60 



per cent, in the spring of 1912 and 47-5 per cent, in that of 1913. As^ 

 control was only begun in 1913, this reduction was evidently due to- 

 natural factors. Though Lang has shown that in the forests of Upper 

 Franconia the larvae of Raphidia ojyJiiojJsis attack the eggs and young 

 larvae of C. abietis, this enemy could not be held accountable for the 

 decrease, as it was only rarely found and only a small number of 

 Ichneumonid parasites were obtained from a large number of larvae 

 during 1912-1913. At the end of 1914, however, the number of 

 Ichneumonids present in some parts of the forest was considerable. 

 According to Baer, an Ichneumon, Polycinetis aethiops, attacks the 

 nearly full-grown larvae. Though great injury was done to the trees 

 in the forest of Roggenburg, they were not killed, and in 1913 the 

 damage had disappeared to a great extent, only the lower branches- 

 and those in the interior of the tree retaining their bare appearance. 



It is generally supposed that the larva destroys the needles during; 

 June, July and the beginning of August and afterwards shelters in the 

 ground, but this is only partly correct, as some larvae remain longer 

 on the tree than others ; in one case the destruction of the needles< 

 continued right up to December. Effective control hinges on an early 

 knowledge of the date of the flight period. Whether the flight in 

 spring will be considerable or not may be determined in the preceding: 

 autumn by observing th e so-called pupal eyes. According to Scheldt er, 

 larvae that are quite mature exhibit deep black oval spots above the 

 eyes representing the eyes of the future pupa. The author believes 

 this to be only partly correct, as these markings do not appear only 

 just before pupation, but as early as the previous autumn or summer,, 

 and larvae with pupal eyes were found in the month of August 1913. 

 A high temperature in April was found to favour pupation. The- 

 pupal stage in the soil is very short, especially in fine weather. 

 Mating takes place on the ground and on grasses and very rarely in the 

 crown of the tree. 



In the forest of Roggenburg sticky bands about 5 feet above the 

 ground proved very successful at the beginning of a flight. The females 

 rarely fly to the tree-tops, most of them climbing up the trunks. Later 

 on, when the weather allowed the insects to emerge in large numbers,, 

 and the ovaries of the females were full of eggs, the females succeeded 

 in crossing the bands -without being captured. These observations 

 are not in accordance with those of many investigators and require to 

 be continued. Fly-papers gave excellent results, and though their 

 cost prohibited experiments on a large scale, they showed that a 

 substance with the properties of the adhesive used for trapping flies is 

 also suitable against these insects. 



Forbes (S. A.). Recent Illinois Work on the Corn Root-aphis and the 

 Control of its Injuries. — Twenty-eighth Report of the State Entomo- 

 logist of the State of Illinois, Urhana, 1915, pp. 1-62, 18 figs^ 

 [Received 2nd December 1916.] 



The corn root-aphis. Aphis tnaidiradicis, is the most generallv 

 injurious pest of maize fields in Illinois [see this Review, Ser. A, Vol. i, 

 p. 124]. The key to its control is found in the spring condition of this, 

 pest in old maize fields infested in the previous year and m the fact that 

 maize is the only crop on which it feeds. The principal measures- 



