30 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



"I. humilis belongs to a small group of neotropical species embrac- 

 ing also I. iniquus Mayr, dispertitus Forel, keiteli Forel and melleus 

 "Wheeler. The workers of keiteli and melleus may be at once distin- 

 guished by their color, the former having a yellowish brown head 

 and thorax and the remaining parts brownish yellow ; the latter being 

 pale yellow with a blackish gaster and funiculus. In these and in 

 I. iniquus and dispertitus the mesoepinotal constriction is much deeper 

 than in humilis and the meso- and epinotum are of a different shape. 

 The mesonotum in profile does not form a continuous, even line with 

 the pronotum and the epinotum is very protuberant and almost coni- 

 cal. /. liumilis represents a transition from the above group of 

 species to that of I. analis Em. Andre, which is very common in the 

 Southern States. This species has a shorter, more robust thorax, more 

 like that of Tapinoma, and much less constricted in the mesoepinotal 

 region. 



' ' The above description was drawn from a number of workers, males 

 and females taken from the same nest in Baton Rouge, La., by Mr. 

 Wilmon Newell. The types described by Mayr were captured by 

 Prof. P. de Strobel in the environs of Buenos Ayres." 



An interesting point concerning the males, is that in certain colonies 

 they occur in great abundance. This was first discovered by one of 

 my assistants, Mr. G. A. Runner, who in December of 1907 found a 

 colony in which the winged males were almost as abundant as the 

 workers. Many other colonies which have been under constant obser- 

 vation for the past five months have not contained males at any time 

 during that period. Prof. Wheeler has suggested that doubtless the 

 appearance of a great many males in certain colonies is accounted for 

 by the presence of egg-laying workers therein. 



The Egg. — The egg deposited by the queen is elliptical, pearly 

 white and without markings. As the time approaches for it to hatch 

 it becomes duller in appearance but does not perceptibly change color. 



The average size of the egg is .3 mm. long by .2 mm. wide. 



The largest egg encountered while measuring a series was .34 mm. 

 long by ,24 mm. wide, and the smallest .27 mm. by .187 mm. 



The rate of egg deposition has not been determined, but one queen 

 under observation in a cage deposited at the rate of 30 eggs per day, 

 now and then suspending oviposition for several days at a time. 



The incubation period of the eggs in a glass cage in the laboratory 

 extended from Oct. 1st to Nov. 15th, a period of 45 days, during 

 which time the maximum temperature was 87° and the minimum 29°, 

 with an average daily mean of 63°. Calculating the effective tem- 

 perature from 43° F. and the actual mean for each day we find that 

 941 degrees of effective temperature were required for the develop- 



