390 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



therefore that pupation in 1922 occurred mostly during the second and 

 third weeks of May. 



By May 22 flies had emerged from pupae collected on May 15, and 

 flies containing immature eggs were taken in the field on the same 

 day. At this time, some beets were just appearing above ground, 

 while others were not yet planted. By May 31, flies were very common 

 in the fields and some contained mature eggs. On June 1 eggs were 

 found in the soil of a cage in the laboratory, and they were obtained in a 

 beet field on the following day. In loose groimd the female crawls into 

 crevices in the soil near a plant and deposits her eggs singly or in lots 

 of two to forty. In compact soil the eggs will be found just beneath the 

 stirface of the groimd, often in contact with the plant and rarely more 

 than an inch from it. Most of the eggs were deposited during the 

 week of June 1 to June 8, and by June 14 most of the eggs had hatched. 

 The egg of Tetanops is 1.0 mm. in length, 0.25 mm. in width, slender, 

 slightly curved, glossy white, unmarked, and much smaller at one end. 

 Eggs have been found around nearly every beet plant in many of the 

 fields examined. As high as forty were present around some plants. 

 Eggs were also abundant around lamb's-quarters (Chenopodium 

 album), red root (Amaranthus reiroflexus), and the prostrate pigweed 

 (Amaranthus hlitoides). 



By June 14 a few small larvae were beginning to feed on the tap 

 roots, some as deep as three inches. The characteristic black feeding 

 spot and the soil soaked with beet sap were already present, but wilting 

 had not yet occurred. The pre-oviposition period was found to average 

 about ten days and the egg stage covers five days, so it may be said 

 that maggots will begin working on the beets approximately two weeks 

 after the flies appear. 



In nearly all cases where serious infestations of Tetanops have occurred 

 the soil has been sandy or a sandy loam, tho they have been found 

 sparingly in heavier soils. Maggots seem to thrive where the moisture 

 content is very low. Flies will oviposit in dry sand, and the resistance 

 that larvae have to lack of moisture was accidentally shown in an- 

 other way. A flower-pot containing several dozen maggots was mis- 

 placed in the laboratory, and as a result was not watered for about 

 two months. When the pot was examined later the maggots were 

 healthy and crawling around in the dry sand. For some reason, these 

 maggots were still in the larval stage on June 17, as the paper is being 

 written. Another deviation from the above life-history has been 

 found in our rearing work. In August, 1920, and again in 1921 a 

 small number (perhaps 2 to 5 per cent) of the larvae in otu* cages have 



