1899] ENTOMOLOGICAL SOCIETY. 25 



occasionally tinged with reddish brown, the feet black, che prologs blackish, the hairs 

 cinereous, blackish on the dorsal ridge, or a yellowish-brown with darker ridge. Occasion- 

 ally one is found when about half grown of a gamboge yellow, with a tinge of pink in it, 

 but these change before maturity to oae of the usual types. The principal appendages 

 are four pencils of black hairs, with white pencils below them on the thoracic segments, 

 two each on the second and third thoracic segments, and two black pencils on the eighth 

 abdominal segment. There is also a lateral white pencil on each side of the second 

 thoracic segment and some long hairs on the ninth abdominal one. In Harrisii, on the 

 contrary, the body and hairs are milk-white up to the last moult, the mature larva being 

 of a rather dingy brownish-yellowish shade, slightly darker on dorsal ridge. The head is 

 yellowish-brown, while the pencils, which are black in Tessellata, are orange in Harrisii, 

 except that there are no orange pencils on the posterior part of the body,- but only two 

 whitish ones projecting backwards on the eighth abdominal segment. The feet are 

 yellowish, tipped with red dish- brown, and the claspers whitish. Thirty-five years have now 

 elapsed, and yet the question as to whether these are distinct species or only interesting 

 varieties has not been definitely and satisfactorily settled, a fact by no means creditable 

 to North American lepidopterists. 



Some years ago I became interested in this question, and with a view to making 

 experiments imported and set out in our Mount Royal Park in Montreal a plane tree 

 (Platanus Occidentalis). It has now grown to be a fair-sized tree about 25 feet high, and 

 last year I began my experiments by securing the eggs of Tessellata. These in due time 

 hatched and were divided between several glass breeding jars, in one of which I had 

 leaves from my plane tree, and in the others oak, bass and other trees. I had no difficulty 

 except with those on the plane, but they refused to eat. Fearing they would starve 

 immediately I gave them an oak leaf for a start, and after they had had a meal or two 

 took it away and left them only the plane. This hunger forced them to partake of 

 sparingly, but they did not relish it, and the mortality was heavy. A number passed 

 first moult, but I only succeeded in carrying two past the second, after which they died. 



This year I appealed to Dr. Dyar to try to get me specimens of H. Harrisii, and he 

 and his assistant very kindly devoted part of a day to looking for them, but they were 

 only successful in finding four. These were sent me, but naturally I was not able to 

 make many experiments, and only found that while they preferred plane they would still 

 eat bass and elm. The laivse, are however, so very distinct from Tessellata that it seems 

 probable that the species is distinct in spite of the imagos being indistinguishable. I would 

 be inclined to lay down a law that where any two forms are certainly distinguishable in 

 any of their stages, and where the two forms are never found to breed, the one from the 

 other, or to occur in the same brood, they are entitled to rank as distinct species. 



The truth in regard to these particular forms ought to be easily investigated in any 

 locality where Harrisii occurs in moderate abundance. All that is necessary is to secure 

 a fair number of larvae, and when the moths are disclosed from the resulting cocoons to 

 mate them and then secure as many eggs as possible, preserving the parent moths and 

 keeping the batches of eggs separate. If under these circumstances the larvae were all of 

 the Harrisii type it would be fair to conclude that the form is a good species, though it 

 would be all the better if a further experiment were tried, viz., to see if Tessellata and 

 Harrisii would mate and produce fertile offspring with characteristics of both forms in 

 the preparatory stages. 



I have thus attempted to show the importance not only of the study of preparatory- 

 stages, but also of experimentation therewith, but there are many other and more practi- 

 cal subjects for study and experimentation than those to which I have alluded, such as 

 the possibility of propagating and disseminating bacterial diseases among caterpillars as a 

 means of checking the ravages of injurious species, and this leads me to direst attention 

 to the utter lack of all provision of facilities for the carrying on of such work at the 

 Central Experimental Farm. 



