988 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Arthropoda. 

 a. Insecta, 



Influence of Magnetism upon Insect Development.*— Mr. J. W. 



Slater in view of the experiments | showing that the eggs of fowls are 

 not normally developed if subjected to magnetic currents during 

 incubation, tried the effect of magnetic action upon the development 

 of caterpillars. Having found six caterpillars of the common large 

 cabbage white, all evidently of the same brood, three of them were 

 put in a box, 5 in. in length, between the opposite poles of two bar- 

 magnets. The other three were placed in a similar box at such a 

 distance that they could not be affected by the magnets. Both boxes 

 were placed under exactly identical conditions as regards light, heat, 

 and supply of food. Two of those between the magnets shrivelled 

 up and died without passing into the pupa-state. Thinking they 

 might have been attacked by some parasite, the author removed them 

 into another box and kept them for some time. As no ichneumons 

 or other parasites made their appearance he dissected the bodies 

 carefully under the Microscope, and found no traces of parasitic 

 injury. 



The remaining caterpillar, and all the three which were not 

 exposed to the magnets, became pupae in due course and came out in 

 May. The non-magnetized ones were perfectly normal and healthy, 

 and when released after examination flew away ; but the survivor of 

 the magnetized set was a cripple. It had merely rudimentary stumps 

 in place of antennae, the wings on the left side were expanded, and 

 the legs on the same side were smaller than those on the right side. 



Flight of Insects.J — Dr. E- v. Lendenfeld some years ago opposed § 

 the theory of Marey tlaat the changes in the shape of the wing during 

 flight were caused by the mechanical action of the resisting air 

 without any muscular action of the insect itself coming into play. 

 This view having been recently contested by some physiologists, the 

 author has made some observations which are well adapted, he thinks, 

 to prove the fallacy of the mechanical theory. 



When at rest the wings of Diptera are more or less askew. When 

 a fly is immersed in turpentine it is immediately made insensible, and 

 lies motionless. Tetanic movements, after a short time, cause slight 

 movements of the legs ; and then the wings, although remaining in the 

 same position relative to the body, turn their face round in such a 

 manner that they firstly become quite flat and then askew in the 

 opposite direction to the original position. This movement is slow, 

 and can easily be observed. When the fly is dead the wings collapse 

 again, and return to their ordinary shape. 



The same movement for which a mechanical action of the resist- 

 ance of the air is considered the sole cause, is here executed in a 

 manner which precludes the possibility of such a cause. 



* Trans. EDtomol. Soc. Lond., 1885. — Proc, p. xv. 



t See this Journal, iv. (1884) p. 861. 



X Proc. Linn. Soc. N. S. Wales, ix. (1885) pp. 986-7. 



§ See this Journal, ii. (1882) p. 184. 



