go . A Guide to the Zoological Collections in the 



appendages: — (i) on the prothorax a pair of jointed legs, 

 (2) on the mesothorax a second pair of legs and a pair of 

 wings, and (3) on the metathorax a third pair of legs and 

 a second pair of wings. The modifications undergone by 

 the legs for running, leaping, burrowing, clinging, swim- 

 ming, for seizing prey, for protection by resemblance to 

 other natural objects, are too numerous to be mentioned 

 here : they should be studied in the exhibits of the typical 

 groups, along with the modifications, degenerations, and 

 • suppressions, that occur In the wings. The structural 

 details of the Insect leg should be studied in the dissected 

 preparation of the Grasshopper in Case 75B. 



The abdominal segments In the typical adult nsect are 

 all destitute of appendages, but In some larvae [e.g.y cater- 

 pillars) stumpy legs (" prolegs") are found. 



The last one or two abdominal appendages are pro- 

 longed in the males (and females) of some msects as rods 

 or pincers, and In the females alone of some Insects as 

 stings and ovipositors. 



In most Insects, as in many Crustacea, the main devel- 

 opmental changes. Instead of being completed within the 

 tgg, are continued long after the embryo has been hatched 

 and has become an Independent individual. In these In- 

 sects the adult form Is reached only after a series of moults 

 or " metamorphoses". The typical as well as the most 

 familiar series of Insect metamorphoses ("complete meta- 

 morphosis ") occurs in the Butterflies and Moths, In which 

 the embryo leaves the egg as a worm-like " larva^\ or 

 caterpillar. After feeding voraciously for some time the 

 larva encysts Itself, either In a simple chitlnous envelope 

 or In a silky "cocoon", and remains for a time quiescent as 

 a ^^ pupa'\ or "chrysalis ". In the quiescent pupa stage 

 the post-embryonic development Is completed, the perfect 

 winged insect at length emerging as an " imago ". 



The number of species of Insects Is so vast that to ade- 

 quately Illustrate the group within the limits assigned to 

 it in this Gallery would be an Impossibility. The objects 

 therefore of the small collections here displayed are to 



