70 THE MONTHLY BULLETIN. 



showed that more than 84 per cent were infested with one or more 

 larv£e or pupa3 of this insect ; and it was not known that the insect 

 occurred in that part of the state. 



LIFE HISTORY OF THE INSECT. 



The life history of this insect in California is, briefly, as follows : 

 During the summer and fall the small whitish larvaj may be found in 

 the wheat stems, usually close to or actually in one of the joints. Any 

 part of the stem may be infested but the larvae are most commonly found 

 near the third joint. As early as September some of these larvge change 

 to the pupal stage but many remain in the larval stage until January 

 or February. In January, however, most of the insects will be found 

 to be in the pupal stage. 



About February 1st the first generation of adults begins to appear. 

 These are small, black, wingless insects, looking so much like ants that 

 the ordinary observer would readily believe them to be ants. They 

 soon deposit eggs in the young plants of winter wheat, placing them, 

 with remarkable accuracy, close to the young wheat head which at this 

 time is just beginning to develop in the heart of the plant. The larvae 

 that hatch from these eggs work within the short stem of the plant and 

 in a short time destroy the most vital parts, including the embryonic 

 head. The larvae soon become full grown, pass quickly through the 

 pupal stage and very early in the spring — late in February or early in 

 March — the adults of the second generation begin to appear. 



The adults of the second generation are winged and scatter over the 

 field or into near-by fields. The females often select the largest, most 

 vigorous plants in which to lay the eggs that are to produce the larvae 

 which will live through the summer, and change to the over-wintering 

 pup^e in the fall or early winter. 



CHARACTER AND EXTENT OF THE INJURY. 



The larvae of the first generation usually do the most damage, as they 

 attack the wheat when it is very small, often killing the whole plant. 

 If the plant is not killed, the earliest, strongest central stalk is destroyed 

 and the plant stools excessively. The crop that develops must come 

 from these stools, which develop weaker and later stems than are found 

 on the uninjured plants. If the stand is already poor the loss of many 

 plants due to the attacks of this insect may be serious ; or the loss of time 

 due to the fact that the stalks which develop from the stools mature 

 later than the others, may be important, especially in a dry season. 



If the adults of the second generation lay their eggs in very young 

 wheat, the effect of the work of the larvas wall be much the same as that 

 described for the larvae of the first generation. The small plants will 

 seem to grow well for a while, the lower leaves being especially strong 

 and vigorous, but the stem remains short and the whole plant may die or 

 stool excessively. If the wheat is older, the effect of the presence of the 

 larvae in the stems is not apt to be as serious — at least it is not as 

 apparent. The infested plants may form heads which may or may not 

 become well-developed. Usually the presence of a larva in a stem 

 causes more or less thickening of the walls of the stem and the upper 

 part of the plant is not well nourished. The heads that form on such 

 plants are usually small, or the kernels do not fill out well and a light 

 crop, or a crop of small, shrunken grain, is the result. 



