30 INSECT BEHAVIOR 



In all, the larva or grub is full grown in four days from the time it 

 hatches. 



Upon finishing its meal, which lasts continuously for four days, the 

 larva spins a flimsy net work of silken threads inside of which the 

 cocoon proper is spun. This inner cocoon resembles a tiny torpedo, 

 rounded at both ends and ten millimeters in length. It is very neatly 

 constructed of delicate silk and coated all over the interior with a 

 brown varnish that hardens in contact with the air. 



Within this delicate cradle, ten days later, the budding wasp under- 

 goes pupation that wonderful process described more fully in the 

 following chapter by which the footless grub is transformed from a 

 low and ancient form, to the highest order of modern insects. The 

 actual change from gorged grub to a neatly folded, but colorless wasp 

 is affected in ten days, but it still has three hundred and twenty-eight 

 hours of confinement separating it from the light of day, hours which 

 must be passed quietly, lest injury result. 



As the hours go by, color at length flows through its body and 

 appendages, transforming opaque yellow to glistening black. Then 

 comes the final gift of nature, the power of motion. The nascent 

 creature, moist with birth, bursts its cocoon, gnaws through the plug 

 of mortar and issues into the outer world a perfect insect. Only 

 thirty-eight days have passed since I placed the tubes in the 

 laboratory, and since the parents of this new creature arrived, real- 

 izing their destiny. 



There is an interesting problem to solve concerning the black reed- 

 wasps. Their nests vary considerably in number of cells. Some 

 are complete with one, others contain two, but the majority are com- 

 plete only after an egg has been laid upon the stores in three separate 

 compartments. The question arises, How will the wasps emerge 

 as perfect insects without disturbing one another? 



If the nest is to shelter three insects, the cell farthest from the 





