October 20, 1893.] 



SCIENCE. 



217 



some future time. Adult Mycetophilid flies have been 

 collected by me on several occasions in parts of caves in 

 which my larvse were found, but it will be necessary to 

 "breed" the pupse and adults from the larvse before the 

 stages can be associated with certainty. 



"I have never seen your larva, but I have from a cave 

 in Jamaica, W. I., a Dipterous larva of similar form and 

 habits, except that it lies suspended free from the rock on 

 a thread of ropy slime-like material. I send you speci- 

 mens of this larva and also its pupa in alcohol, likewise 

 the imago which I bred from the pupa. You will see that 

 it is a Mycetophilid fly. No doubt you have noticed 

 similar flies in- fungi and particularly on coatings of fungi 

 under damp logs in dark woods. The larvse of these 

 fungus-inhabiting flies are similarly elongate creatures 

 and form thread-like tracks of slime across the surface of 

 the fungus. I have frequently observed that they can be 

 made to glide back and forth along this track precisely 

 in the manner of your cave larva, and that they can not 

 be induced to quit their hold upon the thread. The in- 

 teresting point to which I would like to call your atten- 

 tion is this. The silken thread of your Mammoth Cave 

 larva and the slime thread of my Jamaican larva as well as 

 the slime track of the fungus Mycetophilids may all be 

 similar products of the salivary organs and more or less 

 allied to true silk. The Jamaican cave fly makes a thread 

 ■ of six or eight inches in length fastened at both ends to 

 the rock on the underside of a ledge or stalactite, but 

 otherwise hanging freej and on this both larva and pupa 

 are found suspended as in a hammock. In the damp air 

 of the caves the thread never dries and hardens like 

 ordinary silk, but remains viscous and slime-like as in 



manner. Probable imagoes also found. (I subsequently 

 observed a pupa disclosing the fly and took specimens of 

 all the stages.)' " 



Fig. 4. 

 the case of other Mycetophilids. Nevertheless it pos- 

 sesses greater strength than an ordinary filament of 

 mucus and it occurs to me that it is nothing more or less 

 than a form of silk which does not lose its moisture and 

 become hard. I have read somewhere quite recently of a 

 process for the manufacture of artificial silk from a 

 collodion produced by the action of nitric acid upon palm 

 fibre. This silk remains moist until passed through 

 anhidrous ether, which removes the moisture and hardens 

 it. I would like much to know whether the silk thread 

 of your cave larva is not also somewhat viscous, and it 

 would be iateresting also to note the action of ether upon it. 

 "In the American Entomologist, Vol. III., p. 30, 1880, I 

 published a brief account of cave life in Jamaica. The 

 article refers to the fly as follows; 'A Mycetophilid fly is 

 found upon the stalactites, where its vermiform larva 

 may also be seen suspended by ropes of slime.' Referring 

 to my original field notes I find the following: 'Drunil- 

 ly, Parish of Trelauny, Jamaica, W. I., April 18th, 1877,— 

 among notes of examination of a large cave, much fre- 

 quented by bats and containing many tons of bat guano — 

 under ledges of stalagmite, long Dipterous larvas slung 

 in glutinous threads. Pupse also collected slung in same 



Explanation of the rtgures. 



Fig. I . A dorsal view of a Mycetophilid larva found under a 

 log. a, an outline of the head as seen from above. 



Fig. 2 . A web of one of the cave species. 



Fig. 3. A web-making cave larva, a, an enlarged side view of 

 the head. 



Fig. 4. The pupa of the larva represented in Fig. 3. 



SCAES ON APPLE TEEE TRUNKS. 



BY FRANK BOLLES, CAMBRIDGE, MASS. 



Old apple trees in New England are almost invariably 

 thickly dotted with round scars in their bark. Chains of 

 small holes seem at some more or less distant date to 

 have been bored in the trunks and larger limbs, but to 

 have healed without injury to the tree. I have seen trees 

 which bore thousands of these marks, arranged with 

 some appearance of regularity in rings encircling the 

 trunk and extending tier upon tier from a few inches 

 above the ground to a point much higher than a man's 

 head. In meetings of ornithologists I have heard many 

 of those best informed about birds' habits say that they 

 were unable to name the maker of these marks. Farmers 

 generally charge the Downy Woodj)ecker with doing the 

 work, and they often call him a Sapsucker in conse- 

 quence. Many people suppose that the holes were bored 

 a long time ago, and that they are not now made, hence 

 the impossibility of observing the bird while making 

 them. 



For several years I have kept close watch upon my old 

 orchard at Chocorua, N. H., hoping that I might catch 

 the little Sap-sippers at work. While my experience with 

 the Yellow-breasted Woodpeckers inclined me to suspect 

 them of being the birds concerned, I did not feel at all 

 sure that the Downy, who is so fond of stealing a drink 

 of sap from the drills of the Yellow-breasted, might not 

 have learned to do some boring on his own account. This 

 autumn I noticed half a dozen freshly made holes in a 

 very old apple tree. That proved clearly the continued 

 existence of the unknown worker. During September 

 both Downy Woodpeckers and the Sapsuckers were 

 abundant and very busy in my apple trees. The Downy 

 was fearless and honest in his manner. He was after in- 

 sects and he showed no shame and little timidity. The 

 Yellow-breasted Woodpeckers, on the other hand, were 

 very shy, and flew from a tree almost as soon as I came 

 within sight of it. This led me to watch them persistent- 

 ly, and at last, not long before I was called back to Cam- 

 bridge, I had the satisfaction of seeing one at work, drill- 

 ing and drinking. After making perfectly sure that he was 

 cutting new holes and drinking, I examined the holes 

 closely and satisfied myself that they were identical with 

 the kind so long in dispute. To wary Sphyropicus varius, 

 therefore, in his autumn migration, is to be assigned the 

 fretting of our old apple trunks. That he does all of this 

 work, I believe, but cannot, of course, affirm without 

 more evidence. 



A MISTAKE IN TEACHING BOTANY. 



BY B. EINK, FAYETTE, lA. 



Undeb the above caption I wish to enter a protest 

 against the method of teaching botany still in vogue in 

 certain colleges and high schools. If the error named 

 below prevails in any large University, it needs correc- 

 tion there as well. It exists in our village schools, and 

 will till the higher schools make a change for the better, 

 and send out teachers correctly trained in the subject. 



The mistake is the old plan of a spring term in botany 

 confined to a study of phanerogams, followed by the 

 analysis of from fifty to one hundred plants. This way 

 of studying botany came into use when the microscope 

 was scarcely known among the masses, and when the eco- 



