LARVA OF PRIVET HAWK MOTH. 151 



are even, and the series of somites follow one another without any abrupt change 

 of shape. Such a larva is seen, more or less adapted of course, in most Ametabola 

 and Hemimetabola. The condition of the adult insect is acquired in a graduated 

 series of moults, whilst organs such as wings make their appearance ; and others, e.g. 

 the genitalia, are brought to maturity. It is also seen in some Metabola, as in certain 

 families of Coleoptera, e.g. Cicindilidae, Dytiscidae, &c. ; in some Neuroptera, e.g. 

 Sialidae ; some Megaloptera. In these instances it is occasionally highly specialised, 

 e.g. in the Ant-lion. It appears in others as a. first larval form, subsequently modi- 

 fied in accordance with a change of habit in the direction of the cruciform type, 

 constituting what is known as Hypermetamorphosis. Such a change occurs in 

 Mantissa among Panorpatae, in the Strepsiptera, and in various Meloidae among 

 Coleoptera, e. g. Meloe, Sitaris, Hornia, Epicauta, Cantharis. In Mantispa the second 

 larval form is only sub-eruciform : in the Meloidae there is a number of forms one 

 after the other more and more degraded. (See Packard, American Naturalist, vii. 

 1883, pp. 938-944; Riley, op. id. xii. 1878, pp. 213, 282.) 



The cruciform type of larva is very generally found among Metabola. It may 

 succeed, as just mentioned, a Campodeiform larva, and in its simplest shape, e.g. in 

 Trichoptera, which may be termed sub-eruciform, it is little more than a persistent 

 embryonic form such as is observable in the earliest stages of most Insecta. The 

 caterpillar Qtti\o.Lepidoptera, of the Panorpatae, of Tenthredinidae amongHymenoptera, 

 and the grubs of some Coleoptera are typical examples of the type. The head is 

 well-defined, but the somites of the body are simple and cylindrical (homono- 

 mous), and the animal has a vermiform aspect. Nevertheless a thoracic region 

 with articulated limbs is distinguishable, and what is more the abdomen (except in 

 Coleopterous forms) possesses functional abdominal limbs. Such limbs, but not 

 functional, exist in Thysanura, and as rudiments in the embryoes of most Insecta, 

 e.g. in Hydrophilus (Dytiscidae], which has a modified Campodeiform larva. The 

 limbless grub of Aculeate Hymenoptera, and still more the maggot of Diptera, must 

 be regarded as degenerate examples of this type : and where limbs are present in 

 a Dipterous larva they are probably secondary and special developments. The 

 larvae of all existing Insecta, and even the primitive Ametabolous order Thysanura 

 have been modified to a greater or less extent by Natural Selection. The embryo 

 however has a type of structure which is readily modified in the direction of one of 

 the two larval types ; and it is not surprising to find larval forms, such as those of 

 Trichoptera, which may be regarded as actually transitional between the two. 



Larvae of British Lepidoptera and their Food plants, Wilson, London, 1880. 

 Figures in Horsefield and Moore, Catalogue of Lepidopterous Insects in East 

 India House Museum, 2 vols., 1858-59, and in Dewitz, Jugendstadien exot. Lepi- 

 doptera, Nova Acta, 44, 1883. Aquatic Lepidopterous larvae. Miiller-Blumenau, 

 A. N. 50, 1884; Maurice, Bull. Scientifiques du De'partement du Nord, iv. 



Anatomy. Cossus, Lyonet, Traite' anatomique de la Chenille qui ronge le bois 

 du Saule, Hague, 1762. Sphinx, Newport (and also as to pupa and imago) 

 'Insecta'; Encyclopaedia of Anat. and Phys. ii., London, 1836-39. 



Skin glands. Klemensiewics, Verhandl. K. K., zool. bot. Gesellschaft, Wien, 

 xxxii. 1883. Glandular hairs. Dimmock, Psyche, iv. 1885. 



Muscles. Lubbock, on Pygaera bucephala. Tr. L. S. xxii. 1859. 



Stigmata. Krancher, Z. W. Z. xxxv. 1881. 



