12 ' UNIV. OF N. H. AGR. EXPERIMENT STATION [Biilletin 221 



The studies in New Hampshire are planned to supplement these and to 

 supply information as to details of life history under the conditions pre- 

 vailing in the more northerly state. 



The European corn borer continues to develop two generations under 

 New Hampshire conditions. The species overwinters in the larval stage 

 in the stalks of weeds, in corn stubble, and similar situations. When 

 spring is well under way these larvae transform to pupae. This year the 

 date of first pupation was May 18, as compared with April 28 last year, 

 which, in turn, was to be compared with May 4 of the preceding year. 

 The last larva to enter the pupal stage transformed this year July 13, 

 as compared with July 14 last year. The first adult from the overwinter- 

 ing generation emerged this year June 10, as compared with July 30 last 

 year. These dates are a little later than those for the preceding year. 



The eggs laid by these adults constitute the beginning of the first 

 generation of the current year. The first eggs were laid this season June 

 14, which is five days earlier than last year; and the last eggs were laid 

 August 3, which is eleven days earlier than last year. The first larva 

 hatched June 22, as compared with June 27 last year; and the last larva 

 hatched July 27, as compared with August 24 last year. The larvae of 

 this year reached the several stages a few days earlier than those of last 

 year. Pupation began July 21 this yesir, as compared with July 26 last 

 year and .as compared with July 19 the preceding year. Pupation ended 

 August 27. The first adult emerged August o, which is four days earlier 

 than the corresponding record for the preceding year. The last adult 

 emerged September 13. 



Eggs laid by these adults constitute the second generation of the pres- 

 ent year as well as the overwintering generation. Egg-laying began Au- 

 gust 9 this year, which is two days earlier than last year and three days 

 earlier than the preceding year. The first larva hatched August 19, 

 which is three days earlier than the first larva of last year or the j^ear 

 before. 



In studying the records of three consecutive years it is found that 

 about 60 per cent of the borers exhibit two generations under New Hamp- 

 shire conditions. A further and still more interesting fact has come to 

 light: namely, that only a small percentage of the second generation of 

 larvae are able to overwinter successfully. Such of these larvae as do 

 survive the winter and pupate successfully the next spring, develop into 

 adults of small size, which appear to be capable of producing only a rela- 

 tively small number of eggs. Apparently there is a limiting factor here 

 in relation to normal increase of this species under field conditions in 

 New Hampshire. It covers a wide territory; but the intensity of infes- 

 tation is light. This should not be taken to mean that the insect will 

 continue at a relatively low level of abundance. Such may prove to be 

 the case; but much further information will be required before such a 

 conclusion may be safely drawn. The relatively light intensity of infes- 

 tation may easily prove to be temporary. 



It is planned to continue the studies along the lines already followed 

 and to extend the inquiry as conditions make this possible. 



The Stalk Borer 



A study of this insect was begun in 1923 by P. R. Lowry, and has been 

 carried forward in further detail the present year. A considerable 



