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SCIENCE 



[N. S. Vol. XLII. No. 1077 



the maggot remains quiescent therein exposed 

 to the conditions of the open for more or less 

 time after the act of oviposition. The high 

 viscosity of the caudal end of the chorion indi- 

 cates that the egg is firmly attached hy that 

 end to some surface, where it remains perma- 

 nently. The high fecundity indicates a high 

 mortality of the first-stage maggot, a reduced 

 chance of reaching the host, and hence pre- 

 supposes that the egg is not deposited on the 

 host nor on any object that will be certain to 

 come in contact with the host. The operculum 

 at cephalic end indicates that the maggot, on 

 being awakened from its quiescent state, imme- 

 diately escapes by that exit. A normal excite- 

 ment of the maggot to activity can be induced 

 only by the heat resulting from close contact 

 with the body of a warm-blooded host animal. 



As far as Cuterebra is concerned, we can feel 

 quite confident that its host relation is main- 

 tained through stealth, and that, barring acci- 

 dents, the fly never comes in contact with the 

 host. The eggs are probably deposited in the 

 burrows or runways of the rabbits, rats and 

 other small mammals which it parasitizes. I 

 have found these flies in considerable num- 

 bers in the southwestern mountain regions of 

 North America, where they uniformly either 

 perch on dead twigs beside a stream or sit on 

 rocks near the running water or on the earth 

 banks of streams. They evidently take such 

 stations in order to observe the movements of 

 rodents, with a view to locating favorable 

 places for oviposition. Their small antennae 

 indicate a poor sense of smell, while their large 

 and finely-facetted eye-surface indicates good 

 sight. 



Dermatobia parasitizes not only man, but 

 many of the larger mammals. Such animals 

 do not live in burrows or frequent regular run- 

 ways or places of concealment. Thus Derma- 

 tobia can not hope to reach its hosts by em- 

 ploying the methods of Cuterebra. It has a 

 much smaller fecundity, less than eight hun- 

 dred according to Neiva of Brazil, which indi- 

 cates that it adopts some method much more 

 apt than that of Cuterebra to connect with the 

 host. Its maggots are very common in cattle, 

 dogs and man in South and Central America, 



yet among the natives no one seems able to 

 identify the fly that deposits the egg. The 

 indigenes of South America accuse a variety 

 of dipterous insects of mothering these mag- 

 gots. 



Within the past decade, observers in Central 

 and South America have discovered a number 

 of instances of mosquitoes, uniformly of the 

 genus Janthinosoma, bearing a cluster of 

 Dermatobia eggs attached by their ends to the 

 under surface of the body. Apparently the 

 credit for the first discovery of this kind be- 

 longs to Mr. F. W. Urich, government ento- 

 mologist of Trinidad, who sent one of these 

 egg-laden mosquitoes to Washington in 1905. 

 The importance of the matter was not sus- 

 pected at the time, and the specimen can not 

 now be found. More recently Gonzales-Ein- 

 cones observed the same thing in Venezuela, 

 and inferred that the eggs were originally de- 

 posited on the leaves of plants frequented by 

 the Janthinosoma, which gathered them up 

 while walking about. His observations and 

 conclusions were published and endorsed by 

 Surcouf, of Paris. 



In the absence of information to the con- 

 trary, we are justified in supposing that Derma- 

 tobia has a reproductive system and egg much 

 on the same practical order as those of 

 Cuterebra. Being unable to maintain its host 

 relation in the same manner as Cuterebra, and 

 being similarly unable to approach its hosts 

 without unduly alarming them, since both flies 

 are heavy-bodied and noisy in flight, it must 

 necessarily resort to some extraordinary de- 

 vice for accomplishing its purpose. 



Judging from the accounts of both natives 

 and foreigners who have been infested with 

 Dermatobia maggots, several distinct species of 

 blood-sucking diptera may be employed by the 

 fly for carrying its eggs. Mr. J. C. Crawford, 

 of the U. S. National Museum, during a stay 

 in Costa Rica, was actually bitten by some fly, 

 and a Dermatobia maggot resulted at the point 

 of biting. He also relates a case of an Amer- 

 ican in that country who stated positively that 

 a yellow fly annoyed him in numbers on one 

 occasion, crawling beneath his clothing. After- 

 ward some two dozen Dermatobia maggots 



