parallel black lines ; but 

 if a much stronger magnifjang power is used, 

 these lines prove to be dense rows of short, sharp 

 bristles. The joints of the body are not distinct ; 

 stUl I could count twelve joints, five of wMch 

 formed the club-shaped anal portion of the body, 

 the four or five joints immediately preceding 

 them are more apparent than the others. The 

 anal extremity consists of a subcylindrical, trun- 

 cated protuberance, crowned with rows of bris- 

 tles, similar to those of the thoracic proleg. 

 Immediately below it, on the underside of the 

 body, there are thi-ee (Fries mentions only two) 

 short, cylindrical, soft, cuiwed, retractile tenta- 

 cles, to which the lai'ge tracheiB lead. These are 

 probably the organs of respiration. I did not 

 discover any traces of stigmata, nor does any 

 other author mention them. 



The strange fan-shaped organs are apparently 

 used for procuring food. Under a strong mag- 

 nifying power, each CFig. la.z 

 of the scythe-shaped ^^ ^ 

 rays which compose 

 it appears lined on the 

 inside with exceed- 

 ingly minute hairs, 

 the fringe of which 

 is interrupted at 



regular intervals by S- «? ce^ 



1 , . , „. Explanation of Figube 147 — 



short, conical projec- ,a) portion of a ray of the fan; 

 tinno Tlimjo nlrpnrlv (*) mandible; (c) maxilla; (d) 



tions. iliaveaueacij ;,„;t,eriip; (e/npperiip-aii en- 

 remarked above, that larged —Afttr Osten Sacken. 

 the twit on the mandibles consists, if I have 

 seen right, of a row of small rays of a consist- 

 ency similar to those forming the fan ; it is prob- 

 able that this tuft is used for cleaning the fan 

 when it is closed and turned with its tip towards 

 the mandible. The fan is usually spread out, 

 but I have noticed that sometime before assum- 

 ing the piipa state, the larva keeps it constantly 

 closed, evidently because, at this period of its 

 life, it ceases to feed. 



What the homology of these organs is, I am 

 not able to suggest. They seem to be absolutely 

 supernumerary, as the mouth, without them, is 

 complete, that is, contains all the parts of a 



typical insect mouth. This is an interesting 

 question, worthy of being inquired into. As to 

 the use of these fans, it is undoubtedly for catch- 

 ing the animalcules which constitute the food of 

 the lai-va ; but what those animalcules are, again 

 we do not know, and have not been able to in- 

 vestigate. The vagaie statement of Planchon, 

 that in the stomach of one of the larvas he found 

 a prodigious quantity of round or elliptical ani- 

 malcules, some dead, some still alive, cannot 

 satisfy us. 



The larvfB are sometimes seen swimming by' 

 means of a jerldng motion. They can also walk, 

 by doubling their body and using alternately 

 their anterior proleg and their anal protuber- 

 ance. 



According to Verdat, the larva moults more 

 than once. When full grown and about to un- 

 dergo its transformation, it spins an obconical, 

 graj-ish, semitransparent pouch, fastened to a 

 plant or a stone ; in this XDOuch the pupa is in- 

 serted, its anterior end protruding above the 

 upper rim. I have seen the process of spinning. 

 The larva does not leave its foothold but re- 

 mains in the centre of its work, using its 

 mouth, from which the filament is drawn, and 

 helping with its proleg. (According to an ob- 

 servation communicated bj"^ Audouin to West- 

 wood, the cocoon is first formed entire, closely 

 resembling one-half of a diminutive egg, cut lon- 

 gitudinally, and fastened by the flat sui-face to 

 the leaf or stone ; subsequently, the upper end 

 is eaten away as far as a thickened arch, pre- 

 viously formed. As I have happened to come 

 across this remark long after I made my obser- 

 vations, I am not able either to confirm or to 

 reject it.) According to Planchon, the skin is 

 not cast by the larva, but seems to dissolve and 

 thus gradually to disclose the outlines of the 

 pupa. (According to another author, the head 

 alone is thrown off.) 



The pujoa, on each side of its thorax, has a tuft 

 of filaments, serving evidently for respiration. 

 From a common root I saw eight principal 

 branches proceed, which, at some distance, split 

 in two, thus forming' sixteen filaments. (Fries 

 mentions and figures only four filaments on each 

 side; Fabricius, six; Verdat's and Scheffers'. 

 larvae had eight. I do not know how to account 

 for these ditt'erences.) Verdat mentions " a 

 cylindrical body, at the basis of these tufts, 

 appearing scaly at its root and conical, spongy 

 at the tip." I did not see anything of the kind. 

 On the abdomen of the pupa, I perceived, along 

 the posterior margins of the 3d and the 4th dor- 

 sal segments, rows of eight very minute spines ; 

 they are arranged in gxoups of four, separated 



