144 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



slowly withdrawn, since the petiole is never found lying straight but 

 is folded back upon itself at the end of the egg, the egg finally resting 

 with petiole down the stem but entirely within the plant tissues. 

 The entire egg is more slender and the petiole is much longer after 

 oviposition. Stems have been dissected, after previously killing the 

 female in the act of oviposition, and the position of the egg noted in 

 relation to the ovipositor. /. tritici eggs require ten days to hatch, 

 though the period of incubation varies with the temperature, cool 

 weather retarding hatching. The larva? molt at least three times and 

 probably four. This can be ascertained by noting the change of shape 

 of the larva, the development of the mouthparts and the number of 

 cast skins, or molts. As many as three cast skins have been found in 

 a single cell with an immature larva. The gall begins to form before 

 the egg hatches and greatly disarranges the position of the fibrovas- 

 cular bundles, which undoubtedly explains why the stems fall. From 

 the time the larvae are hatched until they are about two-thirds grown 

 the tissues^ at the point where the galls occur and immediately above 

 and below, are very juicy and softer than at other points along the 

 stem and remain so until the larvae are about grown, when the galls 

 become much harder and very woody. As the fibrovascular bundles 

 are badly disarranged by the galls, the stem does not have the rigidity 

 at this point it otherwise would have if no galls were present. The 

 plants soon become topheavy, especially if the galls are in the 

 basal joints, and will lodge or fall with the first wind or rain. The 

 stems usually bend over immediately above the gall, since the galls 

 are just above a joint and the stem is slightly more rigid at that point. 

 These galls interfere seriously with the flow of sap and a large amount 

 is undoubtedly intercepted and used as nourishment by the larvae, thus 

 impoverishing the kernels of wheat. 



/. tritici larvae require approximately three weeks to reach maturity 

 after hatching, or a month from oviposition, the time depending largely 

 upon the temperature. /. grande, form grande, larvae reach maturity 

 in less time, since they emerge later and the weather is warmer. 



Twelve species have been tested and all will breed parthenoge- 

 netically; eight are normally so, producing females continuously, males 

 rarely occurring. In fact, one species has been reared continuously 

 through a period of three years and no males have appeared. Appar- 

 ently the males are not highly thought of among the eight species just 

 mentioned since the females never pay the slightest attention to them 

 when they do happen to be present. The other four species are not 

 ordinarily parthenogenetic but will reproduce in this manner, the result- 

 ing offspring always becoming males. It is verj^ probable that all our 

 species, could they be tested, would prove to be parthenogenetic. 



