248 INSECTA. 



four feet are even entirely free to their origin, where they 

 merely adhere to their respective segments by a median or 

 sternal line. The last two or three rings are without feet. 

 A series of pores is observed on each side of the body, 

 which were considered as stigmata, but, according to Savi, 

 they are simply designed to afford a passage to an acid fluid 

 of an extremely disagreeable odour, which appears to serve 

 as a means of defence; the respiratory apertures, for whose 

 discovery we are indebted to him, are situated on the sternal 

 part of each segment, and communicate internally with a dou- 

 ble series of pneumatic sacs strung together like a rosary, ex- 

 tending along the body, from which proceed tracheal branches 

 that ramify over the other organs. According to an observa- 

 tion of Straus, the sacs or vesicular trachea are not, as usual, 

 connected with each other by a principal trachea. 



In the environs of Pisa, where M. Savi collected the pre- 

 ceding facts, the nuptial season of the common lulus com- 

 mences near the end of December, and terminates about the 

 middle of May. The male organs of copulation, in this spe- 

 cies, are situated under the sixth segment, but they do not 

 appear in this form till the individual has attained the one- 

 third of its full size; until this epoch, that place is occupied 

 by a pair of feet (the fifteenth), which is always found there 

 in the females ; in the latter, the orifice of the sexual organs 

 is between the first and second segment. Some female Glo- 

 meres and luli, behind the origin of the second pair of feet, 

 exhibit two convex mammillae, which appear to characterize 

 this sex ; that of the males also consists of two mammillae, but 

 each of them is terminated by a scaly and twisted hook. 

 These Insects, in coitu, erect the anterior extremities of their 

 bodies, and place them in contact, face to face, twining round 

 each other inferiorly. The body of the new-born animal is 

 reniform, perfectly smooth, and destitute of appendages. 

 Eighteen days after, it undergoes its first change, and then for 

 the first time assumes the form of the adult, still, however, 

 having but twenty- two segments ; the total number of feet 

 also amounts to twenty-six pairs. Savi appears to contradict 



