BUCKINGHAM. — DIVISION OF LABOR AMONG ANTS. 437 



8. But in each of these characteristics there is. a graded series, so 

 that a distinction into classes cannot be made ; indeed, it sometimes 

 happens that in a single individual of the middle size some characters 

 more clearly resemble those of the large workers, while others are more 

 like those of the small. These observations tend strongly to confirm 

 those made by measurements on Camponotus americaniis. They are, so 

 far as I am aware, the only observations of the sort made on this genus. 



In order to see how much the queens (Plate, Figure 1) of Camponotus 

 pictus differed from the tvorkers in regard to these same structures, I 

 made similar observations on them, comparing them with the largest 

 ■workers, which it is evident they more closely resemble than they do 

 the small ones. The results follow: 



1. The head of the queen is here somewhat, though not much, 

 larger than it is in the largest worker. In regard to its shape, as com- 

 pared with that of the worker, it is only slightly broader in proportion 

 to its length, about as much as we should expect irom its increased 

 size. The posterior margin of the head of the queen resembles very 

 closely that of the largest worker. The dorso-ventral axis of the head 

 is slightly shorter than in that of the worker. 



2. The length of the antennae, in proportion to the size of the head, 

 is less in the queen. The antennal joints are of the same number in 

 worker and queen. If the length of the scape is compared to the width 

 of the head, it is found that in the queen it is hardly, if any, shorter 

 than in the large worker. The funiculus of the queen is slightly 

 shorter in proportion to the length of the scape. In proportion to the 

 size of the head it is also somewhat shorter, being actually of about the 

 same length in both forms. The scape in the queen is still thicker at 

 the distal end than in the large workers. 



3. The compound eyes are slightly further back than in the large 

 worker, and resemble the condition in the small worker more closely in 

 being a little nearer the margin than in the large worker. 



4. The clypeus is even flatter in the queen than in the large worker 

 and slightly more indented by the cheeks ; the arch is curved in both. 



5. The frontal carinae are slightly further apart in the queen than 

 in the large worker. 



6. The mandibles of the queen very closely resemble those of the 

 large worker. 



So far, these characters make it appear as though the queen 

 were merely at one end of a long series of females. But in this 

 species other characters, such as the more developed ovaries, the pres- 

 ence of wings, etc., show that there is a noticeable break between the 

 queen and the largest worker. 



