464 Phylum Arthropoda 



which are reduced to indistinct elevations in the male. (Fig. 80.) 



The pupae hatch into small, brownish beetles having a mean length, 



according to Brindley (1930) of 3.4 mm., mean width across the thorax 



of 1.02 mm., mean male weight of 1.48 mg., and mean female weight 



of 1.78 mg. Although adult 

 Tribolium may live two or three 

 years it is probable that their usual 

 life span runs from six months to a 

 year. The time required from 

 oviposition to emergence of the 

 imago varies with the ecological 

 conditions. At 28 C, 75% rel- 

 A/a/e Fema/e ative humidity and in whole wheat 



Fig. 80.— Terminal view of male and fe- fl our> Chapman and Baird (1033) 

 male Tribolium pupae showing sexual char- r j ,. , . , 



acteristics. (From the Quart. Rev. Biol., foUnd . that metamorphosis took 



with permission.) approximately 40 days. 



Tribolium lives in many types of 

 grain and grain-like habitats. It has been reported from whole wheat 

 flour, patent flour, patent breakfast cereals, bran, rice flour, rye flour, 

 corn meal, barley flour, oat meal, chocolate, spices, certain nuts, and 

 sometimes as predacious on specimens in insect collections. The re- 

 quirements of the investigator, however, usually rule out most of these 

 substances as suitable culture media. Here, it is necessary to have a 

 medium which may be passed through a sieve fine enough to separate 

 eggs, larvae, pupae, and imagos from the flour and still be nutritious 

 enough to sustain the population. At the present moment it is impossible 

 to state what type of medium best fulfils these requirements. Chapman, 

 who first developed an experimental culture technique for Tribolium, 

 has used finely ground whole wheat flour. Park has used an unbleached 

 patent flour (Ceresota). Either may be recommended at this time. 

 Of course, if the culturist is not interested in obtaining the smaller 

 stages of the beetle (eggs and early instar larvae) for study and count, 

 whole wheat flour, with the bran left in, will make an excellent medium. 

 The following specific program in developing and maintaining Tri- 

 bolium stock cultures may be suggested as a working scheme. 



1. Into each of a number (depending on the stock desired) of pint milk 

 bottles put about 200 gm. of whole wheat or patent flour. 



2. To each bottle add 10 males and 10 females and stopper with a 

 cotton plug. 



3. Place in an incubator or a constant temperature room with the 

 temperature at 28°C. The humidity may be allowed to vary between 

 25% and 75% or may be controlled. These beetles may be reared at room 

 temperature but it is preferable to culture them in an incubator. 



4. The bottles should be examined by sifting (method to be described 



