April, 1904.] Galls and Insects Producing Them. 127 



were found (Figs. 107, 108). A careful study of the mouth- 

 parts lead me to consider No. 107 as a true gallmaker and No. 

 108 as a j)arasite. The mouthparts of the one which I consider 

 a true gallmaker were as strong as those of C. petiolicola (Fig. 

 103). The mandibles of the parasite (108) were equally strong 

 and showed what appeared to be rudimentar}^ gland structures. 



Holcaspis globulus Fitch was the only bud (i. e., incipient 

 stem gall, Part III, Fig. 34) gall examined. In the young larvae 

 the mouthparts are weak, but as the larvae approach maturity 

 the mandibles become very strong (Fig. 109) and well fitted to 

 cut the opening for the escape of the insect. However, the 

 mouthparts were not so strong as in the case of C. petiolicola, but 

 the gall of H. globulus is not so dense as the gall of C. petiolicola. 



The mouthparts of Nematus pomum Walsh (Fig. no) were 

 ver}' similar to those of the Cynipidae. I am not inclined to con- 

 sider the apparently glandular-like structure observed in a few 

 species of any great importance. They may be suctorial or they 

 may be degenerate organs. I consider the stimulus as purely 

 mechanical. The character of the gall may depend iipon the 

 location, which would result in difference in tension in different 

 parts of the plant on which the gall may be located and also upon 

 the laws of natural selection, which will be considered in the latter 

 part of this paper. 



It would be interesting to know the exact time that cell divi- 

 sion begins in the formation of a gall, but it is very difficult to 

 make satisfactor}^ observations upon this point. Adler has made 

 successful observations upon this stage in Neuroterus laviuscultis 

 and Biorhiza aptera. He says: "The moment the larva has 

 broken through the egg covering and has for the first time 

 wounded the surrounding cells with its delicate mandibles, a 

 rapid growth begins. This goes on so quickly that while the 

 posterior part of the larva is still within the covering a wall of 

 like growth of cells has already arisen in front. This rapid cell 

 increase can be easily explained because the irritation set up by 

 the emerging larva is exerted upon highlj- formative cells which 

 collectivel}- possess ever)?- condition of growth. The cells which 

 are primarily around the larva cannot be distinguished from the 

 parenchymatous cells from which the)' proceed." 



4. LEPIDOPTKRA. 



A careful study was made of the mouthparts of the Gelechia 

 solidaginis Fitch (Fig. in) and upon an undetermined species 

 found upon Rudbeckia laciniata (Part VI). The mandibles are 

 larger and much stronger than in an}' of the Hymenopterous 

 gallmakers which I examined. The gall is also much stronger 

 than any of the Hymenopterous galls whose larvae were studied. 

 No glandular structures were observed. 



