AQUATIC MIDGES AND SOME RELATED INSECTS. 41 



allowed to go uninjured. One of these crustaceans was killed and placed near the head 

 of the hungry larva, but it was left undisturbed until movement was imparted to it by 

 the aid of a needle. From repeated observations it seems apparent thac the larvae of 

 this subfamily will not touch anything which is not moving. When movement was 

 imparted artificially to dead pyschodid larvae they were attacked, but before the skin 

 was broken the larva abandoned them. When tried a day or so later on this larva it 

 would not touch it, thus showing that decaying or dead material is not eaten even 

 when the larva is very hungry, a fact in decided contrast with the behavior of a number 

 of Chironomus larvae, especially Chironomus lobiferus. The Tanypus larva to which 

 was offered a freshly killed crustacean, however, ate it readily. It nevertheless showed 

 a preference for small recently hatched bloodworms. These were swallowed whole and 

 were apparently uninjured, as they were capable of moving for a time after being 

 swallowed. 



The method of attack and the defensive attitude of the larvae of this subfamily 

 were well shown in an encounter which occurred between two larvae which the author 

 was keeping on short rations preparatory to making observations on their feeding 

 habits. The larvae were of different species, one having a smaller and longer head than 

 the other. The encounter was a head-on collision, each apparently striving to defend 

 itself. They were taken under the compound microscope and their behavior observed. 

 The head of the smaller larva was apparently not much within that of the larger one, but 

 it was easy to see that the muscles within its head were being sucked toward the anterior 

 tip of the head. The result was that the smaller larva was killed, although it was not 

 consumed nor were any of the muscles of the head actually sucked out. The survivor, 

 although unprovided with food from any other source, left its victim undisturbed as a 

 result, doubtless, of its lack of movement. 



An observation on Tanypus carneus well illustrates the function of the head as a 

 sucking organ. A specimen that had been without food for four or five days was placed 

 in a watch glass with a very active bloodworm (Chironomus sp. ?) which was about the 

 same size as the Tanypus larva. The Tanypus larva attacked the bloodworm just back 

 of the head, employing its sharp mandibles to hold the larva. Very soon a reddish color 

 could be observed in the head of the attacking larva, showing that it was beginning to 

 suck the blood of the other. Then the alimentary canal was cut off, probably by the 

 mandibles, and with its contents (diatoms, etc.) sucked into the body of the Tanypus. 

 This left only the collapsed body wall of the larva to be consumed. This was accom- 

 plished by the use of the same powerful sucking apparatus. The body wall was drawn 

 into the mouth while the hypopharynx rasped a hole through it, then the continued 

 squeezing and sucking action of the head removed the muscles of the body wall. This 

 method of treatment was repeated on different parts of the body until finally all the 

 muscles of the body wall were removed. In this case the head was not swallowed and 

 the muscle fragments of the bloodworm were in such a broken state that they would 

 almost defy identification. 



Miall and Hammond have remarked on the presence of red coloring matter in the 

 body of Tanypus larvae which they consider due to the bloodworms they have eaten. 

 It is easy to confuse a natural red color with the color due to the food eaten, but a little 

 experience will enable one to see a difference in the intensity of the color that is unmis- 

 takable. 



