1910] A Structural Study of Some Caterpillars 95 



were mounted in Farrant's gum-glycerine. The same method 

 was tried on formaldehyde specimens, but with much less success, 

 as the muscle would not dissolve easily and had to be picked out 

 piecemeal. 



The remainder of the specimens were examined entire, as 

 opaque objects. By placing them in full sunlight, or even con- 

 centrating it on them with a lens, they could be examined suc- 

 cessfully, even with rather high powers of the microscope. A 

 binocular microscope was very useful, especially in getting a cor- 

 rect idea of the relations of parts, in dissecting, and in hunting 

 for setae. 



Inflations of the smaller species were sometimes immersed 

 in xylol, or in absolute alcohol, when they could be examined by 

 transmitted light. They did not collapse on being taken out and 

 dried again. 



Most of the drawings were sketched with the camera lucida, 

 the details being put in free-hand under a higher power. They 

 were not drawn to a single scale, as they differ a great deal in 

 size, and the size is of little classificatory value. 



The purchased specimens were received with names. In the 

 case of the others, which were named by the writer, there was 

 often some uncertainty, as indicated by question marks in the 

 text. This was especially the case in the Noctuidae and Geome- 

 tridae, where I have listed less than half of my specimens. 



^1^ %i^ ^^ ^^ ^^ «i^ ^1^ ^1^ 



'I* 'J* "T"" "T^ T* •T* ^^ 'l^ 



I wish to express my thanks to the many who have made this 

 study possible by their help in supplying specimens, in allowing 

 the use of instruments and books and by advice and information. 



Wm. T. M. Forbes. 



STRUCTURE. 



A caterpillar is an insect larva in which the thorax and abdo- 

 men are similar in general appearance, the head alone is heavily 

 chitinized; there is no sclerite between the antennae and the 

 mandibles; the mouthparts are small and largely retractile, with 

 lacinia not recognizeable as such and no glossse or paraglossae. 

 The whole structure of the maxillse and labium is peculiar and 

 not closely paralleled in other orders. 



Most of the head as seen from in front, is composed of the 

 two epicrania (compare Fig. 1), each of which usually bears eleven 

 primary setae and the eyes. There are also almost always 



