THE CELERY CATERPILLAR. 23 
four to nine days, that the larval period may be passed in the extreme 
South in from nine to ten days, although this is oftener four weeks 
in the North, and that the chrysalis period varies between nine and 
eighteen days. The writer observed the pupal period at Washington, 
D. C, from July 8 to July 18, a total of nine and one-half days in 
hot weather. This gives us a possible minimum life cycle of from 
twenty-two days, in the insect's southern range, to eight weeks 
northward. In the North the insect is double-brooded, and winters 
in the chrysalis stage. In the extreme South there are probably 
three or four generations produced each year. Thus butterflies 
appear in the South in March and April and begin the deposition of 
their eggs, while in the New England States and in similar latitudes 
the butterfly does not appear on the wing until May, and seldom before 
the middle of that month. 
Besides celery, this insect attacks practically all other umbellif- 
erous plants, including carrot, parsley, caraway, fennel, parsnip, 
dill, and related wild plants. It does not appear to attack, except 
in extreme cases, any plant outside of this botanical family. 
NATURAL ENEMIES. 
The principal insect enemies are species of ichneumon flies of rather 
large size, single specimens of which serve to destroy the insect 
in its pupal stage. The best known of these are two species of 
Trogus — exesorius Brulle and exidianator Brulle. Some other natural 
enemies, however, have been recorded. The list includes Apanteles 
lunatus Pack, and a dragon fly, Anax longipes Hagen. 
REMEDIES. 
The conspicuous appearance of the larvae of this species renders 
them what might be called an "easy mark," as they are readily found 
and can be crushed under foot, and no other remedies are necessary 
if the work of destruction is begun before the plants are injured. 
The killing off of the first generation will serve in considerable measure 
to destroy the insects so as to prevent a very large second brood or 
generation, particularly if this can be accomplished over a consider- 
able territory. ' The butterfly is a strong flier, and cooperation is 
necessary to keep the insect in check when it becomes destructive. 
The caterpillar can also be destroyed with an arsenical, either Paris 
green or arsenate of lead, but recourse to these is, as a rule, scarcely 
necessary, owing to the ease with which the "worms" can be hand- 
picked. 
BIBLIOGRAPHY. 
The swallowtail butterfly is considered in most text-books on 
general entomology and in many popular periodicals on the same 
topic. A list of technical references is given in Scudder's Butterflies 
66513°— Bull. 82—12 3 
