INSTINCT OF INSECTS. 575 



they do not cut asunder until the intermediate space has been sewed up, 

 and they are ready to step, with their house on their back, upon the terra 

 jirma of the disk of the leaf. In this instance, therefore, the larvae do not 

 wholly separate their case from the leaf, until it is sewed. But when the 

 same larvas cut out their materials from the middle of the leaf, where, 

 though completely cut round, they are retained in their situation secure 

 from all danger of falling by the serratures of the incisions made by the 

 jaws of the larvae, these little tailors vary their mode, and entirely detach 

 the pieces from the surrounding leaf before they proceed to set a stitch 

 into them.^ 



A remarkable instance of variation of instinct in the common house- 

 spider (Aranea domesticd) is mentioned by an anonymous writer in the 

 Zoological Journal. He states that having placed one on a piece of wood 

 fixed in the middle of a glass of water, the spider, finding its other efforts 

 to escape ineffectual, enveloped its abdomen by means of its hinder legs 

 in a loose web which it spun, and then descended at once without the least 

 hesitation into the water, surrounded under its mantle with a bubble of air, 

 evidently intended for respiration as it included the spiracles ; and in this 

 extemporaneous diving-bell, like that of the water-spider (^Argyroneta 

 aquatica) before described, it endeavored to make its escape on every side, 

 but, on account of the slipperiness of the glass, in vain ; and after remain- 

 ing at the bottom of the water for thirteen minutes, it returned apparently 

 much exhausted, as it coiled itself under its wooden platform without 

 motion.^ As we cannot refer so philosophical a contrivance to reason, we 

 must regard it as a variation of instinct ; but certainly, if correctly 

 reported, a very curious one, as the occasion on which the house-spider 

 can want to escape through water must be very rare. 



In the preceding instances the variation of instinct takes place in the 

 same individual ; but Bonnet mentions a very curious fact, in which it 

 occurs in different generations of the same species. There are annually, 

 he informs us, two generations of the Angoumois moth, an insect which 

 has been before mentioned as destructive to wheat : the first appear in May 

 and June, and lay their eggs upon the ears of wheat in the fields ; the 

 second appear at the end of the summer or in autumn, and these lay their 

 eggs upon wheat in the granaries. These last pass the winter in the state 

 of larvae, from which proceeds the first generation of moths. But what is 

 extremely singular as a variation of instinct, those moths which are dis- 

 closed in May and June in the granaries quit them with a rapid flight at 

 sunset, and betake themselves to the yet unreaped fields, where they lay 

 their eggs; while the moths which are disclosed in the granaries after 

 harvest stay there, and never attempt to go out, but lay their eggs upon 

 the stored wheat.^ This is as extraordinary and inexplicable as if a litter 

 of rabbits produced in spring were impelled by instinct to eat vegetables, 

 while another produced in autumn should be as irresistibly directed to 

 choose flesh. 



It is, however, into the history of the hive-bee that we must look for 

 the most striking examples of variation of instinct ; and here, as in every 

 thing relating to this insect, the work of the elder Huber is an unfailing 

 source of the most novel and interesting facts. 



1 Reaum. iii. 112—119. « Zoological Journ.i. 284. ^ (Euvres, ix. 370. 



