180 



INVERTEBRATE ANIMALS. 



duced in great numbers at particular times of the year. They then 

 quit the nest and pair, after which the fecundated females lose their 

 wings and form fresh societies. The workers (fig. 125, h) are some- 

 times all of one kind, but they are often divided into two, or even 

 three, distinct classes or " castes." The Ants exhibit many most 

 extraordinary and interesting instincts and habits, of which their 

 custom of " milking " the little Plant-lice has been already men- 

 tioned. Another very singular habit of some Ants may be just 

 alluded to — their habit, namely, of capturing the pupse of other 

 species of Ants and bringing them up as slaves. The relations, 

 however, between the masters and slaves vary a good deal in dif- 

 ferent cases. In the case, for instance, of the Russet Ant {Formica 

 rufescens) the masters are so entirely dependent upon their slaves 

 that they cannot even feed themselves, and the only work which 

 they perform unassisted is the capturing of fresh slaves. In the 

 Blood-red Ant (Formica sanguinea), on the other hand, the slaves 

 are much fewer in number, and the masters are much less dependent 

 upon their good offices. In all cases, the slaves exhibit the greatest 

 devotion to their masters, and are invariably taken the greatest care 

 of by their captors. 



Order XII. Strepsiptera. 



This is an extremely small order of insects, which merely requires 

 to be mentioned. It includes only certain minute parasites, which 

 are found on bees and other Hymenopteru. The females are desti- 



Fifj. 126. — Strepsiptera. Stylo2)s Spencii, greatly magnified (after Westwood). 



tute of wings or feet, and are merely soft worm-like grubs. The 

 males (fig. 126) are active, and possess a single pair of large mem- 

 branous wings. Unlike the Diptera, it is the posterior pair of wings 

 which is present, and the anterior pair , is quite rudimentary, and is 



