tion or disability of the specimens raised in northern climes to 

 propagate. This is another proof of the frequency of such inva- 

 sions, as each colony of larvae is the product of an imigrated 

 female, not of a female born in the northern region. 



Modern investigations have also demonstrated tha.t Ac/ieron- 

 tia Atropos and DcilepJiila Celerio do not propagate in Europe, 

 and, consequently cannot be considered as indigenous species. 



A French gentleman in San Francisco has shown me a little 

 collection of insects, caught on board a vessel after a heavy 

 gale, fifty-four geographic miles from the coast of Brazil. All 

 these insects were Sphinges. They were ten in number ; five 

 Macrosila Cingidata, three PJiilainpehis JiissieucE and two speci- 

 mens of a CJicErocmnpa. 



I could quote here a great many other instances that prove 

 the wonderful powers of flight of these insects and their disposi- 

 tion to make use of them, but I consider the different facts men- 

 tioned here sufficient to demonstrate the impossibility to take 

 measures against an invasion of such enemies. At the same time 

 such measures, even if successful, would do very little good, be- 

 cause, in the few cases, where these insects inflict perceptible 

 harm, the harm is but transitory, the enemy taking leave as ab- 

 ruptly as he appeared unexpectedly. 



The advice to catch and kill the Sphinges hovering over 

 flowers is as impracticable as to divert the course of a river by 

 palling. But if some people, not minding practical advantages, only 

 wish to get even with the uninvited guests, let them plant PJiysian- 

 thiis, and the torn off trunks sticking out of the flowers will satisfy 

 the most revengeful disposition. 



We would expect that the eminent power of flight in this 

 group would produce a considerable number of cosmopolitan 

 species, but there are comparatively but few. Two courses com- 

 bine to restrict the majority to local distribution. 



I. Their larvae never are truly polyphagous. Most of them 

 feed exclusively on a genus, many are even restricted to a single 

 species whose geographical limits, of course, must comprise in 

 that case the geographical limits of the Sphinx. The adapta- 

 bility of their larvae to the other kinds of food generally does not 

 pass the limits of the botanical family, frequently, as mentioned 

 above, does not extend even to species of the same genus. So 

 Dcilephila Euphoj-biw lives in quantities on Ei/phurbia Esii/a, rarely 

 on E. Cyparissias and even in captivity it scarcely can be pre- 

 vailed upon to feed on any other species and rather will die than 

 touch most of the species of the Genus Euphorbia. 



Its congener D. Lineata possesses of all the Sphinges known 

 to me the greatest powers of adaptation. Onagraceiv, RubiacecB 

 VitacecB, Poi'tulacacecB and Polygonaccce will serve as food for its 

 larva. 



In consequence this species is to a considerable extent cos- 



