THE AMEEICAN ENTOMOLOGIST. 



47 



Sawfly, and the legless larva of the iutniding 

 Snout-bcetle, we shall often find in July in the 

 Willow-apple galls a small lively wriggling 16- 

 legged caterpillar, cross-barred with alternate 

 bauds of brown-black and milk white, so as to 

 present quite a harlequin-like appearance. This 

 is another intruder or Guest upon the tenement 

 which rightfully appertains to the Sawfly larva; 

 and it behaves in the same outrageous manner 

 as the Snout-beetlc larva, for it is mean and 

 selfish enough to murder its Host either before 

 that Host is born or shortly after he is born. In 

 the May of the succeeding year this pretty 

 banded larva, after having passed through the 

 usual pupal stage, emerges in the form of a 

 small dull-gray moth, with very narrow elon- 

 gate wings, known as the Willow-apple Tinea 

 (Brttrachedra salicipomonclla, Clemens) ; and 

 the female moth, after coupling, is then ready 

 to operate upon another crop of Willow-apple 

 galls, and destroy through the instrumentality 

 of its reckless and unprincipled olTspring a sec- 

 ond generation of poor honest hard-working 

 Sawfly larvae. This very same moth we have 

 also bred from two perfectly distinct Willow- 

 galls {8. desmoiUoides, Walsh, and S. rhodoides, 

 Walsh), both of which grow on the Humble 

 Willow, and the first of which produces a Saw- 

 fly while the second produces a Gall-gnat. 

 Hence, precisely in the same manner as we 

 proved that the Sycophant Curculio must be a 

 Guest and not a Gall-maker, we may prove 

 the same thing of the Willow-apple Tinea. 



In our first Article on "Galls and their Arch- 

 itects," speaking of the dift'erent Guest-insects 

 that are found in galls, we stated (page 109) 

 that some of them were very closely allied to 

 the gall-maker, and some were as difierent as it 

 is possible to conceive. The two Guest-larvae 

 that we have already referred to, as found in 

 profusion in the Willow-apple Gall, belong to 

 the latter group ; for while the larva of the Wil- 

 low-apple Sawfly is 20-legged, that of the Syco- 

 j^hant Curculio is entirely legless, and that of 

 the Willow-apple Tinea is IG-legged; and both 

 of these last produce winged insects, which are 

 as different from the Sawfly as a Hawk is from 

 a Pigeon. There is still a third Guest-insect 

 which infests this gall ; but this, instead of being 

 widely distinct in all its stages from the true 

 gall-maker, actually belongs to the same genus 

 {JSTematus) and is of about the same size, though 

 its general color is pale grass-green instead of 

 honey-yellow, and its dark markings are much 

 fewer in number and are very difTorently ar- 

 ranged. This is the Beggar Sawfly (jVematus 

 mcndicus, Walsh) ; and what we took to be its 



larvas were 20-legged like the true gall-makers, 

 but differed from these last in being of a pale 

 ash-color with some pale dusky markings on 

 the body, instead of pale greenish-white with 

 no dark markings at all on the body. Wc also 

 bred another specimen of this same Beggar 

 Sawfly from the same Willow-cabbage gall 

 (.v. bvassicoides, Walsh), that we figured in the 

 First Volume of our Magazine (page 105, Fig. 

 84). Now, this last gall is the work, not of a 

 Sawfly, but of a Gall-gnat; so that it follows— 

 as in the case of the Willow Tinea and in sev- 

 eral other instances which we have pnt on 

 record — -that the very same Guest-insect some- 

 times infests galls made by insects belong- 

 ing to the most widely distinct Orders. Of 

 course, it further follows from the fact just 

 stated — asinthecaSo of .our other two Guest- 

 insects— that this Beggar Sawfly, being bred 

 from widely distinct galls, cannot be a gall- 

 maker; and as no known Sawfly is parasitic in 

 its habits, it cannot be a Parasite, and must con- 

 sequently be a true Guest in both the galls 

 which it is known to inhabit. 



Besides the above three Guest-insects, there 

 are several Parasites which we have bred from 

 the Willow-apple gall, some of which appear 

 to infest the architect of the gall, while others 

 attack the Guest-insects. But, as our readers 

 are by this time tolerably familiar with the 

 mode in which Parasites attack the various 

 kinds of plant-feeding insects, and as there is 

 nothing at all remarkable in the mode in which 

 these particular parasites operate, we will not 

 occupy unnecessarily the space, which we have 

 to devote to the history of our different Gall- 

 insects, by dwelling further upon this stale 

 subject. 



Let us now pause for a moment and consider 

 how complicated is the great tangled web, in 

 which evei'y Animal organism is enveloped, as 

 exemplified in the Natural History of this one 

 apparently insignificant little Sawfly, which is 

 the Architect of the Willow-apple gall. How 

 many millions of men have cast their eyes upon 

 these rosy little apples, that are in certain sea- 

 sons found in such prodigious abundance on 

 the leaves of the Heart-leaved Willow, without 

 even giving a passing thought to the very inter- 

 esting questions— "What makes these apples? 

 Why are they so abundant in certain seasons 

 and so scarce in others ? What prevents them 

 from increasing to such an extent, a? to entirely 

 eat up all the leaves on every Willow bush be- 

 longing to this particular species upon which 

 they occur, and thereby killing the entire bush? 

 What prevents them from swarming to this ex- 



