THE ORANGE THRIPS. ( 
Eggs, larvae, and adults are found on the trees, and pupae in the 
dead leaves under them, from early May until early November, all 
four forms being present during the entire period. The broods thus 
overlap so closely that it is very difficult to separate them. 
INTERRELATION OF ABUNDANCE OF THRIPS AND FOOD PLANTS. 
The orange thrips feed only on very tender plant tissues, namely, 
the young leaves, shoots, and tender fruit. This makes it necessary 
for them to pass from foliage to fruit and from plant to plant as the 
suitability of the tissues as food changes. They first make their 
appearance in April and May on the new growth of the Navel orange, 
reaching the first maximum of abundance about the time four-fifths 
of the petals are off. When most of the petals have fallen a few 
thrips pass to the more advanced fruit and the number feeding on 
the latter rapidly increases as the first growth of foliage becomes 
hardened and distasteful. The thrips continue feeding on the fruit 
until the latter, in turn, becomes somewhat tough, and reach a second 
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FIG. 1. — Diagram illustrating the relative abundance of orange thrips on oranges, on 
orange foliage, and on other plants during the season. (Original.) 
and greater maximum in May, June, and July. They then pass 
once more to the succulent growth which has come on in the mean- 
time, and reach the third and final maximum of concentration in 
August and September. 
As the first citrus growths are becoming tough and before the fruit 
is quite tender, the thrips begin to work on the leaves of the grape, 
pepper tree, umbrella tree, and some uncultivated plants, reaching 
a minor maximum of abundance on these at the time of greatest 
abundance of tender leaves and stems. A second maximum of concen- 
tration is reached on some of these secondary food plants in the fall, 
when most all of the summer growths on citrus trees have become 
tough. 
The relative abundance of the orange thrips on its various food 
plants, at different times during the season, is shown diagrammatic- 
ally in the accompanying chart (fig. 1) ; the diagram represents the 
results of observations made at regular intervals in different parts 
of the Tulare County citrus belt. 
