310 



PSYCHE. 



[Jnly— September iSSs. 



nomyia have only been found in the 

 throats of ccrt'/wn', those of the genera 

 Cephalomyia and Oestrus only in tylo- 

 poda and cavicornta, those of the 

 genus Gastropkihis in solidtmgnla 

 and iiiiiUinigitla {Rhinoceros), hut 

 JJypoderma, on the other hand, in 

 cavicornia {Bos, Capra, Anttlopc)^ 

 ccrvina {Cerviis, Moschus), and 

 equida, Ciiterebra larvae in rodeiitia 

 and j?iarsupiala, and finally those of 

 Derttiatobia in dogs, oxen, horses, and 

 even upon man. 



[p. 40] Another picture is formed 

 if the perfect insects are divided accuid- 

 ing to a peculiar character into those 

 with pectinate antennal bristles ( Ciite- 

 rebra, Dcrmatobia), and those with 

 naked antennal bristles {Hypodcrma, 

 Gastrophihis, Cephenomyia, Ccplialo- 

 mvid), since the larvae of the former 

 are parasitic in ungulate animals as well 

 as especiallv in rodeutia and viarsu- 

 pialia, but those of the latter only in 

 ungulata. This hitherto so convenient 

 and practical division likewise cannot 



be relied upon for an iufereuce. since 

 Oestries leporinus belongs to the gr(nip 

 of oestridae with naked bristle, but its 

 larva lives upon- a rodent. It is seen 

 that such divisions arc onlv artificial 

 and seive for orientation, but that 

 nevertheless nature cannot be farced 

 into their). Such divisions arc thercr 

 fore only temporary, and only too 

 often become untrue so soon as, new 

 discoveries are published. It is thercr 

 fore best to treat of the larvae accord- 

 ing to their genera, and- to limit tlieSe 

 as naturally as jiossible, since it has 

 thus far been found constantlv in this 

 family that the larvae of one .genus all 

 ha\'e a like life-histor-v, and conversely 

 the generic cliai'acters of the imagines 

 can scarcely lead us astray if we wish 

 to draw an inference as to the life- 

 history of a larva perhaps not yet inves- 

 tigated. In the case of a new genus, 

 however, we can infer its life-history 

 with very little certainty. Experience 

 alone teaches this. 



Waxy secretions of psvllid larvae. 

 Dr. Franz Low, in his "Beitriigezur kennlniss 

 der jugendstadien der psylliden" (Verliandl. 

 K.-k.zool.-bot. gesells., 1S84, v. 34; Abh.), p. 

 144, thus describes a curious secretion in the 

 larvae of Psyllu ulmi: "From wax-glands 

 surrounding the anus the larva emits a white 

 secretion, which appears as a hollow, vernii- 

 fprm thread that allows the passage through 

 it of the fluid excrement of the larva. This 

 white thread, which reveals the presence of the 

 larvae hidden in the axils of the leavesl^ehind 

 the stipules, elongates continouslv, but breaks 



off repeatedly on-account of its own weight and 

 consequently reaches no very considerable 

 length. Furthermore tliis larva secretes from 

 the wax-glands on the dorsal surface of tlve 

 last abdominal segment extremely fine white 

 threads, which form unitedly a very loose, 

 light flock." The larvae of Triozd, three spe- 

 cies of which larvae are described in the same 

 paper, have their entire outer margin sur- 

 rounded by hyaline, silky, very Jine, threads 

 of wax, which lie close to oiie another, and 

 seem to form a shorty closely-trimmed fringe 

 around them. 



