490 



Bulletin 78. 

 THE INSECT'S APPEARANCE. 



The larva or maggot — Everj^one who has had any experience 

 with this pest is familiar with it in this — the maggot or larval 

 stage. And yet, we have not been able to find an illustration by 

 which the maggot could be definitely recognized. The only ob- 

 servers who have given us definite descriptions of this form of the 

 pest are Bouche (who gave the insect its name in 1833), and Dr. 

 Fitch (in 1867) ; all other descriptions are either inadequate or 

 evidently compiled from these authors. 



The maggots, from their birth, are similar in form to the full 



grown one represented in figure 2, and are always footless and of 



a shining white color, sometimes tinged with yellowish. The 



body is cylindrical, tapering to the cephalic end where the two 



strong, black, parallel, curved, rasping jaws project downward ; 



these hooks are connected with an internal blackish framework 



which is indistinctly visible through the skin of the maggot (Fig. 



9). The caudal end of the body ends bluntly, appearing as 



though cut off obliquely downward and backward. 



A full grown maggot measures .32 of 

 an inch (8 mm.) in length. On each 

 side of the body just back of the head 

 is a minute, light brown, fan-like pro- 

 jection, or spiracle (shown greatly en- 

 larged at b in figure 2) which leads into 

 the trachea or breathing organs of the 

 maggot.* These trachea extend the 

 length of the body in two main trunks 

 which throw out many ramifying 

 branches, and again open to the sur- 

 face near the center of the flat oblique 

 caudal end of the maggot in two raised, 

 roughened, darker brown or blackish 

 spiracles shown near the center of 

 figure 2, a. Around the margin of this 



Fig. r. — TheCabhage Root Maggot, 

 side view, enlarged ; the hair line 

 beneath represents the natural 

 size. a, dorsal view of caudal 

 segment, showing size, number 

 and arrangement of fleshy tuber- 

 cles, much enlarged ; b, outline of 

 a cephalic spiracle, greatly en- 

 larged. 



flattened caudal end of the maggot there are 12 fleshj^ pointed tubercles ; the 

 two lower ones are larger, of a brownish color, and alwa3's bifid or two- 



*Bouch6 describes these cephalic spiracles as having 7 to 9 divisions. This seems to be 

 true of the young larvte (those about one-half grown), but in full grown specimens we find 

 the number to be usually 12. The number varies slightly and thusmay not prove of much 

 specific value. 



