CalUphoridae 423 



CARE OF FLIES 



As the flies begin to emerge a water fountain consisting of a filled 

 beaker inverted on filter paper in the half of a petri dish is placed 

 within the cage. The water supply must be available at all times. On 

 the day following emergence the flies are given slices of ripe banana and 

 lumps of sugar each in halves of a petri dish. On each succeeding day 

 they are fed fresh sliced liver until egg laying begins. When eggs are 

 desired fresh beef is placed in the cages. 



ESTIMATING THE NUMBER OF EGGS 



A calibrated pipette is useful in estimating the number of eggs that 

 are used. In calibrating it the eggs are separated in 2% sodium hydrox- 

 ide. A number are drawn into the pipette and the volume is noted. 

 They are discharged into 20 cc. of 20% aqueous solution of glycerin. 

 A fractional portion of the suspension is pipetted into water in a petri 

 dish. A portion of the eggs are counted over a bacteria colony counting 

 plate and the number drawn into the pipette is computed. This is re- 

 peated until the volume is determined for the number of eggs desired. 



DISINFECTANTS 



In rearing maggots for surgical use, the eggs are disinfected and the 

 larvae hatching from them are grown on autoclaved food. Sodium 

 hydroxide, formaldehyde, or mercuric chloride may be used for the dis- 

 infection. 



Sodium Hydroxide. Sodium hydroxide is preferred by the writer for 

 its efficiency in destroying spores as well as vegetative forms of patho- 

 genic species, for the resistance of eggs to it, for the readiness with which 

 the eggs are separated by it, and for the ease with which the disinfection 

 may be done. The solution consists of 5 gms. of the (commercial) 

 hydroxide added to 95 cc. of distilled water. Should eggs not settle 

 readily in it, slightly more water is added. This will not reduce the 

 absolute sodium hydroxide below 4%. 



Formaldehyde. The disinfecting efficiency of formaldehyde is gen- 

 erally known and eggs resist it well. Favorable results may be obtained 

 with a solution containing 6.25% formalin (approximately 2.570 form- 

 aldehyde). 



Mercuric Chloride. The following solution may be employed: 

 Mercuric chloride, 0.5 gm.; sodium chloride, 6 gm.; hydrochloric acid 

 (commercial), 1.25 cc; ethyl alcohol, 250 cc; and distilled water, 750 

 cc. If preferred the sodium chloride may be omitted. Mercuric chloride 

 of Y 2 the strength in the formula is followed by favorable results also. 



