480 SYNOPTIC COLLECTION. 



upon and renders it motionless. With these paralyzed 

 animals she stocks the burrow ; she then deposits an egg 

 and closes it. When every egg is laid her life work is 

 accomplished. No one can read the admirable observa- 

 tions and experiments of the Peckhams 1 without feeling 

 that the solitary wasps offer remarkable instances of 

 inherited instinct and of reasoning intelligence. It is 

 interesting to note that the inherited instinct is much 

 more flexible than has been generally supposed, and is 

 often modified by individual judgment and experience. 



Sphex ichneumonea Linn. (No. 1224 9 ; No. 1225, <), 

 another fossorial and solitary wasp has the thorax fas- 

 tened to the abdomen by a slender peduncle, the length 

 of which varies in different species. The female stocks 

 her burrow with the green grasshopper, Orchelimum 

 vulgar e (No. 1027). 



The solitary wasp, Odynerus, makes its nest (No. 

 1226) of clay while other species of this genus fill up 

 key holes and the like. 



The most specialized of the solitary wasps are the 

 Mutillidae. The thorax in the winged males (No. 1227, 

 Mutilla occidentalis] exhibits the suture between the three 

 segments as in most insects, but in the wingless females 

 these sutures have become obliterated. This consolidated 

 and sutureless condition is evidence of specialization by 

 reduction and is suggestive of the evolutionary history 

 through which this species has passed. 



The most simple social conditions are found in the 

 beginnings of a colony where the female makes a nest, 

 lays her eggs, and instead of dying, lives on and works, 

 taking upon herself the entire care of the young, doing 

 all the tasks incident to family life, until the first brood 

 of young (which are all females specialized by reduc- 



1 Instincts and Habits of the Solitary Wasps, by George W. and 

 Elizabeth G. Peckham, Wisconsin Geol. and Nat. Hist. Survey, 

 Bull. no. 2 (Sci. Ser., no. i). 1898. 



