SECRETARY'S REPORT. 181 



mo?qiiitos. Otlicrs in these stages feed on tlie blood of living 

 animals, as the bot-flies and gad-flies ; many species subsist 

 entirely on toad-stools and other fungous plants ; many con- 

 struct galls on various annuals ; the blow-fly and others of that 

 class live upon putrifying animal matter ; the common house- 

 fly passes its preparatory stages in excrement; the Tachhiidm 

 glue their eggs on the skin of various caterpillars, and their 

 larvas enter and devour the juices of the animal, resembling 

 the ichneumon in their liabits ; some are said even to attack 

 and feed upon the eggs or bodies of spiders, the traditional 

 enemies of the race, thus consummating a species of poetic 

 retribution. The Hessian fly, the veheat-mi<Jge, the onion-fly 

 and others, are among the most noxious of insects. The black- 

 fly, Simxilium, the mosquito, Cnlex, the golden-eyed forest-flies, 

 C/iff/sops, the Tabanidfc, or horse-flies, and others, are the 

 cause of intense annoyance and irritation during the hot 

 months, to both men and animals. 



Among the flies that may be considered as beneficial to the 

 farmer, are the Bombyliidcc, or bee-flies, whose larvse are sup- 

 posed to be parasitic on certain vegetable-eating species, and 

 whose imagines subsist on the nectar of flowers, being furnished 

 with a long slender attenuated proboscis, adapted to sucking 

 liquids. Figure 55 (^Harr.') represents one of 

 this species, supposed by Dr. Harris to be the 

 Bombijlius ccqualis of Fabricius, or equal- 

 winged bee-fly, so called because the color of 

 the wings is nearly equally divided, one-half 

 being fuscous, the other hyaline. The body 

 of this fly is thickly covered with golden yellow hairs, which 

 are whiter beneath ; the figure represents it of the natural size. 



Laphria tlwracica of Fabricius, or the Laphria, (from the 

 Greek, meaning a forager, or robber, in allusion to its preda- 

 cious habits, or from Laphrius, an appellation of Mercury, on 

 account of its swiftness,) with a 

 yellow thorax, (figure 56, Harr.,') 

 is often seen in sunny clearings, 

 pouncing upon other insects, with a 

 deep hum, much like that of an 

 humble-bee, which the Laphrias 

 closely resemble in general appear- 

 ance. The species figured is of a ^'k- 56- 



