186 MANUAL OF VEGETABLE-GARDEN INSECTS 



length when newly laid. They increase considerably in size 

 before hatching, which takes place in one to three weeks. The 

 larvse feed on the roots of grasses and decaying vegetable matter 

 and sometimes attack the same plants as do the beetles. When 

 mature, the larva is li inches in length, bluish white with the 

 head brown. From six to eleven weeks are spent in the larval 

 stage. The mature grubs construct earthen cells within 

 which to pupate and the beetles emerge two or three weeks later. 

 There is apparently only one generation annually. 



The measures suggested for the control of the carrot beetle 

 are of little practical value. Clean farming and a short rota- 

 tion of crops will under ordinary conditions prevent serious loss. 



References 



U. S. Div. Ent. Bull. 33, pp. 32-37. 1902. 

 Hayes, Jour. Ec. Ent., 10, pp. 253-261. 1917. 



The Black Swallow-Tail Butterfly 



Papilio pohjxenes Fabricius 



The caterpillar of this large black and yellow butterfly feeds 

 on the leaves of celery, parsnip, carrot, parsley, caraway, 



fennel, sweet-fennel, dill, 

 anise and nearly all wild 

 umbelliferous plants. It is 

 most destructive to young 

 celery. The butterfly ranges 

 throughout North America 

 from southern Canada 

 southward through Central 

 America and the West 

 Indies to Venezuela. 



The butterfly (Fig. 109) 

 has an expanse of 3i 



— The black swallow-tail , . • i rpi 



butterfly (Xf). to nearly 4 mches. Ihe 



Fig. 109 



