100 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 
TOTAL DEVELOPMENTAL PERIOD. 
The total developmental period varies from 20 to 28 or 30 days in 
the majority of individuals, although in those individuals of each 
generation which hold over for a time after the normal time of emer- 
gence it may be from twice to several times as long as this. This 
portion of the life history was actually determined for only three 
individuals. One of these required 22 days and the other two 23 
days each. One other was carried through the total period with the 
exception of the incubation period. Estimating this at 5 days the 
total developmental period for this individual was 36 days. During 
the time it was developing, April and May, the weather was very cold 
and the larval period was 22 days in duration. 
EXTENT OF DAMAGE. * gy 
So serious a menace is this insect to the peach and plum trees that, 
in a favorable season, the trees are completely defoliated in August. 
Morgan figures a plum orchard which was practically defoliated as 
early as May 22, 1897, when the photograph (Pl. XI) was taken. 
In the struggle to repair the damage of the slugs, the trees keep 
putting out new leaves and forming new wood, which causes 
enter the winter unprepared and less able to withstand free. 
Many of them are thus winter-killed. 
Morgan (loc. cit.) quotes a letter from a correspondent in central 
Louisiana, in which the statement is made that the species ‘‘kills an 
orchard effectually in about two years.”’ 
He also makes the following observation: ‘‘The attack of this insect 
upon the American type of plums, such as the Mariana, and the almost 
entire immunity of the Japanese varieties is very noticeable. Peaches 
seem worse affected upon the lighter soils of the State.”’ 
A heavily infested tree has a very characteristic appearance in the 
late season, being entirely bare of foliage except at the tips of the 
twigs, where tufts of new leaves appear. 
NATURAL ENEMIES. 
Although the nauseous, slimy covering of the larva of this species 
undoubtedly protects it from many insects-and other animals which 
might otherwise attack it, it is not entirely without natural enemies. 
Morgan (loc. cit.) mentions two species of mud daubers, which were 
observed constantly visiting the infested trees and carrying away 
the larger larvee, and records the bordered soldier-bug (Stiretrus 
pulchella [=anchorago Fab.]) as feeding on them. He also records 
having observed a hymenopterous parasite, Trichogramma minutum, 
ovipositing in the eggs of the sawfly. The adults of the parasite 
appeared in 8 days (May 22 to May 30, 1896). 
