ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 715 



incorporated. The interior is smooth grey silk. The tubes are closed 

 at their outer end, and are connected at their basal end with round holes 

 leading into galleries in the horn. The skull was picked up on the 

 ground in British East Africa by the Smithsonian African Expedition. 



Procession and Pupation of Larvae of Cnethocampa pinivora.* 

 T. (i. Edwards describes a series of observations made at Arcachou, with 

 a view to clearing up certain points in regard to the processional larvae 

 of Cnethocampa pinivora. The procession is always single file, the larvae 

 being arranged in head-to-tail contact. The length of the procession 

 varies greatly, but only three were found which numbered over a hundred 

 individuals. Experiments were made to determine how far the primite, 

 or the first on the file, may be regarded as the true leader. It was found 

 that any larva might function as primite, but that one individual usually 

 retained the post, and was apparently capable of taking a certain initi- 

 ative in the selection of a path, burrowing for pupation and forming a 

 circulating mass. Light and surface seem to be the determining factors 

 in the choice of a path. A whole procession was cast into shade, and a 

 reflected ray of light was cast under the head of the primite. The whole 

 procession followed the ray, though only the primite could have been 

 influenced by the stimulus. 



Before pupation, the procession breaks up into a mass in which the 

 larvae are continually moving about among each other without advancing 

 from the same spot. This formation was observed at other times also ; 

 and when the procession reformed without pupation, the same larva took 

 the lead and followed the outward-bound thread back to the nest. 

 Artificial threads, or threads of other processions, placed in his path were 

 always rejected. Artificial breaks in the thread did not prevent joining 

 up if the distance between the two parts of the procession was not great. 

 Head-to-tail contact seemed of more importance in keeping the procession 

 together than the thread. Before pupation, the mass formed in a position 

 apparently selected by the primite, which was observed to test the con- 

 sistence of the sand with its mandibles. The whole mass rotated until 

 a gradually deepening depression was formed in the sand. All the while 

 the larvae were depositing their silken threads until a regular network 

 was formed, and in this the loosened sand became entangled. The larvae 

 seemed to aid in the process by displacing the sand with their mandibles, 

 and in a few days the whole mass was buried to a depth of several inches. 

 Pupation was completed nineteen days after burrowing. Larvae which 

 had become isolated buried themselves by means of their mandibles. 

 The facts seem to the observer to warrant the conclusion that, though 

 the individuals of a procession may act alike when influenced by the same 

 stimuli, yet each larva is capable of independent action, and that there- 

 fore the procession cannot be said to act in any real sense as a single 

 individual. 



Effect of Centrifugal Force on the Development of Beetles.f 

 R. W. Hegner has made some interesting experiments on the eggs of 

 Chrysomelid beetles, such as Galligrapha multipunctata and Leptinotarsa 



* Proc. Cambridge Phil. Soc, xv. (1910) pp. 431-6. 

 t Rep. Michigan Acad. Sci., xi. (1909) pp. 123-5. 



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