36 SUMMABY OP CURRENT RESEARCHES RELATING TO 



beneficial simplification, the great object being to bring the two 

 maxillfB together ; the latter organs were able to assume a greater 

 development in consequence of the reduction of the former ; this 

 development was further promoted by the abnormal method by which 

 food was obtained. The increase in the length of the tube was caused by 

 the depth which the nectaries of certain flowers exhibited, and by which 

 they excluded insects hurtful to them, while, at the same time, this 

 very depth allowed of the accumulation of a greater amount of honey. 



The transverse striation of the tube, noticed by Reaumur, is 

 produced by semilunar bands of chitin, which are set side by side 

 from the root to the extremity of each half-tube in two series of 

 half-hoops, exterior and interior ; the degree of their development 

 varies in diiferent insects ; they are most slender at the ajiex, a fact 

 which is partly due to the space occupied by certain papilloid pro- 

 cesses on this part. The form of the bands also varies ; in some 

 Lepidoptera they are broken up into a series of separate chitinous 

 pieces ; sometimes, as Gerstfeldt has observed, they are forked, but 

 in this case they are divided only into two arms, not three, as stated 

 by that observer. The transition from the condition in which the 

 bands are composed of series of sej)arate pieces to that in which 

 they form continuous strips is well seen in passing from Pieris to 

 Vanessa, though even in the latter genus (e. g. V. cardui) the trans- 

 verse chitinous series are not wholly united into bands. It is un- 

 certain whether the disconnected or the consolidated form of the 

 chitinous bands of the tube is the primitive condition. The apposed 

 edges of the two halves of the tube may be either serrate (Egyholia) 

 or plain (^Argynnis). 



The apex of the proboscis presents, as already well known, certain 

 organs called juice-borers. The simplest form of these is (1) that of 

 simple hairs, which occur on every proboscis, and consist of a basal 

 chitinous ring, the " cylinder," and a true hair-shaft, which is 

 traversed by a horny mass, the " axial radius," termed " central mass " 

 in the juice-borers ; the cylinder is usually imbedded in the main 

 substance of the tube. When true sap-borers coexist with them, the 

 hairs are short, and vice versa. The varieties in form of the juice- 

 borers are caused by varieties in the peripheral portion of the shaft. 

 2. Juice-borers, with the upper edge of cylinder dentate, e. g. Vanessa. 

 Cylindrical or barrel-shaped, the teeth are six to eight in number, 

 moderately sharp ; in Pyrameis virginiensis they are cylindrical, 

 laterally compressed. 3. Juice-borers with longitudinal ridges formed 

 by the chitinous covering of the " central mass " which spreads out 

 into six plates, running parallel to its axis, e. g. Catocala, Noctua, 

 Plusia, Mamestra, Agrotis, Triplimna, Phlogophora, ' Tceniocampa, 

 Euclidia, &c. 4. Juice-borers of Arge Galathea. Upper surface 

 armed with six teeth, and three similar whorls of teeth in succession 

 below them, parallel to the first series; the points are directed towards 

 the apex of the organ. 5. Unarmed juice-borers ; e. g. those of 

 Argynnis, Melitcea, Ageronia Arete, Macroglossa, Hesperia, Taygetis 

 Xanthippe, Heliconius, Eneides, Agraulis, &c. 6. Juice-borers of 

 Scoliopteryx libatrix. Of two forms, (a) A thick-walled cylinder, 



