CONTROLLED MATING IN HONEYBEES 



381 



use, except the last one, and in our own 

 laboratory. 



The artificial introduction of semen into 

 the reproductive tract of certain of the 

 warm blooded animals has been practiced 

 for a long time, and the principle is 

 scientifically sound. Prior to these 

 investigations, however, this principle 

 had never been successfully applied to 

 insects. Their small size presented a 

 baffling difficulty, but in the event that 

 the technique could be refined sufficiently, 

 the question still remained: does the 

 drone merely deposit the spermatozoa 

 within the oviduct of the queen, leaving 

 them to make their way as best they can 

 up the curving duct into the sperm reser- 

 voir, or does he reach farther and deliver 

 them under compression directly into the 

 spermatheca? The answer to this question 

 was established by the dissection and 

 examination of many naturally mated 

 queens as they returned to the hive after 

 the wedding flight. 



The office of the drone in mating appears 

 to be merely to deposit the tiny charge of 

 semen within the oviduct of the queen. 

 Immediately after this for the next four 

 to seven hours, and stimulated by some 

 force which is not fully understood, the 

 individual spermatozoa, numbering per- 

 haps a million or more, set up a powerful 

 lashing of their flagella by means of which 

 they work their way up the duct, and 

 collect at last in the spermatheca. 



A critically important item relating to 

 the physiology of copulation in honey- 

 bees should be mentioned here. Queens 

 freshly mated, as they return to the hive, 

 are observed always to bear in the genito- 

 anal vestibule a copious mass of mucus 

 from the accessory mucous glands of the 

 male. The function of this mucus is to 

 harden in contact with the air, and be a 

 sort of plug to close the vulva, preventing 

 the back flow of the semen, and protecting 



it from exposure to the air. It has been 

 established by repeated experiments that 

 if the mucous plug is torn away from a 

 normally mated queen, or even slightly 

 meddled with before she has borne it for 

 two or three hours, she may be tempor- 

 arily or permanently incapacitated to lay 

 fertile eggs. 



THE APPARATUS 



The insemination of a queenbee is by 

 nature a microscopic operation, and a 

 binocular microscope giving a magnifica- 

 tion of 15 to 18 diameters is indispensible. 

 An all-glass syringe convenient for hand- 

 ling the tiny bead of semen from a single 

 drone seems not to be made commercially 

 anywhere, and we are compelled to 

 design and construct our own. The 

 critical specifications of this syringe are 

 (1) a straight, all-glass plunger barrel of 

 perfectly uniform bore 0.5 millimeter in 

 inside diameter, and (z) a tight fitting 

 plunger controlled by a fine-threaded 

 screw allowing a plunger stroke of 15 to 

 zo millimeters. 



A consideration of first magnitude in 

 this work is that every movement shall 

 be under perfect control. To control and 

 stabilize the movements of the micro- 

 syringe, this instrument is clamped in the 

 jaws of a Barber pipette-holder (fig. z). 

 The turning of one or another of the three 

 nurled screwheads set at right angles to 

 each other in the three planes of space 

 slowly moves the syringe forwards and 

 backwards, up and down, right and left. 

 This micromanipulator is mounted on a 

 flange which rises from a false stage fitted 

 over the real stage of the microscope, and 

 is tilted so as to incline the syringe at an 

 angle of about 40 degrees to the horizontal, 

 thus permitting the operator to look into 

 the vestibule of the queen while emplacing 

 the syringe. 



The queen also must be securely held 



