176 FIRST AJSrXUAL REPORT OF THE STATE ENTOMOLOGIST. 



with the fibrous rootlets, as shown in the figure, whereby it is now 

 these central and not the outer leaves which first turn yellow and 

 die ; and all the upper portion of the root becomes soft and putrid, 

 while the bottom part, continuing to be nourished by the fibrous 

 rootlets, remains sound, and the worms now crowd into this part to 

 feed, whereby it sometimes presents a wonderful appearance, being 



thronged with Avorms wedged together 

 side by side in a com- 

 pact mass, all with their 

 heads downward, eagerly W/j'i//j}]\\\ 

 consuming the last re- Fig. 5i.— 



cp t .-, -ii Baseofan 



mains oi lood there is there, onion crowded 

 and onlv the rounded hind 7'^^ ^<l'\'"g 



larvpe (alter 



J !^;^ .7^- ends of their bodies exposed Fitch). 



Fig. 50 -Onion bulb with the lar- to vicw, these forming an even surface 



vsB in the ground adjacent (after ' '=' 



Fitch). similar to the cobble-stones of a street 



pavement, as represented in Fig. 51." 



Although the onion, in all its stages and in its different varieties, is 

 subject to attack, yet the fly occasionally selects a limited locality or 

 even a particular onion for the deposit of its eggs. Dr. Fitch has 

 given a remarkable instance which illustrates this selection : ^' An 

 escallion, a month after it was set out, having wilted and turned yel- 

 low, the whole of its root was found to be a soft putrid mass of a most 

 offensive smell, everywhere thronged with these maggots of all sizes, 

 some of them newly hatched and no larger than the eggs from which 

 they came, others full grown, and others changed to pupa? and lying 

 in the wet dirt in contact with the root. I judged that there was up- 

 ward of two hundred of these maggots in this one onion, which was 

 little more than half an inch in thickness. And though there was 

 now no sustenance remaining for their nourishment, unless they fed 

 upon the putrid as well as upon the sound substance of the onion, 

 every crevice above ground, around the bases of the leaves, was occu- 

 pied with eggs to the number of about fifty, and many empty shells 

 from which worms had recently issued. It was a mystery to me why 

 such a multitude of worms should occur in this particular onion, and 

 why flies continued to deposit their eggs upon it, when it was already 

 so overstocked as to furnish no food for their young." 



Insect Enemies. 



No parasite is known to prey upon the onion-fly. In Europe there 



is a small four-winged Ichneumon fly, Alysia vianducator Panzer, 



which destroys its pupa. It has not been detected in this country, 



but the genus is represented by at least three determined species* of 



*Pioc. Entomol. Soc. Phila., i, p. 211, 1862. 



