NO. 6 



CATERPILLAR AND BUTTERFLY — SNODGRASS 



15 



complex chemical components of the essential oils of the Umbelliferae, 

 which impart a characteristic odor to plants of this family. Caterpillars 

 greedily drink sweet solutions, but give a decisive avoidance reaction 

 to a salt, sour, or bitter solution. Tests on Apamea velata and Mala- 



Mcl 



Fig. 8. — Alimentary canal and head glands of caterpillars. Lettering as on 

 figure 7, except mdGld, mandibular gland. 



A, Tent caterpillar, Malacosoma americanum, crop contracted, stomach full 

 of food, greatly extended. B, Same after a period of feeding, crop extended, 

 stomach contracted. C, Caterpillar of Enarmonia pseudonectis opened from 

 above, showing alimentary canal, silk gland (skGld), and mandibular gland 

 (mdGld) of left side (from Teotia and Pathak, 1957). 



co soma dis stria gave their sensitiveness to sugars as follows : sucrose, 

 fructose, dextrose, and lactose in decreasing order. The final food 

 test by the caterpillar is the taste of the leaf. The organs of gustation, 

 according to Dethier, are primarily on the epipharynx, but probably 

 also on the hypopharynx. Most young caterpillars do not have to hunt 



