46 



when larvae or adults are noticed as hopping abundantly, and it seems 

 from results of this season's work that the greatest numbers of hop- 

 pers are captured in the afternoons of warm days, with little or no wind, 

 the hoppers seeming to jump best between 3 and 6 p. m. 



Further tests of the tar pan have confirmed its value in destroying 

 these pests, and a field test made with the cooperation of the farm 

 department of the Experiment Station, and reported in full in Bulletin 

 19, Iowa Experiment Station, has shown that its use will practically 

 enable the farmer to keep a larger number of cattle, sheep, or other 

 animals upon grass land. In the experiment referred to, the result 

 showed a gain of 68 per cent, but inasmuch as the experimental plat 

 lay alongside other grass land and was subject to invasion from this, 

 it seems to me that by a continued use of the treatment and over whole- 

 pastures, so as to preclude migration of insects from adjacent areas, we 

 would get a still better result, and while it is perhaps too much to 

 hope to get an increase sufficient to double the number of animals pas- 

 tured on an ordinary field, I should hope to secure some such propor- 

 tion, at least, if other destructive insects were also kept within bounds. 



Another very widespread and destructive species is the Dicdroccphala 

 mollipes, and this has been the subject of a thesis study by Mr. J. A. 

 Rolfs, a senior student in entomology here this year. The main facts 

 in its life history may be stated in brief in this connection. The eggs 

 in fall are mostly deposited in the rank grass of low ground, the insects 

 preferring low ground during dry weather, which usually prevails for 

 a few weeks in autumn. The larva3 hatching in spring, during May or 

 early June, become adult by the latter part of June or early July, and 

 in ordinary seasons will largely migrate to higher ground and deposit 

 eggs, so that the second brood of larvae, which appears in September, 

 for the most part will be found widely distributed on both high and 

 low ground, and may cause great damage. These larvae mature by 

 early October, and the imagos will, many of them, move to low ground 

 to deposit eggs. It is evident that the burning over of sloughs and 

 swampy or low ground is very desirable in the treatment of this 

 species. 



Plant-lice have been very plentiful during the autumn mouths, a 

 strong contrast to their scarcity during the early part of the season. 

 I had hardly returned from the Rochester meeting, where I reported a 

 scarcity of these insects, when they became very conspicuous in their 

 abundance. 



Myzus persiem on wild plum trees was among the species most notice- 

 able, but the injuries it caused were by no means so severe as occurs 

 when it is abundant in the early part of the season and attacks the 

 growing twigs and the fruit. 



Aphis brassicw was specially noticeable on Rape, where it caused a 

 considerable amount of damage, rendering the crop unfit for feeding. 

 It was quite numerously infested with parasites in late autumn. 



