Biology of I. ricinus 297 



which have thus dropped from the host mate again with one or more 

 males placed in a vessel. It is probable that this occurs in nature, 

 since it has been observed in other species (canisuga, angustus, putus). 

 Having fallen upon the grouud, and being abandoned by the male, the 

 female proceeds to find shelter beneath the surface vegetation or stones, 

 or she may burrow into the loose soil. She is fairly active at first and can 

 climb up smooth surfaces like glass to an astonishing degree considering 

 the hugely augmented weight, due to the great amount of blood which 

 she has ingested. If placed in a glass jar covered with gauze and con- 

 taining earth at the bottom, in the centre of which is placed a tuft of 

 grass, which is occasionally sprinkled with water, it will be seen that the 

 females congregate about the grass roots in chinks and crevices in the 

 earth, and that they lie there very quietly for days or weeks before the 

 eggs begin to appear. The time when oviposition takes place is 

 largely influenced by temperature, being greatly retarded by cold. 

 We shall presently consider the mechanism of oviposition and its 

 duration, for the latter is also markedly influenced by temperature. 

 The eggs are next observed in small heaps lying upon the antero-dorsal 

 surface of the female and their number increases from day to day. 

 Slightly gorged females lay fewer eggs than do the fully gorged 

 specimens, and the few eggs they lay usually do not hatch out. From 

 this it may be gathered that such females are not fertilized or that their 

 eggs are otherwise imperfect. The eggs are usually very numerous, 

 numbering hundreds or a thousand or more (see PI. VII, p. 310). 



Following upon an interval of varying length, this again depending 

 upon temperature, the process of hatching commences. From the egg- 

 shells emerge vast numbers of larvae. If they hatch out in a glass 

 vessel containing grass the larvae climb up the grass blades and con- 

 gregate in masses upon the tips of the leaves, or form clusters on the 

 under side of the gauze which encloses them in the vessel. In nature 

 they behave in a similar manner, that is, they climb to the tips of the 

 grass blades and the adjacent vegetation. 



The larva is hexapod, and possesses neither respiratory nor sexual 

 organs. After it emerges from the egg its chitin requires some time to 

 harden and darken, and during this period it assimilates the yolk-mass 

 derived from the egg. When the larva has exhausted this reserve food- 

 supply, it attaches itself to a host and proceeds to suck blood. When 

 replete, after 4 to 5 days 1 , it releases its hold, and, falling to the ground, 



1 It is possible that the period of attachment to the host may be prolonged in the 

 various stages by cold weather. Observations in this respect are lacking. 



R. I. ' 20 



