OF \VASIII.\<;T<>\, VOLC.MI: \\i, ion 



country, and to be easily distinguished in the male, female and 

 larval stages. Several males were confined, one after the other, 

 with each female. Usually, when a male Uid'collix is introduced 

 into a jar with a female of its own species, matin"- occurs very quick- 

 ly, but with the females of this other species most of the male.- 

 failed to recognize the female, and only in a few instances dis- 

 played sexual excitement, which was of short duration except in 

 two cases. One of these males attempted copulation a few times 

 without success, while the other succeeded after many fruitle 

 attempts, but displayed great difficulty in disengaging himself 

 afterward. This female that had been fertilized laid eggs in due 

 time. The other was restless and abnormal in actions, but laid 

 three infertile eggs, and finally died. All the other females died 

 without laying eggs. Of the 48 eggs laid by the fertilized female, 

 many were infertile. In others the embryo developed but failed 

 to issue, and only ten larvae hatched. Of these most were very 

 badly deformed and unable to feed. Two of them, however, 

 fed and have lived fifteen months in confinement. They display 

 the specific characters of the male parent. It appears from tin- 

 above that in addition to the isolation of the two species by habit al 

 the species are separated by (l).lack of sexual attraction, (2) 

 mechanical difficulty in copulation, and (3) in some manner the 

 fertilization is faulty and results in gross abnormalities. The writer 

 believes that these two forms are very distinct species, but that 

 chance migration of the males may. very rarely, result in interspe- 

 cific unions, with a slight chance of the survival of hybrid offspring 

 which would naturally be reabsorbed in the local specie-; it' ii should 

 prove to be fertile. 



The question of sexual attraction even within a single specie 

 is in itself a very interesting and important question. We are. 

 of course, utterly unable to detect the difference in odors or other 

 factors by which one sex recognizes the opposite sex of its own 

 kind, and is stimulted to sexual excitement while with another 

 species the stimulus may be absent or repulsive. Some groups are 

 sexually mature as soon as they have hardened after issuance from 

 the pupa, and mate with their own brothers or sisters, but most 

 appear to have some obstacle (hat prevents breeding. The first 

 group are usually somewhat degraded and are inclined to form 

 numerous local races or color forms. An example of this group 

 is /-;/v>x hnnn-rnlix of which the following brief observation is sig- 

 nificant : 



From a colony of larva' found last spring (1913) in a rotten syca- 

 more log, the individuals were isolated in plaster cells where they 

 pupated and matured. The adults showed no desire for migra- 

 tion but lay quiet in the cells. A male was introduced into a cell 



