568 SUMMARY OF CURRENT RESEARCHES RELATING TO 



centage then falls until it reaches its second minimum early in August. 

 The fact that the variations in percentage of glycogen to a large extent 

 run parallel with the variations in weight somewhat masks the seasonal 

 alterations. 



The results seem to indicate that glycogen is being stored from 

 August to October, probably as a provision for a period of lessened 

 activity of absorption during the colder months. The second rise in 

 percentage is probably preparatory to an increased functional activity 

 with a correspondingly increased destruction of glycogen during the 

 hotter months of the year. 



Arthropoda. 



a. Insecta. 



Tropisms of Insects.* — C. T. Brues points out the danger of study- 

 ing responses in the laboratory without careful reference to behaviour 

 in nature. Much is said about the negative geotropism of insects — 

 they persistently seek the top of the jar in which they are kept captive. 

 But this negative geotropism becomes an absurdity as soon as we attempt 

 to apply it in a general way to insects in their natural environment. It 

 vanishes. Crawling insects do not congregate at the tops of objects 

 in their environment, and flying insects do not seek high altitudes. 

 The flight of the humble-bee shows neither geotropism or phototropism, 

 but catch it in a net and it is a marked instance of negative geotropism. 

 There is an instinct to seek the open whenever disturbed, and this 

 usually means flying upward and toward the light. 



Bees of the parasitic genus Gcdioxys fly downward when caught in 

 the net. This may be connected with its habit of entering the nests 

 of other bees to lay its eggs. " In the event of its discovery by the 

 rightful owner of the nest, it may drop to the ground with much better 

 chances of escape than it would otherwise have." 



Terrifying Attitude of Eyed Hawk-moth.f — Arnold Japha de- 

 scribes the " Trutzstellung " of Smerinthus ocellatus, and gives a correct 

 figure. During the day the moths remain seated quietly on the stems 

 of willows and other trees, or hanging from the branches. The eye- 

 spot and the rose-red part of the wings are quite hidden, and the moth 

 is like a group of dried willow leaves. Under stimulus it assumes in- 

 stantaneously its terrifying attitude : the spot and the red are displayed, 

 the thorax is arched up, and the abdomen curved. At the same time 

 there is the curious energetic rhythmical movement — protruding and 

 retracting the front of the body — which lasts for a few seconds or half a 

 minute. Then it goes to rest again with almost imperceptibly slow 

 change of position. Standfuss gave specimens to nightingale, red-breast, 

 blackcap, and other birds : four out of five were obviously frightened 

 when the terrifying attitude was assumed. They left it alone after one 

 trial. 



* Amer. Nat., xlii. (1908) pp. 297-302. 



t Zool. Jahrb., xxvii. (1909) pp. 321-8 (1 pi.). 



