4 

 frequently obstructed by a webbing of silk mixed with yellowish grains of 

 excrement, called " f rass ". The greater part of the f rass is pushed out through 

 holes in the stem, where it clings in moist masses, sei'ving to indicate the posi- 

 tion of the borer within. The popular opinion seems to be that borers penetrate 

 directly to the central cavity of the main stem along which they work, feeding 

 at the walls of this cavity. This is not strictly the case. The larvae usually 

 work in the tissue surrounding the central cavity of the stem, and often do not 

 break through into this cavity until they are about half grown. 



One borer can usually find food for its complete development at the base of 

 the stem. When more borers are present, however, the mining is extended 

 along the main stem and I'unners, into the bases of the leaf-stalks and, in 

 rare instances, even into the fruit itself. Upon the death of one plant, the 

 larvae are able to transfer their activities to one nearby. 



GroAvth is completed in a month to six weeks, at the end of which time the full- 

 grown caterpillar deserts its burrow in the squash plant and enters the soil 

 nearby. After penetrating to a depth of from one to six inches it hollows out 

 a cell, spins its cocoon of tough black silk and, gi'adually shrinking within its 

 last larval skin, settles down to pass the winter. 



There is but one generation of the squash vine borer each year in New Eng- 

 land. It is partially double-brooded, however, in the latitude of New Jersey and 

 Southern Ohio and two full generations occur in Georgia and further south. 



Nature op Injury. 



In late July in Massachusetts, squash growers begin to notice plants Avith 

 wilted, drooping leaves. This condition may be the result of excessive feeding 

 in the root by larvae of the striped cucumber beetle. It is also a symptom of the 

 disease known as bacterial wilt. The chief cause of this wilting, however, is 

 found in the gradual destruction of the main stem of the squash jjlant near its 

 base by the tunneling of squash vine borer larvae, which may be detected by 

 the yelloAvish masses of frass which they push from their burrows. 



The base of the main stem frequently fails to support all the borers present, 

 and becomes a filthy, rotting mass, invaded by various sap-feeding beetles and 

 filth-loving insects. See Plate II, figure 4. It is finally reduced to a few 

 dried shreds, separated from the root by a light pull. See Plate II, figure 5. 



The elfect of squash vine borer infestation varies from a slight check in the 

 growth and productiveness of the infested vine, to its death outright, and the loss 

 of its partly-formed fruit. In the same field one may see a well-growTi, thj^ifty 

 vine which shows some borer injury, and nearby a dried, withered remnant of 

 a vine, the shredded and distorted base and hardened masses of frass testifying 

 to the cause of its death. A combination of factors is involved in this difference 

 in the effect of infestation. First, a thrifty vine can often support one or two 

 borers, while a less vigorous plant will be completely girdled. Second, plants 

 Avhich have been girdled do not always die. If the lainners have developed 

 far enough to " strike " numerous secondary roots from the nodes, and if 

 these roots can find sufficient moisture and food, the vine may yet produce a 

 fair crop. The crop is materially reduced, however, if not lost entirely in dry 

 portions of the field or in dry years, or when fertilization of a naturally poor 

 soil has been confined to the hill, as is so often the case. In the case of squashes 

 planted late, or having a slow early growth, in which the runners have failed 

 to root before the borers become half grown, the crop is very often a failure. 



Natural Enemies. 



No parasitic enemies of the adult moth have yet been recorded. It is the 

 chance prey, however, of certain large robber flies (Asilidae) which have been 

 observed to pounce upon the moths in the fields. The larvae in their tunnels in 

 the squash stem appear to have escaped parasites, but are sometimes attacked 

 by the larvae and adults of ground beetles (Carabidae). These agencies are of 

 little economic importance. 



The eggs of the squash vine borer are subject to a high degree of parasitism 

 by a tiny wasp of the family Scelionidae, the members of which are exclusively 

 egg parasites. The species has been identified by Mr. A. B. Gahan, of the 



