52 ON PLANTS AND INSECTS. [LECT. 



think I cannot do better than select the larvae of the 

 Sphingidce, which have just been the subject of a masterly 

 monograph by Dr. Weissmann, from whom most of the 

 following facts are taken. 



The caterpillars of this group are very different in 

 color green, white, yellow, brown, sometimes even 

 gaudy, varied with spots, patches, streaks, and lines. 

 Now, are these differences merely casual and accidental, 

 or have they a meaning and a purpose ? In many, 

 perhaps in most cases, the markings serve for the 

 purpose of concealment. When, indeed, we see cater- 

 pillars represented on a white sheet of paper, or if we 

 put them on a plain table, and focus the eye on them, 

 the colors and markings would seem, if possible, to 

 render them even more conspicuous ; as, for instance, in 

 D. galii ; but amongst the intricate lines and varied 

 colors of foliage and flowers, and if the insect be a little 

 out of focus, the effect is very different. 



Let us begin with the Chcerocampa elpenor } the 

 elephant hawk-moth. The caterpillars, as represented 

 in most entomological works, are of two varieties, most 

 of them brown (Fig. 43), but some green. Both have 



FIG. 37. Chcerocampa elpenor. First 



a white line on the three first segments ; two remarkable 

 eye-like spots on the fourth and fifth, and a very faint 

 median line ; and are rather more than four inches long. 

 I will direct your attention specially, for the moment, to 



