36 BRITISH LEPIDOPTERA. 



pads can be opened and shut, so that the larva can cling with great 

 tenacity to anything upon which it is resting. Among the moths the 

 arrangement of these hooks appears to follow well-defined, general 

 rules. 



Chapman has discovered that the prolegs of the ordinary external- 

 feeding larvae of the Lepidoptera-Heterocera are essentially of two 

 types, which he calls respectively the " Macro," and the Pyraloid or 

 " Micro " type. The former has a series of hooks on the inner side of 

 the ventral prolegs only, and this appears to be characteristic of 

 exposed-feeding larva (Sphingids, Bombycids, Nolids, Noctuids and 

 Geometrids). The Anthrocerids (Zygaenids), although classed as 

 Incomplete, have prolegs of the " Macro " type. The latter (Micro 

 type) has a complete circle of hooks to the ventral prolegs, and appears 

 to be characteristic of concealed-feeders (Pyralids, Phycids, Crambids, 

 Gelechiids, Plutellids, and (Ecophorids). The most remarkable pro- 

 legs are those of the Eriocephalides. In the larvae of these moths, 

 eight of the abdominal segments bear a pair of minute jointed legs 

 of the same type as the thoracic. 



Chapman thinks that he finds some suggestion of the probable 

 development of prolegs and their hooks in the Adelids — Nematois 

 fasciellus and Adela rufimitrella. In the larvae of these species there 

 are "series of chitinous points beautifully arranged in rows, like the 

 teeth of a shark, the larger in front, those in each row alternating 

 with those in the next rows, and gradually getting smaller, till they 

 merge in the fifth or sixth row, in the ordinary integumental points. 

 In the ordinary position of each proleg there are two sets of points 

 facing each other along a transverse line. In Incurvaria muscalella, 

 the prolegs have two rows of hooks facing each other in this way along 

 a transverse line. In i". (Lampronia) capitella, the young larva has no 

 hooks, but the full-grown larva has hooks placed in a circle, yet with 

 gaps showing that they are still an anterior and posterior set. In 

 the Tortricids, the row of hooks is usually double ; that is, there are 

 longer and shorter hooks, but they are always in one perfect row ; but, 

 in other families, we find that traces of the multiple row of Nematois 

 persists. This is the case in Hepialus. In the Sesiids, again, the 

 circle of hooks is flattened antero-posteriorly, and is weak or wanting at 

 the outer and inner ends, showing a relationship to Incurvaria. The 

 anal prolegs very rarely have more than the anterior half developed. 

 In Hepialus the circle is fairly complete. The Crambids have hooks of 

 alternate size, like the Tortricids. Crambus often has three sizes of 

 hooks alternated in one row." Attention is also drawn to the fact 

 that the larvae of the Hesperids show, in their three rows of hooks, a 

 persistence of Adelid (or, at least, very low) structure, whilst the adult 

 larvae of the true butterflies have the same structure as the true 

 " Macros." 



The same observer finally concludes that "the proleg seems to 

 reach its full development with a complete circle of hooklets. A higher 

 development of the insect is not only accompanied by a fuller deve- 

 lopment of the inner half of this circle, but also by the degeneration 

 and disappearance of the outer half. This may often be followed out 

 in ' Macros,' usually among the butterflies, where the young larva has 

 ' Pyraloid ' prolegs, which often suddenly (at one moult), or more 

 gradually (in two or three), assume, in the full-grown larva, the 



