INTRODUCTION. 



103 



changing later to a dull yellowish- white. The egg-stage lasts 

 from 6 to 8 days. 



The newly-hatched larvae feed gregariously for two or three 

 davs, skeletonising the leaves, and afterwards migrating to 

 different parts of the plant, where they commence to eat the 

 entire leaf-substance. The newly-emerged larva is somewhat 

 like a wood-louse in form, and is bright yellow in colour, with 

 a black head. There are six rows of black spots running longi- 

 tudinally throughout the body ; from each of these spots a hair 

 arises. Each of the thoracic segments has a pair of black legs. 

 On the first thoracic segment is situated a black shield which has 

 ten anterior projections. There is a yellowish pseudopod (pro- 

 trusible sucker) at the anal extremity, provided with projections 

 which aid the larva to adhere to, or clasp, the leaves. The full-fed 

 larva differs from the newly-hatched larva by being greenish in 

 colour and larger in size ; it varies from 21*9 mm. to 25*7 mm. 

 in length, and from 7*5 mm. to 8*3 mm. in breadth. The anus 

 is situated just above the base of the protrusible sucker-foot, and 

 by curving the terminal segment of the abdomen upwards, 

 the larva deposits its excrement on its body, whence the excrement 

 is prevented from falling by an exudation from the body. The 

 excreta frequently form a complete covering over the larva. 

 When disturbed the larvae roll themselves up into a ball some- 

 what after the manner of a wood-louse. The larval stage lasts 

 from 1 1 to 18 days. 



When full-fed the larva generally enters the soil for pupation. 

 Prior to its transformation, it makes an oval cocoon of particles 

 of earth, within which it pupates. The average length of these 

 cocoons is 18 mm. and the average breadth 12 mm. The depth 

 at which the cocoons are found varies from two to six inches 

 according to the condition of the soil. Occasionally cocoons are 

 found underneath rubbish and pieces of wood. The pupal stage 

 lasts from 14 to 29 days. 



The adult beetles as well as the larva? avoid sunlight, and are 

 usually found on the under surface of the leaves. They feed 

 intermittently both by day and by night. They do not fly readily, 

 and even when thrown into the air frequency make no attempt 

 at flight. When disturbed on the leaves they usually drop to tho 

 ground, and for a short time feign death. The life of the female 

 beetle varies between 53 to 168 days. The cycle from egg to 

 pupal stage covers a period varying from 31 to 55 days. 



England. 



Phijllotretn nemorum, L. Turnip Elea-beetle. 



The following is taken from Rev. Appl. Ent., ser. A, vol. iv, 

 1916, p. 10.8, where will be found an abstract of an article on 

 "Flea-beetles" in the Botanical Journal. London, iv, no. 4, Jan. 

 1916, p. 49:— 



The adult beetles hibernate during the winter under the bark 



