602 TEXT-BOOK OF ENTOMOLOGY 



b. The cruciform type of larva 



Brauer also sagaciously pointed out that "a larger part of the 

 most highly developed insects assume another larva form, which 

 appears not only as a later acquisition, through adaptation to cer- 

 tain definite conditions, but also arises as such before our eyes. 

 The larvae of Lepidoptera, of saw-flies, and Panorpidse show the 

 form most distinctly, and I call this the caterpillar form 

 (Raupenform). That this is not the primitive form, but one later 

 acquired, we see illustrated in certain beetles. The larvae of Meloe 

 and of Sitaris, in their fully grown conditions, possess the cater- 

 pillar form, but the new-born larvae of these genera show the 

 Campodea-form. The last form is lost as soon as the larva begins 

 its parasitic mode of life. . . . The larger part of the beetles, the 

 Neuroptera (in part), the bees and flies (the last with the most 

 degraded maggot form), possess larvae of this second form." In 

 1871 we adopted these views, giving the name cruciform to this type 

 of larvae, and afterwards Lubbock adopted Brauer's views. Brauer 

 considered that the cruciform larva was the result of living a sta- 

 tionary semi-parasitic life on plants, in carrion, or burrowing in the 

 trunks and branches or leaves and buds of trees, where they do not 

 have to move about in search of their food. The change from the 

 Campodea-form to the eruciform larva is a process of degeneration 

 and often of atrophy of the limbs, and, in the footless forms of 

 dipterous and hymenopterous insects, of the gnathites, accompanied 

 by a tendency of the body to become more or less cylindrical. 



The first steps in the origination of the eruciform larva were 

 apparently taken in the order Neuroptera, as restricted by Brauer 

 and by myself, where, though the larvae are campodeoid, there 

 is a true resting pupal stage. The most generalized larval form is 

 perhaps that of the Sialidae (Fig. 560, 1), in which the body tends to be 

 slightly cylindrical, though the legs are long, and the gnathites well 

 developed for seizing and biting their living prey. The terrestrial 

 larvae of the Hemerobiidae, though modifications of the sialid larval 

 form, are considerably specialized in adaptation to their active car- 

 nivorous habits. But the life-history of Mantispa, where there are 

 two larval stages, gives us plainly enough the key to the mode in 

 which the complete metamorphosis was brought about. The larva, 

 born a true Campodea-like form, with large, long, 4-jointed legs, has 



FIG. 561. Coleopterous larvae showing passage from campodeoid to eruciform larva 1 : a, t>, 

 Harpalus ; c, Dyticus ; d, Staphylinus ; e, Silpha ; /, Melanactes ; g, Ludius ; A, Elater ; i, Ponacia ; 

 j. ClirysoDOthris ; k, Orthosoma ; I, Coccinella; m, Byrrhus ; n, Trox ; o, p, Lachnosterna ; </, 

 Labidoinera ; r, Ptlnus ; , Anobiurn ; t, Balaniuus (entirely apodous). 



