THE CANADIAN ENTOMOLOGIST ISl 



(iri(iinall\ Iionic on I In- eighth, ninlli and tenth sl(;initcs respect ivel>', anri 

 lionioloiji/.cs theni with paired sl\li boiiic on the eightli, nintli and tenth stcr- 

 nili's of the niak- While ,d! ihri-e i)airs of st\li persist in the female (the pair 

 ()rit;inall\- borne on tlie tentli sternite niis^rating to a j)ositif)n on the ninth, in 

 the female), onK' the pair borne on the ninth sternite i)ersist in the male, the 

 other pairs gradualK' disappearing; as de\elopnient proceeds. 1( must be 

 admitted that Wheeler's choice of Xipliidium was an extrcmeh' unfortunate 

 one. sinct' the .m'nit.ilia of the m.des of these insects are too hij^hly modified to 

 i;i\(' the bi>st results for such an in\ i'stii;at ion ; and until the ontogenetic de\'elop- 

 nu'iit of more faxorable forms, such as the h'.phemerida, sawtlies, etc., have 

 been studied with a \ie\v to determining the interpretation of the parts in male 

 insects, we must conclude that the e\ idence available is not entirely satisfac- 

 tor>', especially since Heymons, Palmen, and others who ha\e also traced the 

 dexelopment of the parts in males of lower insects, do not agree with Wheeler 

 in man>- particulars. 



A study of the so-called gonopods, or arlhrostyles,* borne on the ninth 

 abdominal segment in trichopterous lar\ie, has convinced me that these struc- 

 tures form the claspers or gonopods of adult male caddice-flies (i. e., the struc- 

 tures labeled "c" and "b" in ¥\g. 2), and since these structures are evidently 

 appendages of the ninth abdominal segment (not of the tenth abdominal seg- 

 ment, as was stated in the article published in Psyche) in caddice-fly larvie, I 

 would interpret the outer claspers of the genitalia of the males of higher insects 

 .is ai:)jiendages (styli) of the ninth abtlominal segment. On the other hand, 

 the penis \al\es ma>' or ma>' not belong to the same segment, although I am 

 inclined to interpret them as appendages (endopodites ?) of the ninth abdominal 

 segment also. 



If the structures labeled "a" and "b" in Fig. 1 are homologous with those 

 labeled "a" and "1)" (with "c") in Fig. 5, and if these in turn are homologous 

 with the t^tructures labeled "a" and "b" (with "c") in Fig. 3, it is quite evident 

 that there has been a considerable sliifting of the parts in the different insects 

 under consideration. Thus, in the roach shown in Fig. 1, the styligers 

 or "coxites" labeled "a," instead of tending to remain more or less distinct as 

 in the Ephemerida ("a" of Figs. 4 and 5), become more closely united with the 

 ninth sternite "9^" of Fig. 1, while the penis valves "d" are apparently attached 

 behind the posterior border of the ninth sternite — which has either grown out 

 posteriorly beneath them, or the penis valves have been shifted forward basally. 

 Tf the structures bearing the label "d" in Fig. 1 are the homologues of the penis 

 \alves of the other insects figured, they have followed a line of specialization 

 leading toward the asymmetrical development of the parts, and their relation 

 to the styli or gonopods "a" and "b" is somewhat different from that occurring 

 in the higher insects. 



Another course of development has apparently been followed in the sawfly 

 shown in Fig. 3, since the ninth sternite "9*" (which does not project far pos- 

 teriorly in the ephemerid shown in Fig. 5, "9^") has grown outward and l)ack- 



*In the larvae of certain sawflies such as Ncurotomu, there occur near the base of the ster- 

 nite of the tenth abdominal segment, a pair of jointed appendages which I interpreted as seg- 

 mented stvli (arthrostyjes) from the fact that they are borne on the sternum of the segment. 

 Mr. Middleton, hov.exer, informs me that these apjjarent arthrcstyles are transformed into the 

 ccrci of the adult male insect, and if this l)e correct, the structures in (piestion should be desig- 

 nated as cerci rather than as styli (or artlirostyles) in these larvie. 



