102 



TEXT-BOOK OF ENTOMOLOGY 



FIG. 111. Fore 



tibia of Ph< tit /> it >t 

 carnifeu', cf, 

 showing no trace 

 of the tarsus. 



front tarsi are always absent in the males and present in the females. If 

 repeated mutilation has resulted in the entire disappearance of the tarsi in one 

 fossorial insect, it is reasonable to infer that the same results should follow in 

 a related insect in both sexes, if at all, and not in the male only. It is evident 

 that some other cause than inherited mutilation must be sought for to explain 

 the loss of the tarsi in these insects." (Proc. Amer. Phil. Soc., Philadelphia, 

 1889, pp. 529, 542.) 



The loss of tarsi may be due to disuse rather than to the inheri- 

 tance of mutilations. Judging by the enlarged fore tibiae, which 

 seem admirably adapted for digging, it would appear 

 as if tarsi, even more or less reduced, would be in the 

 way, and thus would be useless to the beetles in dig- 

 ging. Careful observations on the habits of these 

 beetles might throw light on this point. It may be 

 added that the fore tarsi in the more fossorial Cara- 

 bidse, such as Clivina and Scarites, as well as those of 

 the larva of Cicada and those of the mole crickets (Fig. 

 112), are more or less reduced ; there is a hypertrophy 

 of the tibiae and their spines. The shape of the 

 tibia in these insects, which are flattened with 

 several broad triangular spines, bears a strong resem- 

 blance to the nails or claws of the fossorial limbs of those mam- 

 mals which dig in hard soil, such as the armadillo, manis, aardvark, 

 and Echidna. The principle of 

 modification by disuse is well 

 illustrated in the following cases. 

 In many butterflies the fore 

 legs are small and shortened, and 

 of little use, and held pressed 

 against the breast. In the Lycse- 

 nidse the fore tarsi are without 

 claws ; in Erycinidae and Liby- 

 theidae the fore legs of the males 

 are shortened, but completely de- 

 veloped in the females, while in 

 the Nymphalidae the fore legs in 

 both sexes are shortened, consist- 

 ing in the males of one or two 

 joints, the claws being absent in 



the females. Among moths loss of the fore tarsi is less frequent. 



J. B. Smith * notices the lack of the fore tarsi in the male of a 



deltoid, Litognatha nubilifasciata (Fig. 113), while the hind feet of 



i Ent. Amer., v, p. 110, PI. II, Fig. 7. 



B 



FIG. 112. Fore leg of the mole-cricket: ^4, 

 B, inner, aspect ; e, ear-slit. After 



