Rhynehaut — Life-History and Bionomics of the Flax Flea-Beetle. 529 



yellow region in their centres ; and the anal hooks yellowish-brown at the 

 tips. The development of pigment in the eyes offers a useful means for 

 determining the age of individual pupae. 



(^) Characteristics of the neiuly emerged Adult. — Colour, white or greyish 

 white, with greyish black head, black eyes, and yellow femora. After three 

 days it is greyish black all over; and after a further three days the normal 

 colour has been assumed. Newly emerged beetles can therefore be easily 

 recognized in late summer when they appear above ground. They are not, 

 however, seen until the colour has become dark-grey or brown, as they remain 

 in the soil for the first few days of adult life. Just after emergence they 

 can jump tolerably well, but they walk with difficulty. 



{j) Duration of the Life-cycle. — The transformations from oviposition to 

 the emergence of the adult are thus completed in from fifty-seven to sixty- 

 five days. 



The figures in the following table are taken from records of rearing 

 experiments : — 



de- 

 posited. 



Hatched. 



Incu- 

 bation 

 period. 



Fully 



fed 



larva 



in soil. 



Feeding 

 larval 

 stage. 



Pupa 

 formed. 



Length 

 of non- 

 feeding 

 larval 

 stage. 



Adult 

 emerged 



Length 

 of pupa 

 stage. 



Total 

 from 

 egg to 

 adult. 



Days 

 17 



16 



17 



16 



25.6.21 

 1.7.21 

 7.7.21 



10.7.21 



Days 

 23 



27 



27 



28 



12.7.21 

 20.7.21 

 25.7.21 

 29.7.21 



Days 

 12 



12 



12 



13 



57 

 61 

 62 

 63 



if) Hihernation of the Adults. — As soon as the weather gets cold, feeding 

 ceases, and winter quarters are secured. Hibernation occurs beneath the 

 slielter of grass, weeds, moss, &c., near dry fences in the neighbourhood of 

 the fields which supported them during the previous weeks. Hibernating 

 beetles are also found in crevices in walls, gate-piers, woodwork, &c. ; in 

 outhouses, adjacent to flax fields, and even far out in fields from which flax 

 has been pulled, if these are provided with old grass and weeds to afford 

 shelter. In January, 1921, the writer made a study of the hibernating 

 quarters, and found beetles in the different places as stated. Some go down 

 into the soil for a sliort distance, while others are found in crevices and 

 cracks in the soil, or even on the surface beneath grass, &c. When first seen 

 they are quite inactive, with the legs gathered underneath the body, and the 



