2s<) Bionomics of Weevils 



England from the beginning of April fco the beginning of July, and in 

 Scotland from the middle of May to the end of August. 



The larval 'period. The young larva escapes from the egg by making 

 an irregular hole at one end, and must then burrow to the roots of the 

 plant, as on May 21st in a field in Kent, I found very young larvae 

 measuring 1 mm. in length inside the nodules of the pea roots some 

 distance below the surface of the ground. The larvae were to be found in 

 a curved position inside the small nodules, but I failed to detect their 

 presence from the external appearance of the nodule, and it was only 

 by opening a large number with a needle that I found them. The larva 

 must enter the nodule when newly hatched by a minute hole which is 

 not easy to trace. I found several nodules with small holes in them but 

 these were emptied of their contents and contained no larvae. When 

 about quarter grown the larvae are to be found feeding freely upon the 

 root nodules. On June 3rd larvae of different sizes were abundant at 

 the roots of peas and beans in Kent, and one had already ensconced 

 itself in an oval cell in the earth preparing for pupation. The larvae were 

 always to be found amongst the root nodules, usually with their body 

 partly buried in them. As many as six to nine larvae often occurred at 

 the roots of a single plant in Kent and the nodules were much destroyed 

 in consequence. By the middle of June in some pea fields in Kent, 

 scarcely any nodules in a healthy condition were to be found on the 

 roots, and the hollowed out ones that remained testified to the working 

 of the larvae. In such cases no young larvae were to be found at the 

 roots, so doubtless when a severe attack has already occurred many of 

 the larvae resulting from later laid eggs will die from lack of food. In 

 the north of Scotland larvae in various stages of growth were common 

 at the roots of beans in the end of June, and full fed larvae were common 

 on July 24th. Full grown larvae and even a few half-grown ones were 

 still to be found in this locality on September 2nd, but the majority 

 by this time were in the pupal stage. 



Field observations would roughly indicate that the time taken for 

 the growth of the larva from hatching till pupation does not exceed six 

 or seven weeks, judging from the fact that in Kent the weevils com- 

 menced egg-laying in the beginning of April (the eggs taking three weeks 

 to hatch), and the first pupa in the same locality was observed on 

 June 10th. To determine the duration of the larval period more exactly, 

 I carried out the following experiment in Scotland in one of the large 

 breeding cages already described, in which peas had been grown from 

 seed. I placed in this a large number of eggs laid between the 25th and 



