THE CHEESE SKIPPER AS A PEST IN CURED MEATS 11 



ning.' making short jumping flights, cleaning themselves, and engag- 

 ing in brief, vigorous sparring matches with other flies. In these 

 bouts the forelegs are used the most and are employed to seize and 

 shake the opponent. When not feeding, mating, or ovipositing the 

 flies may be found at rest, usually on a vertical surface. They may 

 be easily captured in a vial or killed with the hand. 



The ovipositor of the female is a three-jointed telescopic organ, 

 hyaline, with a black, slightly hairy, chitinized tactile tip. Some 

 chitmous reinforcing lines are present, these lines on the proximal 

 joint being sparsely hairy. The proximal joint of the extended ovi- 

 positor is twice as long as the other two combined, and the opening 

 of the tube is between the second joint and the tip or distal joint. 

 The abdomen of the female is pointed, that of the male blunt. 



The external reproductive organs of the male consist of a basal 

 knob bearing the copulatory claspers and a coiled filiform penis 

 nearly equal in length to the entire insect and coiled out of sight 

 beneath the right hand of the two dorsal asymmetrical scales which 

 protect the terminal segment of the insect. The penis is reinforced 

 with a hirsute black line of chitin, which chitinization, having a 

 permanent tendency to coil, seems to be the means whereby the 

 insect is enabled to return the organ to its serpentine position 

 beneath the dorsal scale. 



The mouth parts of the adult are similar in structure to those 

 of the house fly, the distal end of the proboscis being provided 

 with a perforated pad, of gridiron pattern, which functions as a 

 strainer. 



MATING 



Before the newly emerged female has assumed the adult form and 

 color, and often when she is but a soft transparent sac with wrinkled 

 wing pads, she is beset by the male flies. The act of mating, which is 

 consummated with great vigor, continues for a length of time which 

 is controlled by the temperature. Several records are given to illus- 

 trate this: In a number of trials at 65° F. pairs remained in copula 

 as follows: Two pairs 9% minutes, 1 pair 10 minutes, 1 pair 11 

 minutes, 1 pair 19 minutes. At 75° F. 2 pairs remained in copula 

 oy 2 minutes and other pairs, respectively, 6, 6, and 8 minutes. At 

 times, with room temperatures in the neighborhood of 90° F., the 

 mating impulse was markedly decreased. 



Mating takes place more than once in the case of pairs confined 

 in vials. Ovipositing females are not molested by the males, and are 

 sometimes observed in groups, apart from any males, depositing 

 eggs in masses. The act of mating is terminated by vigorous efforts 

 of the female, but in the case of old flies, with body fluids and 

 strength depleted, the separation often can not be made and in the 

 laboratory considerable numbers of confined flies die in copula. Of 

 1,353 flies which died when confined without water, 60 pairs and 

 3 trios (9.5 per cent) met death in this condition. Microscopic 

 examination of the trios showed that in each case two males were 

 actually in copula with a single female. It is not probable that 

 death in copula often precedes oviposition, but the writer has ob- 

 served its occurrence. 



