322 



Pupa (PI. LXXX, Fig. 7). — Length, 5-7 mm. Pale yellowish 

 brown, opaque. Head with two short hairs on upper anterior margin. 

 Prothoracic respiratory organs short and stout, situated well forward. 

 Integument of entire pupa with microscopic reticulations. Thorax with 

 numerous short hairs or spinules arranged as shown in figure. Abdo- 

 men with numerous stout spinules or small thorns as shown in figure, 

 the dorsal arrangement of which is as shown in Figure 9, as is also the 

 apical armature of abdomen ; spiracles not distinguishable. 



Larvae of this species were abundant on tree trunks, where through 

 injury the sap was exuding, at Urbana, in July, August, and Septem- 

 ber, 191 5. Many imagines were reared from larvse obtained from the 

 trunk of a mulberry tree, and on the campus of the LTniversity of Illi- 

 nois there were several elm trees on which the larvae were common. In 

 the case of all trees upon which I found the species it is noteworthy 

 that there was a fungous growth over the surface where the exuda- 

 tion occurred, and in this the larvae moved with considerable facility. 

 They bear a striking resemblance to the larvae of aquatic Ceratopogo- 

 nincc and progress by the same selrpentine motion as do those larvae. The 

 larval skin is not generally entirely freed from the pupa at transforma- 

 tion, the apical half of the pupal abdomen being enclosed in it, the head 

 of the larva lying close to the ventral surface of the abdomen. The 

 pupa, just before the emergence of the imago, makes its appearance at 

 the surface of the matter in which it is buried, having been previously 

 visible only through the presence of the small respiratory organs, 

 which generally pierce the upper layer of the covering. I found that 

 the pupae when removed from their normal position in the semi-liquid 

 matter can regain that position by means of a rotary motion of the 

 i)ody, entering, tail first, until all but the apices of the thoracic respira- 

 tory organs are enveloped. LTnder natural conditions they pupate un- 

 der the loose bark and possibly in this way cause very slight injury. 



No damage is done to the trees by the presence of the larvae so far 

 as I can discover, and they are present only in those trees where an 

 injury causes an exudation of sap. It is not impossible that they may 

 have an irritating effect upon the wound other than that suggested 

 above, but I doubt it. They feed upon the liquid exudation and not 

 upon the fiber of the tree, and I reared many examples after the larvse 

 had been removed from the trees for over a month, their only food 

 being that provided by the fungous matter collected along with them. 

 I have observed that the first cold weather, not frost, proves fatal to 

 most of the larvae. 



Of parasites I found only a small worm which moved freely about 

 in the interior of the body of the larva. In form this resembles a 



