EGG- PLANTING APPARATUS 



Newly hatched boll weevil larvae are cannibalistic and thus have to be separated 

 for placement in the larval diet medium so that they will not contact each other. Since 

 larvae are legless, they cannot cling to the agar-base medium in order to bite off 

 pieces from its smooth surface. The larvae must be placed on a rough surface so that 

 they can push the dorsal surface of their thoraxes against the medium and thus obtain 

 sufficient leverage to force their mandibles into the medium. Workers have satisfied 

 the requirements of the larvae by placing them in individual holes punched in the medium. 

 Vanderzant and DavichM/ and Earle et al.li/ used small shell vials partially filled with 

 larval medium. One egg was placed in each vial in a small hole punched in the medium. 

 Brazzel et al.— ^ used petri dishes containing larval medium punched with 50 holes to 

 receive the eggs. For both types of rearing equipment, the eggs were picked up individ- 

 ually on a sable-hair brush or dissecting needle and placed in the holes in the medium. 

 An experienced technician could plant from 500 to 600 eggs per hour in either of these 

 ways. 



Because the planting of as many as 20, 000 eggs a day entailed large labor costs, 

 a less costly method was sought. The methods tried included mixing the eggs with 

 granulated, moist diet medium; mixing them with dry medium to which water was later 

 added; and suspending them in different solutions applied so as to flood the surface of the 

 medium. None of these methods proved successful. A machine was then constructed to 

 aid in planting the eggs . 



The basic unit of the machine (fig. 5) consisted of a circular brass chamber (K), 

 3 inches in diameter and 1 inch in height, with a top and bottom plate. Evenly spaced 

 holes were drilled in the bottom plate of the chamber. Into these holes seventy-eight 

 23-gauge, stainless-steel hypodermic needles (L) were inserted so that they extended 

 one-half inch above and below this plate. The needles were then soldered in place. All 

 needles were ground to exactly the same length and the ends flattened. Three adjustable 

 legs (M) were fastened to the sides of the chamber so that when the legs were resting on 

 a flat surface, the ends of all the needles were 0. 8 mm. above the surface. Two 5- inch 

 copper tubes (N) were soldered to the top plate of the chamber, with one of the tubes 

 extending inside the chamber within 1 mm. of the bottom plate. Rubber tubing, 

 connected to the copper tube extending inside the chamber, was in turn connected to a 

 vacuum source. The other copper tube was similarly connected to a compressed-air 

 source. 



Two microswitches (O), also mounted on the chamber, allowed the operator to 

 turn them on and off with his fingertips while holding the chamber in his hand. One 



10/ See footnote 2. 

 11 / See footnote 4. 



12/ Brazzel, J. R. , Davich, T. B. , and Raven, Klaus. Rearing the boll weevil 

 on an artificial diet. Tex. Agr. Expt. Sta. Misc. Pub. 353, 4 pp. 1959. 



